COSTA RICA FOREST RESEARCH PROGRAMME CRF · COSTA RICA FOREST RESEARCH PROGRAMME CRF Carate, Osa Peninsula, Costa Rica ... natural tracks in and near the riverbed. 4. To assess nest

COSTA RICA FOREST RESEARCH

PROGRAMME

CRF

Carate, Osa Peninsula, Costa Rica

CRF Phase 161 Science Report 1 January 2016 – 31 March 2016

Jenna Griffits, Charlotte Watteyn, Berglind Karlsdottir, Alex McCafferty, Aslheigh Arton, Alistair Ross, Joe Wilcox

CRF161 Griffiths J, Watteyn C., Karlsdóttir B., McCafferty A., Arton A., Ross A., Wilcox J.

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Staff Members

Jenna Griffiths (JG) Research and Operations Manager (ROM)

Charlotte Watteyn(CW) Principal Investigator (PI)

Berglind Karlsdottir (BK) Assistant Research Officer (ARO)

Alex McCaffety (AC) Assistant Research Officer (ARO)

Ashleigh Arton (AA) Assistant Research Officer (ARO)

Alistair Ross (AR) Field Communication Officer (FCO)

Joe Wilcox (JW) Conservation Apprentice (CA)


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Content 1. Introduction ................................................................................................. 5

1.1 Natural history of Costa Rica and its wildlife conservation .................... 5

1.2 Osa Peninsula ....................................................................................... 6

1.3 Aims and Objectives of Frontier CRF .................................................... 8

2. Training ..................................................................................................... 10

2.1 Briefing Sessions ................................................................................ 10

2.2 Science Lectures ................................................................................. 10

2.3 Field Training ...................................................................................... 11

2.4 BTECs, CoPEs and TEFLs during phase CRF161. ............................ 11

3. Research Work Programme ...................................................................... 12

3.1 Survey Areas ....................................................................................... 12

3.2 Projects .............................................................................................. 13

3.2.1 Estimating the Population Density of the Four Primate Species Coexisting ..................................................................................................... 13

Introduction ................................................................................................... 13

Material and Methods .................................................................................. 13

Results .......................................................................................................... 15

Discussion .................................................................................................... 15

3.2.2 Poison dart frog study .......................................................................... 15

Introduction ................................................................................................... 15

Material & Methods ....................................................................................... 16

Results .......................................................................................................... 19

Discussion .................................................................................................... 20

3.2.3 Mammal track study along Rio Carate, Osa Peninsula ........................ 23

Introduction ................................................................................................... 23

Material & Methods ....................................................................................... 24

Results .......................................................................................................... 26

Discussion .................................................................................................... 30

3.2.4 Turtle predation study along Carate and Leona beach, Osa Peninsula. ...................................................................................................................... 32

Introduction ................................................................................................... 32

Material and Methods ................................................................................... 33

Results .......................................................................................................... 35

Discussion .................................................................................................... 35


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3.2.5 Birds of Carate lagoon, a study on the species richness and abundance ...................................................................................................................... 36

Introduction ................................................................................................... 36

Material and methods ................................................................................... 37

Results .......................................................................................................... 38

Discussion .................................................................................................... 41

3.2.6 Bird species richness and abundance in primary, secondary and degraded forest ............................................................................................. 43

Introduction ................................................................................................... 43

Material and Methods ................................................................................... 45

Results .......................................................................................................... 48

Discussion .................................................................................................... 48

References ................................................................................................... 49


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1. Introduction

1.1 Natural history of Costa Rica and its wildlife conservation

Costa Rica, located between Nicaragua and Panama, is one of the seven Central American

countries and covers an area of 51.100 km2. It is surrounded by the Pacific on the west and the

Caribbean on the east, creating a coast line of 1103 km and 255 km respectively. Even though

this small country covers only 0.01 percent of the earth’s surface, it contains >4% of the

world’s biodiversity, including around 12,000 plant species, 1,239 butterfly species, 838 bird

species, 440 reptile and amphibian species, and 232 mammal species (Sánchez-Azofeifa et al.,

2002; IUCN, 2006; World Resources Institute, 2006; National Biodiversity Institute, 2007). The

high species richness has been attributed to two main factors; its geographical location and

climatic conditions. The fact that Costa Rica is situated between North and South America

means it can serve as a species corridor between these two continents. Furthermore, it lies

halfway between the Tropic of Cancer and the equator, leading to an annual average

temperature of 27 °C, with very little fluctuations throughout the year. Therefore, the seasons

in this area are defined by precipitation, not temperature, resulting in a distinct dry and wet

season. The dry season starts around November/December and continues through April/May,

after which the rainy season begins. The southern Pacific lowlands receive a particularly high

degree of average annual rainfall (about 7,300 mm) (Baker, 2012). Although more than one-

fifth of Costa Rica is protected, further action must be taken in order to raise, or at least

sustain the current level of biodiversity (World Resources Institute, 2006).

Costa Rica is one of the world’s leading countries in environmental sustainability and

conservation (Fagan et al., 2013), however, this has not always been the case. Like many other

countries throughout the world, Costa Rica has been the site of extensive deforestation over

the past few centuries. Up until the 1960s, activities such as logging and hunting seriously

threatened the biodiversity in this region, resulting in over half of the country’s forests being

cut down and many species being driven to the verge of extinction (Henderson, 2002). The

poaching of turtles for the fatty calipee and collection of turtle eggs for example, has severely

depleted populations of endangered black turtles (Chelonia mydas) and vulnerable olive ridley

turtles (Lepidochelys olivacea) that use Costa Rica’s coastlines as nesting sites. Similarly, the

hunting of Costa Rica’s wild cat species, peccaries and tapirs for their meat, skins and other

body parts, has significantly reduced wild populations. Since the 1960s, some of these issues


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have been controlled through the implementation of several reforestation programs,

legislation, education and the creation of protected areas, now representing almost 27% of the

country’s surface area (The World Bank Group, 2015). Costa Rican law currently protects 166

species from being hunted, captured and traded, yet illegal hunting still occurs, including in

protected areas (Baker, 2012). Deforestation and habitat fragmentation outside of the

country’s protected areas and national parks is still a significant problem due to expanding

human populations and related increases in economic pressure. Additionally, the projected

impacts of climate change are also likely to have significant adverse effects on Costa Rican

biodiversity (Baker, 2012). Due to the high levels of biodiversity and multiple threats placed on

Costa Rica it is important to conduct research to determine the health of the ecosystem and its

species. Massive deforestation and the resulting biodiversity crisis have already increased

awareness and interest in conservation of tropical habitats worldwide (Wilson, 1992), but the

real practice requires a basic understanding of the native fauna and flora; and since tropical

forests are not single, homogeneous, biotic formations (Gentry, 1990), the biodiversity of

these areas must be understood on a local, as well as regional, level.

1.2 Osa Peninsula

The Osa Peninsula is located in the southwest of Costa Rica and covers an area of 1093 km²

(Henderson, 2002). The peninsula contains the last remnants of tropical broadleaved

evergreen lowland rainforest on the Central American Pacific slope (Kappelle et al. 2002) and

has a very high species richness of about fifty percent of Costa Rica’s biodiversity.

Furthermore, this area inhabits several endemic species such as the Cherrie’s Tanager

(Ramphocelus costaricensis), the Red-backed squirrel monkey (Saimiri oerstedii)) and the Golfo

Dulce poison dart frog (Phyllobates vittatus). Since these and more species are only found in

this area, it makes the Osa Peninsula the ideal location for conservation research (Larsen &

Toft 2010).

Three main forest types can be found in the Osa Peninsula; Tropical Wet, Premontane Wet and

Tropical Moist forest, with elevations ranging between 200 and 760 m (Santchez-Azofeifa et

al., 2002). The variation in topography leads to a highly variable climate, with an average

annual rainfall of 5500 mm, a mean temperature of around 27 °C and humidity levels almost

never dropping below 90% (Cleveland et al, 2010). There are about 12,000 people living in the

Osa Peninsula, mainly settled in small and scattered villages. The most important sources of


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income in this region are agriculture (rice, bananas, beans and corn), livestock (cattle), gold

mining, logging and, more recently, the expanding eco-tourism industry (Carrillo et al., 2000).

The human population is increasing at a rate of 2.6% annually, which is incredibly high

compared to 1.3% in the rest of the country and 1.14% globally (Sánchez-Azofeifa et al., 2001).

As a result of the growing popularity of ecotourism, there has been a rise in the number of

hospitality business along the road, from Puerto Jimenez to Carate, since the 1990s (Minca and

Linda, 2002). This has caused growing concern for the sustainability of the region’s

environmental resource demands (Sánchez-Azofeifa et al., 2001).

The Frontier’s Costa Rica Forest Research (CRF) programme began in July 2009 in collaboration

with the local non-governmental organisation, Osa Conservation, based at the Piro site (N

08°23.826, W 083°20.564) in the southeast of the Osa Peninsula. In October 2015, Frontier

moved to Carate, located in the southwest of the Osa Peninsula. The site is a prime location for

carrying out both forest and shoreline surveys as there is relatively easy access to both the

primary and secondary forest, as well as pristine beach habitat. The long term objectives of the

project are to provide information on the dispersal and diversity of faunal communities in the

Golfo Duche Forest Reserve, with the aim of increasing protections and connectivity in the

area, whilst also investigating the effects of climate change, deforestation and other

anthropogenic impacts on the terrestrial communities of Costa. There are six core faunal study

groups within CRF; primates, sea turtles, wild cats and other mammals, Neotropical otters,

amphibians and reptiles and birds.


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Figure 1. Map of the Osa Peninsula, showing Carate, our area of study http://www.vivacostarica.com/costa-rica-

maps/costa-rica-maps-southern-pacific.html.

1.3 Aims and Objectives of Frontier CRF

Under the umbrella of the research program, the specific aims and objectives of Frontier CRF

are:

1. To estimate the population density, distribution and feeding preferences of the four

primate species present in Carate, Osa Peninsula, Costa Rica; and compare these

among the different habitat types present in this area.

2. To estimate the population density and distribution of Poison dart frogs in Carate,

more specifically in Leona Loop, using a mark-recapture method; and to see how

environmental changes affects the Poison dart frog population.

3. To assess mammal species richness and abundance along Rio Carate by searching for

natural tracks in and near the riverbed.

4. To assess nest success and turtle nest predation by conducting morning and night

turtle patrols along two beaches, Playa Carate and Playa Leona.

http://www.vivacostarica.com/costa-rica-maps/costa-rica-maps-southern-pacific.html

http://www.vivacostarica.com/costa-rica-maps/costa-rica-maps-southern-pacific.html


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5. To determine bird species richness and abundance in and around the lagoon of

pejeperrito in Carate; and to see how changes in environmental variables affect the

presence of these species.

6. To compare the bird species richness and abundance between primary, secondary and

degraded forests, by performing point counts along the different trails, focusing on 44

forest bird species selected on several criteria, such as endemism, IUCN status,

ecological function and migratory features.

7. *To gather information about the amphibian and reptile species richness in the

primary, secondary and degraded forests of Carate, Osa Peninsula, Costa Rica.

8. *To study to otter populations present along the rivers, streams and lagoons in Carate.

*The points in italic are the studies that are still in their initial phases and will be included

during the next science report (phase 2; April – June 2016).


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2. Training The volunteer Research Assistants (RAs) and newly appointed staff members receive a number of

briefing sessions on arrival (Table 1), followed by regular science lectures and field training (Table 2)

throughout their deployments. The CRF research program also supports candidates completing the

BTEC Advanced Certificate, Advanced Diploma in Tropical Habitat Conservation, the Certificate of

Personal Effectiveness (CoPE) and the Teach English as a Foreign or second Language (TEFL) (Table 4).

2.1 Briefing Sessions

All the people newly arriving to CRF get an introduction towards the aims of the research

programme, the methodologies used and the research output of the individual projects.

Furthermore, they get an update on the achievements of CRF through a general Science

presentation, this is an introduction to the Frontier Costa Rica Forest Research Programme in Carate.

Additionally, all volunteers and staff are given a health, safety and medical briefing, of which they are

tested on before participating in any field activity. Volunteers undertaking any kind of the previous

mentioned qualification courses are given an introductory briefing before they begin the

assessments.

Table 1. Briefing sessions conducted during Phase CRF151

Briefing Session Presenter

Introduction to the Frontier Costa Rica Forest Research Programme JG, CW

Health and Safety Briefing and Test CW, BK, AA, JW

Medical Briefing and Test CW, BK, AA, JW

Introduction to the BTEC, CoPE & TEFL Qualifications JG, CW

Introduction to Surveying and Monitoring ALL

Camp Life and Duties JG, CW

2.2 Science Lectures

A broad program of science lectures is offered at CRF, providing information and training the

different aspects of research going on in our study area. Lectures are presented using PowerPoint

and give a better understanding about the biology and ecology of the studied species. Furthermore,

they give an insight in the methods and data analysis used by CRF and considerations made when

planning research projects.

Lectures are scheduled with the following objectives:

To allow every volunteer and member of staff to attend each presentation at least once

during deployment, regardless of length of stay.

To meet the time requirements for BTEC assessments.


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To avoid conflict with other activities, maximizing attendance.

To provide detailed training on specific software and applications used in conservation, such

as GPS.

Attendance of lectures is compulsory.

Table 2. Science lectures delivered during Phase CRF161.

Science Lecture Presenter

Primates JW, AC

Terrestrial birds CW

Lagoon birds BK

Turtle patrol survey JG

Mammal tracks and GPS workshop JG

Climate change ALL

2.3 Field Training

All volunteers and newly appointed staff members receive field training. Training is hands-on and

provides an opportunity to become familiar with the field equipment used during surveys. These

sessions are hold before starting every survey, to inform volunteers and new staff members about

the way the survey is carried out and to assure accurate data collection. Both in the field and on

camp site, various identification books are present to teach how to identify flora and fauna species.

2.4 BTECs, CoPEs and TEFLs during phase CRF161.

Frontier offers volunteer Research Assistants an opportunity to gain internationally recognised

qualifications based around teamwork, survey techniques, environmental conservation and effective

communication of results. The BTEC in Tropical Habitat Conservation can be done in a four week

program (Advanced Certificate) or a ten week program (Advanced Diploma). Table 4 gives an

overview of the BTECs carried out during this phase.

Table 3. BTECs, CoPEs and TEFLs during phase CRF 161.

Name BTEC Title and Type Mentor

Aneira Williams Mammal species richness and abundance, a comparison between two trails Rio Carate and Atalea Loop. Goal: Aneira wanted to carry out a BTEC in order to start a Master’s degree in Conservation science.

JG, CW, AA

Name CoPE Title and Type Mentor

Nicole Huggins General CoPE certificate Goal: Nicole wanted to carry out a CoPE in order to get into the army as a logistic officer.

JG, CW


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3. Research Work Programme

3.1 Survey Areas

All the fieldwork is carried out in Carate, located in the southwest of the Osa Peninsula. The research

in this area has just began in November 2015. The landscape is heterogeneous, composed of lowland

moist primary, secondary and coastal forest, and disturbed forest. Dominant tree species include;

Ficus insipida, Ceiba pentandra, Attalea butyracea, Carapa guianensis, Castilla tunu, Spondias

mombin, Hyeronima alchorneoides, Chimarrhis latifolia, Fruta dorada, Caryocar costaricense, Ocotea

insularis, Pouteria torta, and Inga allenii. Mean annual rainfall and temperature for the area is 5,000-

6,000 mm and 26-28 °C respectively; the dry season extends from the end of December until March.

Different trails have been selected, including the different types of habitat and with different degrees

of usage and disturbance (table 1). These trails are used as survey transects for our eight different

projects. Most of the trails are narrow and machete-cut. We are still not fully sure about the exact

habitat types present in our trails, for example, it is highly possible that Luna ridge contains a mix of

primary and secondary forest. In order to assess this in more depth we are currently undertaking GIS

work and also require in-depth habitat studies, perhaps with the help of drones to get more

knowledge about all the different habitat types present in Carate and surroundings.

Table 4. Current trails used for the research carried out in Carate S coordinates of the start and the end of the trail, as well as the length (km).

Trail Name (code) Transect Length (km)

GPS Coordinates START trail

GPS Coordinates END trail

Disturbed forest

Attalea Loop 08º26'11.14 N 83º26'16.99 W

08º26'29.60 N 83º29'02.37 W

Road 08º26'28.37 N 83º26'25.73 W

08º26'28.11 N 83º27'16.33 W

Beach Trail 08º26'36.69 N 83º27'49.54 W

08º26'50.30 N 83º29'02.37 W

Secondary forest

Shady Lane

Leona Loop 08º26'56.09 N 83º29'04.37 W

08º26'56.39 N83º29'05.16 W

Rio Carate 08º26'33.01 N 83º27'23.26 W

08º27'37.30 N83º27'48.69 W

Primary forest

Leona Ridge 08º26'48.19 N 83º28'52.97 W

08º26'54.51 N83º29'05.16 W

Luna Ridge 08º26'29.63 N

83º27'16.62 W

08º26'28.54 N 83º26'56.86 W

We are very close to the Pacific ocean, and use the two beaches, Playa Carate and Playa Leona for

our turtle patrols. There is also the river Rio Carate passing through our survey areas, bordering the

National park of Corcovado, and has an important function in providing water and food for animals

when they move out of the park.


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3.2 Projects

3.2.1 Estimating the Population Density of the Four Primate Species Coexisting

Introduction

Throughout Costa Rica, four different primate species can be found; the Central American squirrel

monkey (Saimiri oerstedii), the mantled howler monkey (Alouatta palliata), the geoffroy’s spider

monkey (Ateles geoffroyi) and the white-faced capuchin (Cebus capucinus). The Osa Peninsula is the

only part of Costa Rica where these four new world primate species occur together, making this place

a very interesting area for study (Carrillo et al., 2000). Primates are predominantly frugivorous,

therefore, they have an important ecosystem function as seed dispersers, making them vital for

maintaining the plant diversity within the forest (Julliot, 1997; Garber et al., 2006). Generally,

primate species are highly sensitive to land conversion for agricultural purposes and development,

clear cutting, selective logging, hunting and the pet trade (Cropp and Boinski, 2000). In Costa Rica,

primates are mainly threatened by increased rates and amounts of forest loss and fragmentation,

and infrastructural changes for the country's booming tourism industry. In Panama, they have fared

even worse since deforestation has been extensive and unregulated (Boinski & Sirot 1997; Boinski et

al. 1998). The development of agribusinesses for oil palm and banana plantations is a serious

component of habitat destruction and fragmentation. Logging roads, clearings for telephone and

electric power lines, or other practices leading to forest fragmentation restrict populations to smaller

forest areas, decreasing their ability to find food during times of the year when food abundance is

lowest (e.g. dry season) and leading to declines of genetic diversity, which in turn affects the

population health and stability (Boinski et al. 1998).

Since October 2016 Frontier CRF has been surveying the presence of the four primate species in

Carate. The overall research aim is to gain more knowledge about the distribution of the four primate

species in this area of the Golfo Duche Reserve. By comparing the richness and abundance of primate

species between the different habitat types, we can gain more information regarding management

and policy decisions on a local level. Until now, density estimates are lacking for the Central

American squirrel monkey and the white-faced capuchin, which makes them key to survey, however,

focus is also places on the red listed spider monkey and squirrel monkey.

Material and Methods

The Central American squirrel monkey (Saimiri oerstedii) is one of the five species of squirrel

monkeys. Their status on the IUCN list is Vulnerable, with decreasing populations (IUCN, 2008). The

http://pin.primate.wisc.edu/factsheets/glossary#157

http://pin.primate.wisc.edu/factsheets/glossary#161


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main threats are habitat loss due to logging and agriculture. They inhabit the lowland rainforests of

Pacific Costa Rica towards Western Panama. They are arboreal and diurnal species, depending on a

diet of insects, leaves, fruits, barks, flowers and nectar, and foraging in the low and middle levels of

primary and secondary forests. Group sizes range from 20 to 75 individuals that are travelling

between 2.5 and 4.2 km per day (IUCN, 2008). The white-headed capuchin (Cebus capucinus), also

known as the white-faced or white-throated capuchin, has a very important ecological function

within the forest ecosystem by dispersing pollen. They are Least Concern on the IUCN list but their

main threats include tree logging and clear-cutting because these activities drastically reduce suitable

habitats. Other threats include the capturing for the pet trade and hunting for their meat. Like the

squirrel monkeys, the capuchins are diurnal and arboreal species with a diet of mainly fruits and

insects. They range from Honduras all the way down to Ecuador and are highly adaptive species,

meaning they can occupy various habitats, but usually occur in tropical evergreen and dry deciduous

forests. Their group size ranges from 4-40 individuals, with a mean average of 16 and they travel on

average 2 km a day (IUCN, 2008). The Golden mantled howler monkey (Alouatta palliata) are found

in Costa Rica, Nicaragua, Panama and Guatemala, mostly in the older areas of evergreen primary

forest as well as secondary and semi-deciduous forest. They have an important function as seed

dispersers and germinators and their dung is an important food source for several dung beetle

species. Their status on the IUCN list is Least concern (IUCN, 2008). They are diurnal, arboreal species

with a diet that mainly consists of leaves, giving them low amounts of energy which makes them

resting during most of the day. Their main threats are forest destruction and fragmentation. The

group size ranges from 10-20 individuals, but can reach up to 40 individuals. The males are

characterized by a very obvious white scrotum when they reach sexual maturity and have an enlarge

hyoid bone which allows them to create a loud howling noise, usually displayed at dawn and dusk

(IUCN, 2008). The Geoffroy’s spider monkey (Ateles geoffroyi) is native to Costa Rica and Panama and

is currently Endangered with a decreasing population (IUCN, 2008). They are diurnal and arboreal

species, mainly inhabiting the upper layers of the forest, and have a diet of fruits, leaves and

sometimes insects, seeds, barks and flowers. Their threats are habitat loss and hunting for their meat

and the pet trade. The group size ranges from 20-40 individuals that are living in a fission-fussion

society, meaning that they split into subgroups during the day and congregate again during the night

(IUCN, 2008).

Data is collected by walking six different trails (Beach trail, Road, Attalea loop, Luna ridge, Leona

loop, Shady lane) and conducting total counts of all the primates encountered. The surveys started

between 05.30 and 06.00 am, to cover peak primate activity and thus increasing detection

probability. A minimum of three observers are walking at a constant speed of 2 km/h, including


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regular stops every 100m as recommended by Peres (1999). The six trails are divided into three main

habitat types; primary (Luna ridge, Leona loop), secondary (Beach trail, Shady lane) and degraded

(Road, Attalea loop) forests. Each trail is walked in one way, and this not more than once a week. The

surveys are done in fair weather because of reduced detection probability in adverse weather

conditions. Since phase one is in the middle of the dry season, we didn’t have problems with

cancelling surveys because of adverse weather conditions. When encountering a monkey troop, an

observation time of maximum 30 minutes was set. This gives us enough time to assure a reliable

count of all the individuals without disturbing them for too much time (Pruetz & Leasor 2003). All

individuals seen at the same time and exhibiting the same general behaviour (e.g., resting, moving or

foraging) were considered to be part of the same group (Chapman et al., 1995). Where possible,

secondary data on group composition (i.e. gender and age group; adult, juvenile, infant) was also

recorded. Furthermore, the behaviour (e.g. resting, moving or foraging) upon encounter, the

duration of observation, the perpendicular distance from the trail to the geometric centre of the

group at first sighting, height of the group in the tree and direction of travelling was noted. This study

was non-invasive and according to the legal requirements of Costa Rica (Costa Rican Government

Decree 31514-MINAE). Any kind of abnormal or aggressive behaviour towards the observers by

individual primates was responded to by moving on as quickly as possible.

Results

In progress. We recently changed the methods for primates. Instead of focusing on their home

ranges (see science reports of 2015), we want to start a general study on their distribution and

compare the richness and abundance among the different types of habitat. Therefore, we first need

to carry out more research about the best suitable methods, for example, the use of line transects,

and a laser range finder to make better estimates about the distances of the primate groups from the

observation point on the trail, etc. This will involve a more in-depth literature study during the next

phase in which we hope to implement the new methods.

Discussion

In progress.

3.2.2 Poison dart frog study

Introduction

Worldwide, human activities are having negative effects on natural environments and the species

they inhabit. Since most amphibian species have small geographical ranges, they are likely to be the

http://soltiscentercostarica.tamu.edu/sites/default/files/NormasGenerales.pdf


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major group at risk. Thanks to the now-general understanding that most of the amphibian species

are at risk, they have received more attention during the last two decades (Stuart et al., 2004). About

one-third of the 6,300 known species are currently threatened with extinction due to a combination

of habitat destruction and degradation, the spread of virulent diseases, pollution, climate change and

the pet trade (Wake & Vredenburg, 2008; ZSL, 2016). They are highly sensitive to environmental

changes, leading to population decreases and even extinctions (ZSL, 2016).

This study focuses on the green and black poison dart frog (Dendrobatus auratus), which is one of

more than 200 poison dart frog species. Because of their toxicity, poison dart frogs have only one

predator; Leimadophis epinephelus, a snake species that has built up resistance over time. The bigger

and more widespread threat for poison dart frogs is the logging and clearing of the rainforests,

causing a decline and dry-out of their natural habitat. Air and water pollutants also have tremendous

effects on the growth and reproduction of the frogs, by polluting the environment in which they live,

reducing their food supply, and negatively affecting their immune system. Furthermore, like other

amphibian species, poison dart frogs are threatened by the fungal disease Chytridiomycosis. This

fungus is possibly causing the biggest loss of biodiversity recorded in history. The bright colour of the

poison dart frogs strikes the attention of having them as pets, leading to the illegal catching and

worldwide trading of poison dart frogs. Climate change is a more recent threat, whereby

temperature and sea level rises, droughts and extreme weather events are affecting their time of

breeding, skin moisture and egg survival (reference). Many poison dart frog species are decreasing in

population sizes, and some of them are now classified as Endangered (IUCN, 2008). The aim of this

study is to start long-term research on the population size and distribution of D. auratus in an

evergreen primary rainforest, located on a south facing slope near the Pacific coast adjacent to La

Leona beach, Carate, Osa peninsula, Costa Rica. By using a mark-recapture method based on

photographs of the unique pattern, we want to get an estimate of the population size of D. auratus

present in this area. Furthermore, we want to examine how environmental parameters, such as

habitat characteristics, weather, light intensity, soil moisture and temperature, influence the

presence of this species of poison dart frog.

Material & Methods

The species under study is Dendrobates auratus (Dendrobatidae family), better known as the green

and black poison dart frog. D. auratus belongs to the Dendrobatidae family, which is one of the two

poison dart frog families. Both Dendrobatidae and Aromobatidae families are native to the

rainforests of Central and South America. About a quarter of the more than 200 poison dart frog

species are listed as threatened or critically endangered. The green poison dart frog is listed as Least


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concern on the IUCN list (IUCN 2016). Adults are marked with contrasting green coloured bands and

spots on a black background, and are usually about 25-39 mm and 27-42 mm in length for

respectively males and females (IUCN 2016). They can reach the age of eight years, but is much lower

in the wild (Leenders, 2001)They are arboreal and terrestrial diurnal frog species, meaning they are

actively foraging during the day by moving in hops on the ground or in large buttressed trees (Guyer

& Donnelly, 2005). They are native to the humid lowland and submontane forests of Costa Rica,

Panama, Nicaragua and Columbia (Leenders, 2001; Savage, 2002; Caldwell & Summers, 2003; Guyer

& Donnelly, 2005). However, they have been introduced in similar habitat types in e.g. Hawaii, to

control non-native insect pests. Poison dart frogs produce powerful skin alkaloids, which are used for

defence purposes, by consuming toxic ants and store these alkaloids in their skin. The brighter the

coloration, the higher the amount of alkaloids present in the skin. Females actively compete for

males and lay about four to six eggs in the nest made by the chosen male (Savage, 2002; Guyer &

Donnelly, 2005). Males can mate with up to six females and show a high degree of paternal care,

taking care for the offspring of different females simultaneously (Savage, 2002; Caldwell & Summers,

2003). After oviposition upon leaf-litter, the male guards and takes care of the clutch by regular

visits, removing fungus and rotating the eggs (Silverston, 1975; Schafer, 1981; Heselhaus, 1992).

Upon hatching, the males carry the tadpoles towards stagnant water bodies in a tree hole, the leaf

axil of a bromeliad, or a small ground pool (van Wijngaarden, 1990).

The fieldwork is carried out on the Leona Loop trail, which is located in primary lowland rainforest

habitat (Figure …). The reason for studying this area evolves from a previous BTEC, focusing on the

home range of the green and black poison dart frog in a habitat of which it was sure to encounter a

decent amount of individuals. The trail was initially divided into 11 sectors in order to get an idea of

their home ranges. We are now carrying on this study, but focusing on the population density on

Leona Loop. During the survey, two observers are walking in front and spot all the frog individuals on

the path as well as one meter alongside the path, in the leaf litter, on tree logs and in the trees. Two

other observers in the back are slightly poking the leaf litter with a stick, again up to one meter along

the path to look for individuals that might be missed out by the two persons in the front. Since this is

a mark-recapture study, all individuals seen along the trail are ‘marked’ by taking a picture of the

back and legs. Using invasive techniques for marking anurans has been strongly debated during the

last years based on ethics, public opinion, infection risk and impacts on behaviour and survival of the

marked individuals. Photographing the distinguishable markings that remain constant through time is

a possible alternative for identifying the different individuals present in area (Kenyon et al., 2009).

The pictures have to be taken from above to be sure the back pattern is clearly visible. Poison dart

frogs distinguish themselves from one another by the green pattern on their back and legs, that


18

serves as a sort of fingerprint. Furthermore, each time an individual is spotted, information about

canopy cover, percentage of shade and habitat in which they are found are written down, as well as

the weather of the previous and present day. Back home, the pictures are compared with previous

ones to see if we have new are recaptured frog individuals. The study was non-invasive and

according to the legal requirements of Costa Rica (Costa Rican Government Decree 31514-

MINAE). The owner of La Leona Lodge, Adrian Morales Polanco, gave us the permission to start a

study on his land. Field staff just need to introduce the new volunteers the first time they come on

his land. Since we are not using camera traps or physically catching the frogs, we don’t need any kind

of government permits.

Figure 2. A map of the trail, used for the poison dart frog study, with the division into the different sectors.

We use the program MARK, a Windows or XP program providing parameter estimates from marked

animals when they are re-encountered at a later time. Usually, re-encounters can be from dead

recoveries (e.g. the animal is harvested), live recaptures (e.g. the animal is re-trapped or re-sighted),

radio tracking, or from some combinations of these sources of re-encounters. In our case, the

individuals are not physically captured and marked since amphibians are very sensitive towards

manual handlings, and our frog species is highly poisonous. Instead, pictures of the back and legs are

taken and identified back on camp to check if we have a new individual or a re-encounter. The time

intervals between re-encounters are about one week (time-unit). The basic input to the program

MARK is the encounter history for each frog individual. In this way, we are able to estimate the

encounter probability (p) and the survival rate of the population (phi). The population density is

estimated by using the formula:

N = ( ) / R; with (1)




19

- N = estimated population density - k = amount of surveys (1 to 16) - C = number of captures - M = cumulative number of unmarked captures - R = total number of recaptures

Results

The survival rate (Phi) is estimated at 0.9154318, which is very high (Phi lays between 0 and 1). This

means that the individuals within our population have a chance of 91.5% to survive from one sample

(survey) to the other. The encounter probability (p) is changing over the surveys. In the beginning,

the encounter probability is quite high, varying between 0.3345101 and 0.5258023. From survey 8

onwards, the encounter probability decreases and fluctuates around 0.20. From this we can say that

during the first couple of surveys we encountered more of the same frogs, whereas during the last

surveys we recaptured less and saw more new frog individuals. Table … gives an overview of the Phi

and p values, with their standard errors and lower/upper 95% confidence intervals.

Table 5: Overview of the parameter estimates Phi and p, and their standard errors and lower/upper 95% confidence

interval.


20

Figure 3. Graph showing the frog encounter probability throughout the surveys.

Based on the formula (1) described in the Materials and Methods section, we could estimate the

population density of green and black poison dart frogs in Leona Loop in Excel. So far, the density of

the population is estimated at 83.65625 individuals.

Discussion

During this first phase of the poison dart frog study in Leona Loop, we can say that 1) there is a very

high survival rate within the population, 2) the encounter probability changes over time, with more

of the same frog individuals recaptured during the first surveys than later on, and 3) the population

density so far is estimated at 83 individuals.

The high survival rate can be explained by the fact that the population in Leona Loop is very healthy

at the moment and that the environmental conditions are very positive in and around Leona Loop.

The fact that the poison dart frogs do not have natural enemies in this area also explains their high

level of survival. As mentioned before, the green and black poison dart frog has only one natural

enemy, Leimadophis epinephelus, who is not present here. Furthermore, the high survival rate also

indicates that our presence (noise and disturbance of the leaf litter) during the surveys does not give

a big amount of stress to the frogs and does not negatively impact the frog population. The fact that

we encounter more of the same frog individuals during the first surveys then at the end, might be

due to our survey effort. During the whole period of phase one, there was a change in staff working

on the project. Some people are better in spotting frogs then others, and it also takes some time to

learn where to look for the frogs. This can explain the higher amount of new frog individuals at the

end of the period. Observers (mainly the long-term field staff members) gained more skills in finding

the frogs compared with the time when they first arrived. Besides the change in encountering frogs

0

10

20

30

40

50

60

0 2 4 6 8 10 12 14 16

Enco

un

ter

pro

bab

ility

(p

) (%

)

Survey

Encounter probability


21

throughout the surveys carried out during phase one, there can also be a change during the survey

itself; with observational concentration being very high at the start of the survey and lowering down

by the end, causing a drop in frog encountering. During the next phase we will start to alter carrying

out surveys starting at sector one, and starting at sector 10. In this way we will be able to compare

where most of the frogs or found and see if there actually is an effect of the observers’ concentration

on the amount of encountered frogs. It is also possible that the frogs changed their behaviour upon

changes in environmental conditions (reference). They could be moving to other areas, or higher up

in the trees where it is less obvious to encounter them. The fact that we saw more new individuals by

the end, can be explained by the first rains coming in, so frogs coming back to the area, or juveniles

that are adults now and coming down from the trees (reference).

The population density so far is estimated around 83 frog individuals, which is quite low for

amphibians (reference). We are now during the dry season, and the dryer environment could have

stimulated some frogs to withdraw beneath damp leaf litter, thus reducing the number of exposed,

observable frogs and the density estimates recorded during this phase of the project. Previous

studies have shown that poison dart frogs use water from small pools of rainwater among the leaf

litter (Vences et al., 2000; Jowers & Downie, 2005). There was almost no rain during the last three

months, which can explain our low population density estimate. Furthermore, the fact that

Dendrobatids lay their eggs on the land and carry their larvae to small pools of water in the folds of

leaves, supports the random and independent distribution of poison dart frogs in the area (Miller,

2007). Poison dart frogs have been randomly observed in Carate, along the beach trail andshady

lane, etc. This is interesting regarding further research about the poison dart frogs in this area, in

which we might not only focus on Leona loop, but include other trails as well.

Studies have shown that D. auratus has bimodal peaks of activity, around 7am and 5pm (Jaeger &

Hailman, 1981; Graves, 1999; Miller, 2007). The high activity during the early morning is a product of

multiple factors. Environmental conditions are more favourable thanks to higher ground moisture

levels from unevaporated rainfall during the night, lower light and temperature levels, leading to

lower rates of evaporative water loss. Furthermore, during this time of the day, arthropod activity

might be higher, allowing frogs to forage more easily (Basset et al., 2001). Taking this into account,

we will commence our study of the poison dart frogs 30 minutes earlier (at 7am instead of 7.30am),

and carry out surveys late in the afternoon as well. However, this has to be logistically possible (5pm

is late to start a survey, and it is possibly too dark to return from Leona to Carate after the survey).


22

To account for the impacts of abiotic factors on frog sighting frequencies, the proximity to water, as

well as correlations with rainfall (humidity), air and ground temperature, light intensity need to be

considered. Especially rainfall and time of the day have both been identified as influencital factors,

with some poison dart frogs occurring in larger quantities in the presence of rain because of the

higher humidity percentage (Graves, 1999). We are currently looking at placing some HOBO’s in

Leona loop, to start measuring these environmental parameters in order to gain more knowledge

about how the environment affects the presence of the poison dart frogs in this area.


23

3.2.3 Mammal track study along Rio Carate, Osa Peninsula

Introduction

In general, protected areas are the backbone of conservation and are supposed to safeguard the

species inside the area. However, many protected areas don’t function in the way they should (e.g.

Caro & Scholte, 2007; Russel & Cuthill, 2009; Craigie et al., 2010). Effective protection to maintain

healthy species richness and abundance can vary with the location and size of the area. Furthermore,

abiotic and biotic as well as indirect and direct human activities occurring close to the borders of the

reserve, such as firewood collection, cattle grazing, bush fires, fishing and hunting, are affecting all

the organisms living in or crossing the periphery of the reserve (Laurance, 2010). With increasing

human disturbance, mammals often move to the central parts of protected areas while areas closer

to the park boundaries may be less attractive due to the negative effects of human activities along

the edges. Despite the fact that these so-called edge effects can have big consequences regarding

conservation issues (e.g. Primack, 2010), this topic has received little attention. Most of the studies

have been focusing on large carnivore species (e.g. Revilla et al., 2001; Slotow & Hunter, 2010),

showing that their large individual home ranges are extending the boundaries of the decreasing

reserve areas, leading to a movement outside the reserves via buffer zones. However, the threats

outside the reserves, block these species to move out of the reserve. Instead, they often have to

move back towards the centre, leading to population declines due to habitat and food competition.

Despite protective legislation, these kind of human-wildlife conflicts are common throughout Central

and South America (Zimmermann et al. 2005), as natural habitats are still being converted for

agricultural purposes and resource extraction, and poaching activities are still present along the

reserve borders (Cavalcanti & Gese 2009).

Estimating the distribution and abundance of mammals is not that easy. Especially in the case of the

Osa Peninsula, where big mammals are extending their home ranges from Corcovado National Park

towards other areas within the Osa Peninsula. This makes it even more vital to conserve and manage

these areas and the biological corridors that connects them. Information on the distribution is also

vital for the introduction of education and awareness initiatives, with the aim of preventing human-

wildlife conflict that threatens mammal populations and livelihoods across the species range

(Zimmermann et al. 2005). The aim of this study is to estimate the mammal species richness and

abundance along the river Rio Carate, which is located at the border of Corcovado National Park, the

Osa Peninsula, Costa Rica. Corcovado National Park compromises primary lowland rainforests, and

serves as an important haven for various animals and plant species. However, for many mammal

species, the area of the park is not sufficient to maintain healthy populations. By using tracking


24

techniques, we can gain knowledge about the mammal species present in and along the border of

the park, and it will give us an idea of which mammals are moving in and out of the park. This is

especially important for feline species, since their broad distribution ranges obligate them to move in

between different protected areas in order to not override their maximum carrying capacities.

Material & Methods

Tracking mammals by following footprints is probably the oldest known method of identifying

mammal’s presence in an area (Bider, 1968). Track surveys are efficient and usually low in cost, but

are dependent on suitable field conditions and trained observers (Burnham et al, 1980; Smallwood &

Fitzhugh, 1995). Track searches were performed along the river Rio Carate, Carate, Osa Peninsula,

Costa Rica; starting at the river estuary, and going two kilometres upstream. The surveys were

carried out during dry season, allowing us to walk and look for tracks in and around the riverbed. We

started at 7:00 am to prevent tracks from begin vanished. More than 200 mammal species are

currently present in the different forest types of Costa Rica. This study focuses on 20 mammal

species. Table 6 gives an overview of the 19 selected mammal species. All species are found in the

lowland rainforests of the Osa Peninsula (Cavalcanti & Gese, 2009). Among the focal species’

distribution range, only the Baird’s tapir is listed as Endangered. Many other mammal species are

listed as globally Vulnerable or Near threatened (IUCN, 2014). However, in Costa Rica, the six feline

species, Neotropical river otter and Paca are considered to be Endangered (Cavalcanti & Gese, 2009).

All mammal tracks were recorded and identified by measuring its widest point and the vertical

distance from the toes to the palm pad (Figure …) and by using mammal track sheets (Adapted and

modified of Sanchez, 1981). The GPS position of the track was noted down as well as the direction of

movement. This gives us information about the movement of individuals within a certain species. If a

track of the same species was found within 100 m from the previous track, it was not recorded since

it would probably be the same individual. Due to the very dry substrate, which is a mix of sand and

rubble, a considerable level of skills is necessary in order to accurately detecting and identifying the

tracks.

Finally, the program Estimate S allowed us to make an estimate about the mammal species diversity.

With this program, we are able to estimate the Simspon’s diversity Index, which is essentially the

probability of two randomly chosen individuals (tracks) being from different species. Furthermore,

we could make an estimate of the evenness, which show how evenly distributed the abundance of

the species is in the area.


25


26

Table 6. Overview of the 20 selected mammal species (IUCN, 2014).

Common species name Latin species name IUCN status Costa Rica status

Baird’s tapir Tapirus bairdii Endangered Endangered

Collared peccary Peccari tajacu Least concern Least concern

White-lipped peccary Tayassu peccary Vulnerable Endangered

Red brocket deer Mazama Americana Data deficient Data deficient

Tayra Eira Barbara Least concern Least concern

Neotropical river otter Lontra longicaudis Data deficient Endangered

Striped hog-nosed skunk Conepatus semistriatus Least concern Least concern

Common opossum Dedelphis marsupialis Least concern Least concern

Water opossum Chironectes minimus Least concern Least concern

Northern tamandua Tamandua Mexicana Least concern Least concern

White-nosed coati Nasua narica Least concern Least concern

Crab-eating raccoon Procyon cancrivorus Least concern Least concern

Central American agouti Dasyprocta punctate Least concern Least concern

Paca Agouti paca Least concern Least conern

Nine-banded armadillo Dasypus novemcinctus Least concern Least concern

Puma Puma concolor Least concern Endangered

Ocelot Leopardus pardalis Least concern Endangered

Jaguarondi Puma yagouaroundi Least concern Endangered

Margay Leopardus wiedii Near threatened Endangered

Jaguar Panther onca Near threatened Endangered

Figure 2. Standard measurements taken; A- Track widest point and B- vertical distance from the toes to the palm pad.

Results

During this first phase of the mammal track project, we have already some results to show. In total,

over the 13 different surveys, we saw 17 different species, of which one unidentified species and one

unknown cat species. The 15 identified species of our list were: water opossum, common opossum,


27

Neotropical river otter, collared peccary, white-lipped peccary, tayra, ocelot, crab-eating raccoon,

white-nosed coati, Central American agouti, nine-banded armadillo, baird’s tapir, red brocket deer

and margay. The overall abundance is 101; meaning that in total we saw about 101 different

individuals over the 13 surveys. The mean species count per sample (or in our case survey) is 4.69;

meaning that on average we see about four different species each survey. The amount of tracks we

saw of each mammal species is given in figure 4. Most of the tracks were from the Neotropical river

otter, followed by the ocelot, Bairds tapir, crab-eating raccoon and white-nosed coati.

Figure 4. Graph representing the amount of tracks found per mammal species over the 13 surveys.

Figure 5 shows that the cumulative number of species encountered (y) levels off with the cumulative

number of samples (surveys) carried out over time (x). However, after carrying out a rarefaction, we

see that the curve does not level of that much towards the end, meaning that we probably have not

reached the maximum amount of species present in this area yet.

Rarefaction: A statistical interpolation method of rarefying or thinning a reference sample by drawing random subsets of individuals (or

samples) in order to standardize the comparison of biological diversity on the basis of a common number of individuals or samples.

Species accumulation curve: A curve of rising biodiversity in which the x-axis is the number of sampling units (individuals or samples) from

an assemblage and the y-axis is the observed species richness. The species accumulation curve rises monotonically to an asymptotic

maximum number of species.

0 2 4 6 8

10 12 14 16 18 20

Enco

un

tere

d t

rack

s

Mammal speices

Encountered mammal tracks per species


28

Figure 5. The species accumulation and rarefaction curve.

Table 7. An overview of the species count, cumulative species count, abundance and cumulative sample number. The

species count gives the amount of species found in each sample (survey). The cumulative species count adds the amount of

species found in sample x to the amount of species found in sample x-1. The abundance gives the amount of individuals

over all the species found in each sample. The cumulative sample number gives the amount of samples (surveys) carried

out during the period.

Sam

ple

1

Sam

ple

2

Sam

ple

3

Sam

ple

4

Sam

ple

5

Sam

ple

6

Sam

ple

7

Sam

ple

8

Sam

ple

9

Sam

ple

10

Sam

ple

11

Sam

ple

12

Sam

ple

13

Tota

l

Species count 5 6 4 4 6 3 5 7 7 3 4 3 4 4,69

Cumulative species count 5 10 10 11 13 14 14 14 16 16 16 16 17 17

Abundance 5 6 8 5 8 5 9 22 14 3 7 4 5 101

Cumulative sample number 1 2 3 4 5 6 7 8 9 10 11 12 13 13

Figure 6 gives us the extrapolated species accumulation curve, showing us the equation from which

we can now estimate how many surveys we need in order to observe the maximum amount of

species present in the area. Table … shows us the amount of species we will have throughout the

surveys. So far, we carried out 13 surveys, which gave us 17 species. Based on the formula, we would

have seen around 19 species; which shows that the equation gives us a good estimate on how it is in

reality. If we then, based on the equation, try to estimate how many surveys we need to see a level

off in the amount of species, we fill in e.g. 20 or 30 surveys (=x in the formula), and we see that the

amount of species (=y in the formula) does not stabilizes since the formed equation is a linear

function. This will be discussed later on.


29

Figure 6. The extrapolated species accumulation curve with an equation that gives the relationship between the species

richness and the number of samples (surveys).

cumulative sample number cumulative species number log(cumsampleNo) log(cumspeciesNo) y2 10^(y)

1 5 0 0,69897 0,7838 6,07855

2 10 0,30103 1 0,91911 8,300667

3 10 0,477121 1 0,99827 9,960153

4 11 0,60206 1,041393 1,05443 11,33512

5 13 0,69897 1,146128 1,09799 12,53104

6 14 0,778151 1,176091 1,13358 13,60126

7 14 0,845098 1,176091 1,16367 14,57711

8 14 0,90309 1,176091 1,18974 15,47886

9 16 0,954243 1,230449 1,21273 16,32045

10 16 1 1,230449 1,2333 17,11197

11 16 1,041393 1,230449 1,25191 17,86101

12 16 1,079181 1,230449 1,26889 18,57342

13 17 1,113943 1,255273 1,28452 19,25385

20 1,30103 1,36861 23,36754

30 1.477121 1.44777 28

Furthermore, the output of Estimate S enables us to give an estimate of the species diversity, such as

the Simpson’s diversity index. The Simpson’s mean (D) is 8.21, and from this we can calculate the

Simpson’s mean index (1-D) with the formula 1-D = 1-(1/D) = 0.878197. Since this is close to 1, it

means we have a high mammal species richness over all the samples (surveys). Using the Simpson’s

diversity index, we can measure the evenness (E) with the formula E = (1/D)/S, with S the amount of

samples (surveys). The result is 0.631538, which is closer to 1, meaning that Rio Carate is

characterized by a quite high evenly distributed abundance of species.

y = 0.4495x + 0.7838

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0.2 0.4 0.6 0.8 1 1.2

Log

Cu

mu

lati

ve S

pec

ies

Nu

mb

er

Log Cumulative Sample Number

Extrapolated Species Accumulation Curve


30

Discussion

From our results so far, we can say that there are 17 mammal species present and active around Rio

Carate. Since we have only carried out 13 surveys, we cannot say that this is the maximum amount of

mammal species we can found over here. Our extrapolation curve does not level off at the end,

meaning that the equation formulated out of the extrapolation curve is a linear function. Based on

this equation, we cannot calculate how many surveys we need in order to reach the maximum

amount of species. Further research is necessary to get a better equation (e.g. logarithmic equation).

Most of the tracks were identified as Neotropical river otter, which can be mainly explained by the

fact that we are surveying along the river Rio Carate. It is still interesting to see that even though it is

dry season, there are still quite a few otters present in the area. During dry seasons, mammals tend

to move to other places to look for more favourable habitats. They have to look for water and food

resources that they are not finding in the areas they used to live during the wet season. We also saw

quite a lot of tracks from the Ocelot, Bairds tapir, Crab-eating raccoon and White-nosed coati. The

presence of feline species tracks, such as the ocelot, shows that wild cats are moving in and out of

Corcovado National Park. However, more data and analysis is needed to figure out how abundant

they are and to which areas they are moving to and from.

The data during phase one was collected during dry season, probably affecting the encounter

probability as it is thought that mammals move deeper into the centre of a protected area (in this

case Corcovado National Park), looking for food and water resources (reference). In general, the

composition of mammal communities depends on the forest’s ability to support the requirements of

the mammals present in the area. Modification of habitats, such as temporal or spatial changes, may

generate boundaries for species due to the newly created patchiness in the landscape, and this has

effects on the structure and dynamics of all biological communities (Cadenasso et al., 2003). Surveys

carried out over the whole year, will make it interesting to see if there is a difference in the amount

of mammal species and abundance we see during the wet and dry seasons.

During the following phase, we would like to make some changes in our study. Instead of only using

natural mammal tracks, we will use the track boxes of a previous BTEC student and place them

higher up the river since observational walks have shown that there are more tracks present higher

up. We will also continue to collect data from natural tracks, but will extend our trail higher up the

river as so far, we only cover a length of about 2 km. Furthermore, many mammals are shy and

elusive creatures, and their adaptation to live in the undergrowth or canopy, or their nocturnal


31

lifestyle makes detection difficult (reference). Over the years, wildlife biologists have used various

tracking techniques to assess mammal populations. The most common method is to detect the tracks

left in fine soil or sand (Olifiers et al, 2011), which is what we did during this phase. However, from

the moment we are able to get a couple of camera traps, we would like to use photo-trapping for our

mammal study. The method is especially efficient for inventories of cryptic animals as well as for

population studies of species for which individuals can be individually recognized by marks (Karanth,

1995; Carbone, 2001). Camera-trapping is an important non-invasive tool for assessing patterns of

mammal abundance and richness throughout space and time, and their link with activity patterns,

habitat use and reproductive information, which are key elements for wildlife conservation research.

Track surveys are efficient and usually involve low costs, but depend on suitable field conditions and

trained personnel (Burnham et al., 1980; Smallwood and Fitzhugh, 1995). Camera-trapping on the

other hand is more costly at the beginning, but is not so dependent on the environment to be

sampled, constant assistance or experienced field staff (Rappole et al., 1985). Once we have our

camera traps, we can combine the data from our track studies with the data from the photo-

trapping.


32

3.2.4 Turtle predation study along Carate and Leona beach, Osa Peninsula.

Introduction

Sea turtles have been swimming in our oceans for millions of years and are a fundamental link in

marine ecosystems by maintaining the health of coral reefs and sea grass beds. They survived

different environmental changes thanks to their special adaptations (Spotilla, 2011). Nowadays, sea

turtles face a whole new range of, basically human-induced, threats including poaching, climate

change, pollution, beach development and artificial lighting (Safina, 2006; Spotilla, 2011), highly

affecting their growth, reproduction and thus survival (Spotilla, 2011). Their temperature-dependent

sex determination makes them an excellent indicator species for climate change, and therefore a

flagship species for conservation. Increasing temperatures create a sex bias skewed towards females,

which can cause entire populations to collapse (Hamann et al., 2007; Valverde et al., 2010; Hawkes et

al., 2011). Their late maturation in conjunction with these anthropogenic threats make turtle

populations highly vulnerable and often unstable (Govan, 1998). A global rise in sea levels causes a

decline in nesting habitat, and changing ocean currents and sea temperature rises lead to decreasing

prey species availability (Fish et al., 2005; Chaloupka et al., 2008; Robinson et al., 2009). Worldwide,

six of the seven sea turtle species are now endangered and threatened with extinction (IUCN, 2016).

Predation, especially on the eggs and hatchlings, highly affects sea turtle populations in a negative

way. Natural predators such as crabs, raccoons, birds, coyotes and sharks play a major role in the

food web. Besides them, also humans are negatively affecting sea turtles by disturbing the nesting

beaches in different ways. People leaving trash near the shore for example, unintentionally invite

other, non-native species to look for food. Furthermore, in Central America, many communities

permit their domesticated dogs and cats to run free in coastal villages, leading to several sea turtle

nests being dug up and females being attacked while nesting. Furthermore, poaching and the illegal

trade of eggs, hatchlings and turtles further reduces the turtle populations. With as few as one in

1000 eggs reaching adulthood, the destruction of only a few nests can have a devastating effect on

any sea turtle population. The main problem is that, sea turtles have developed special adaptations

that allow them to live actively in the water, leaving them very clumsy on the land. They are not fast

enough to escape since they are unable to retract their heads and flippers into their shell, like land

tortoises, making them very vulnerable to these invasive predators (Sea Turtle Conservancy, 2016;

IUCN, 2008).

A number of conservation strategies have been established throughout Costa Rica, including limited

legal commercial egg harvesting on a nesting beach in Ostional during the first 36 hours of wet

season arribadas (mass arrival of turtles) (Campbell, 1998) and an annual catch of 1,800 black turtles


33

being granted to fishermen in Limόn (Troëng and Rankin, 2004). The latter may have increased

extractive use along with illegal hunting in the mid-90s, the ban on black turtle fishing and increased

law enforcement since 1999 may have increased female turtle survivorship (Troëng and Rankin,

2004). In other regions such as Tortuguero, the Costa Rican government has made egg poaching

illegal, in addition to prohibiting the trade of calipee, the edible part of the shell (Government of

Costa Rica 1963 and 1969; Troëng and Rankin, 2004). Meanwhile, the growing ecotourism industry in

Costa Rica has provided locals with an alternative source of income and has promoted conservation

throughout the country. To evaluate the effectiveness of such strategies, it is imperative that

monitoring programmes are long term as it can take decades for species with late maturity to show a

population response (Troëng and Rankin 2004; Bjorndal et al., 1999).

Costa Rica is an important nesting area for four sea turtle species: green turtles (Chelonia mydas),

hawksbills (Eretmochelys imbricata), olive ridleys (Lepidochelys olivacea) and leatherbacks

(Dermochelys coriacea) (Drake 1993). All four species have been recorded as nesting in southern

Costa Rica, on the Osa peninsula. Hawksbills and leatherbacks are listed as Critically Endangered,

green turtles are Endangered, and olive ridleys are Vulnerable (IUCN 2013). On the Osa Peninsula,

turtles are threatened primarily from predation by dogs, coastal development, illegal trade of eggs

and, to a lesser extent, turtle meat (Drake, 1996). Therefore, the aim of this project is to monitor the

frequency of predation and the health of the nesting turtle populations. The Frontier Costa Rica

Forest research programme works in partnership with CORTORCO, protecting the four species which

nest here (see above). The hawksbills and leatherbacks rarely nest on these two beaches whereas

the olive ridley is most commonly found nesting here (Troëng and Rankin 2004; Honarvar et al.,

2008; IUCN, 2013).


During this first phase of 2016 (January-March), we focused on the two common sea turtle species

present in this area; the Pacific green turtle (Chelonia mydas) and the olive ridley sea turtle

(Lepidochelys olivacea). The Pacific green turtle has a circumglobal distribution, occurring in tropical

and subtropical waters; they are migratory species and undertake complex movements and

migrations through geographically different habitats. Nesting takes place in more than 80 countries

worldwide (Hirth, 1997). Their movements within the marine environment are less understood, but

apparently they inhabit coastal water of over 140 countries (Groombridge & Luxmoore, 1989). The

Olive ridley sea turtle has circumtropical distribution, with nesting occurring in tropical waters and

migratory circuits in tropical and subtropical areas (Pritchard, 1969). They nest along the beaches of

nearly 60 different countries.


34

Both night and morning patrols were carried out on the beaches Playa Carate and Playa Leona.

Morning patrols began at 05:30 am on Playa Carate and 05:15 am on Playa Leona to minimise

surveyor exposure to direct sunlight and high temperatures. Night patrols typically started at 19:30

pm on both beaches. Each week, the high tide times were checked online in order to fit the morning

and night patrols into the schedule. To minimise the disturbance to nesting females, surveyors were

using red lights during night patrols and survey teams are limited to six people. The survey area for

both beaches is divided into 100 m sectors and each sector has his own number; with a 2.3 km

stretch of Playa Carate and a 2.5 km stretch of Playa Leona. For every turtle track encountered, the

following data had to be collected during the night patrols:

- Patrol date and names of recorders; this is for having an idea of the survey effort

- Time of recording; both start and end time of the survey, as well as the time when a nest is

encountered

- Beach sector number; always taking the smallest number (e.g. if observers are in between

sector 11 and 12, they will write down sector 11)

- Nest distance to the vegetation; with zone 1 (tidal inundation zone), 2 (beach area) or 3

(vegetation area)

- Sea turtle species; olive ridley turtle or Pacific green turtle

- Nest type associated with the tracks: Nest or False nest (N/F); false nest when the turtle

returned to the sea without nesting

- Track symmetry: symmetrical S or asymmetrical A

After writing down the data, the track was crossed through in the sand to avoid the track being

recorded again in subsequent patrols. The track characteristics were used to identify the species if

the turtles were absent, where asymmetrical tracks suggest Olive ridley and symmetrical tracks

suggest Pacific green. In-situ nests were confirmed by inserting a stick into the sand to locate the egg

chamber (indicated by a marked change in resistance when pressure applied) followed by careful

digging to confirm the presence of eggs. A false crawl was defined by the absence of a nest or where

it was clear that the turtle returned to sea without digging a nest.

During the morning patrols, predation of the nests was also checked. In the case of a predated nest,

obvious by the presence of predator tracks, egg shells and signs that the nest had been dug up, the

following was written down:

- Patrol date and names of recorders, this is again for having an idea of the survey effort

- Time of recording, both start and end time of survey, as well as the time when a nest is

encountered

- Beach sector number, always taking the smallest number


35

- Nest distance to the vegetation: zone 1 (tidal inundation zone), 2 (beach area) or 3

(vegetation area)

- Sea turtle species: olive ridley turtle or pacific green turtle

- Nest type associated with the tracks: Nest or False nest (N/F); false nest when the turtle

returned to the sea without nesting

- Measurement of the length of the tracks (edge to edge) at three different places and taking

the average

- Track symmetry: symmetrical S or asymmetrical A

- New or old nest (N/O); if old not re-recording, only if it is predated

- Predated nest (yes/no)

- Presence of tracks (yes/no); if possible identifying the predator based on the tracks

- Percentage of predation

An important note to make, is that every predated nest seen had to be analysed well to be sure that

it is a newly recording predated nest by checking if the eggs are still soft, meaning that the eggs are

recently predated. If a new predated nest is found, dig up the pieces of eggs and try to put them

together to determine the amount of eggs predated.

If nests are found around the lagoon, or the area in front of the airstrip until the coconut bar, we are

relocating the nests.

Results

In progress. During this first phase (January-March), we carried out basic turtle patrols on the

beaches of Carate and Leona. We still have to set up a clear standard protocol together with MINAE

and CORTORCO in order to understand what the main goals are regarding the sea turtle study.

During the upcoming weeks we are going to carry out more morning turtle patrols, depending on the

amount of volunteers present. For now, the point of conducting morning patrols is to check for the

amount of predation and to generally know how much nests were made and by which turtle species.

From June onwards, high turtle season begins, in which we will start to tag nesting turtles and do a

general health check. This will be explained in more detail in the next science report, in which the

collaboration with CORTORCO will be more explained. Furthermore, the data will be analysed

together with CORTORCO and will be reported directly towards MINAE.

Discussion

In progress.


36

3.2.5 Birds of Carate lagoon, a study on the species richness and abundance

Introduction

Coastal areas are typically characterised by a high human population density and thus activity,

causing a high pressure on the associated ecosystems, such as lagoons. Increasing human activity

results in environmental deterioration and disturbs biogeochemical processes that are going on in

the lagoons (Seitzing et al., 2005; Halpern et al., 2008; Qu & Kroeze, 2010). Due to ideal

temperatures and precipitation patterns, tropical coastal areas are very productive zones, and are

therefore highly affected by anthropogenic nutrient loading compared to similar habitats at higher

latitudes (Yule et al., 2010; Smith et al., 2012).

Coastal lagoons are shallow waterbodies, spatially separated from the ocean by sandbars and barrier

islands, or temporary separated during certain times of the year (Johnston, 2000). They are highly

productive ecosystems, providing several ecosystem services valuable for society, including fisheries,

storm protection, tourism, etc. (Gönenc & Wolflin, 2005; Anthony et al., 2009). Although, little

changes in water quality can have big effects on the functioning of the lagoon, and all its associated

living organisms. The degree to which a lagoon is sensitive towards changes in water quality mainly

depends on the lagoon type, referring to its exchange rate with the ocean and its size, and on the

faunal and floral communities present in and around the lagoon (Johnston, 2000). Due to the little

amount of information available about the sensitivity of lagoons towards changes in water quality,

there is a need to examine which environmental parameters affect the health of the lagoon in

general, with focus on the bird communities. There are a couple of quality parameters that are

expected to have a big influence on the functioning of lagoons, such nutrient enrichment, turbidity,

toxic contamination and organic enrichment (Johnston, 2000). Especially with changing climate,

these parameters can vary, affecting the physical structure, ecological characteristics and social

values associated with lagoons. Expected shifts in physical and ecological features range from

changes in flushing regimes, freshwater inputs, water chemistry to inundation and habitat loss

(Anthony et al., 2009). Gathering more information about coastal lagoons, especially in the context

of climate change, is critical. In this study, the bird species richness associated with a tropical lagoon,

situated in Carate, Osa Peninsula, Costa Rica, is studied; as well as their response upon changes in

environmental parameters. In addition, evidence from the few lagoon-specific studies undertaken, it

is suggested that once impacted (particularly by nutrient enrichment) lagoons may recover slower

from impacts due to changes in water quality. This highlights the need to identify water quality

impacts within lagoons as early as possible and suggests the need for a precautionary approach to

interpreting and acting on information that may indicate an impact (Johnston, 2000).


37

In this study, we want to examine the health of the lagoon Peje Perro in Carate. By surveying the bird

species richness and abundance, we can have an idea about the functioning of the lagoon.

Furthermore, we want to gain more information about different environmental parameters, their

change over time and the effect on the bird diversity.

Material and methods

The study is carried out at the coastal lagoon Peje Perro, located on Carate beach, Carate, Osa

Peninsula, Costa Rica (Figure ). During dry season (December-may), the lagoon is separated from the

Pacific ocean, changing the internal characteristics (e.g. salinity, nutrient concentration, turbidity).

Heavy rains allow the lagoon to connect again with the ocean. The lagoon is surrounded by lowland

rainforest and gets is disturbed by activities of local fisherman and tourists staying at the surrounding

ecolodges. A group of minimum three and maximum five observers are carrying out the survey at

two different spots close to the lagoon. Minimum three persons are necessary to fulfil the health and

safety requirements of Frontier Costa Rica Project (see earlier), and a maximum of five persons

allowed us to minimize the disturbance on the foraging behaviour of the birds during the survey. The

spots were chosen in such a way that we are close enough to see and identify the birds without

disturbing them too much. Once arrived at the survey point, all the different bird species present in

the lagoon, on the sandbanks as well as in the vegetation surrounding the lagoon were noted down.

We did not include the bird species present in the lowland rainforest starting right behind the lagoon

since these bird species are more likely to be part of the forest ecosystem. Using binoculars and the

bird identification books (Garrigues, 2014), we identified all the seen species during the survey. If we

were not able to identify them, pictures were taken and identified back on camp.


38

Results

During this first phase of the year, we were able to identify 29 different lagoon bird species present

in and around the lagoon of Carate. Table … gives an overview of the found species, saying which

species we found in the morning, afternoon or both.

Figure …

0

5

10

15

20

25

30

35

0 2 4 6 8 10 12 14

Nu

mb

er o

f sp

ecie

s

Cumulative sample (survey) number

Rarefaction curve Lagoon birds

Afternoon

Morning

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

0.800

0.900

SIMPSON EVENESS

Axi

s Ti

tle

Simpsons index and Eveness

morning

afternoon


39

According to the above graphs, the ACE and CHAO1, which represents the species richness of the

lagoon birds is higher during the afternoon then the morning. If we then have a look at the Simpsons’

index and Evenness, we see that the morning surveys show a higher species diversity. This means,

that if we take into account the abundance within each species observed, the species diversity is

higher in the morning; so basically it means that during the afternoons there are a slightly more

species found, but in lower amounts so they do not

0

5

10

15

20

25

30

ACE CHAO1

Axi

s Ti

tle

ACE and CHAO1

morning

afternoon


40

Figure … Comparing the amount of individuals within each species between morning and afternoon surveys.

0

20

40

60

80

100

120

Ab

solu

te a

mo

un

t o

f se

ein

gs

Lagoon bird species

Lagoon bird species comparison morning / afternoon

MORNING AFTERNOON


41

From the above curves we can see that we didn’t reach the maximum amount of species present in

the area yet. This is because the curve does not really levels off at the end. With the equation we

could estimate how many surveys we need to level off the curve, so to see when we reach the

maximum amount of species. However, since we do not yet see a level off, the equation is not totally

correct and we need more samples (surveys) in order to make a more representative equation.

The Simpson’s mean (D) is 6.6, and from this we can calculate the Simpson’s mean index (1-D) with

the formula 1-D = 1-(1/D). The result is 0.848485. Since this is close to 1, it means we have a high bird

species richness over the surveys. Using the Simpson’s diversity index, we can measure the evenness

(E) with the formula E = (1/D)/S, with S the amount of samples (surveys). The result is 0.55.

32,33 0 47,27 0 28,49 Respectively ACE, ICE and CHAO1

Discussion

We compared the Lagoon bird species richness between morning and afternoon surveys and found …

If we combined all the data (morning and afternoon data) all together, we found…

From these results we can say that…

Furthermore, it should be mentioned that this is the first time we carry out a lagoon bird study.

During the first weeks, observers had to get to know the birds and needed more time to identify

them. Now, we are more skilled and are able to spot and identify the different bird species more

easily.

During the next phase we would like to add how disturbance have an effect on the species richness

and abundance of the lagoon birds. By comparing surveys with (human) disturbance to surveys

without (human) disturbance, we can see if by kayaks, fisherman, etc. have a negative influence on

the bird diversity in the lagoon. It could be noted that we, as observers, also disturb the birds present

in and around the lagoon. However, since we see a high species richness, we can say that our

presence has none or very low effect on their behaviour.

Another idea is to include different environmental parameters into the study. Since it is known that

salinity, temperature, pH, depth, etc. influence the functioning of lagoon ecosystems, it is important

to know have they vary over time and if this influences the presence of bird species in and around

the lagoon. In order to carry out this extra measurements, we need to contact MINAE and follow the

standard protocol for water quality monitoring.

Finally, we would like to use kayaks during the next phase in order to get around the whole lagoon.

We will go into the water before sunrise and found fixed spot in the lagoon and wait until birds

arrive. In this way, we don’t disturb them since we are not moving in the kayak.


42


43

3.2.6 Bird species richness and abundance in primary, secondary and degraded forest

Introduction

The highly heterogeneous environments of Costa Rica give rise to many species-rich communities;

particularly those within the bird families (Herzog, Kessler & Cahill, 2002). Costa Rica hosts

approximately 850 bird species, of which 160 species are endemic to country (Henderson, 2010). This

high bird species richness means that Costa Rica has a relatively long history of studies focusing on

bird community structure (e.g., Young et al, 1998; Blake & Loiselle, 2001; Sigel et al, 2006) and

demography (e.g., Ruiz-Gutiérrez et al, 2008; Young et al, 2008; Woltmann & Sherry, 2011). Birds

provide various important ecological functions, such as seed dispersion and pollination, and can

therefore help in the maintenance of plant communities, and even contribute towards the

reforestation of fragmented habitats (Pejchar et al. ,2008). However, the majority of bird studies

have been carried out in pristine habitats with very little attention given to degraded or fragmented

areas (Wilson, Collister & Wilson, 2011). Furthermore, partly due to its remoteness, little is known

about the bird communities of the Osa Peninsula despite its extraordinary species diversity and high

levels of endemism (Wilson, Collister & Wilson, 2011).

Home to approximately 375 species of birds (or 420 species according to Garrigues, 2007), including

many migratory birds and 18 endemic species (Sanchez-Azofeifa et al, 2002), the Osa Peninsula

comprises one of the largest remaining tracts of intact lowland rainforest in Mesoamerica (Barrantes

et al, 1999). This provides important habitat for a myriad of bird species. While 39% of the region is

under the protection of Corcovado National Park, in recent decades significant development,

deforestation and forest fragmentation has occurred outside of the reserve (Sanchez-Azofeifa et al,

2002).

Deforestation and fragmentation is considered the primary threat to birds in the Osa Peninsula (Osa

Conservation, 2016). Due to a human population growth rate of 2.6% (Sánchez-Azofeifa et al, 2001)

and increases in ecotourism, large areas of forest have been cleared to make space for agricultural

practices and the hospitality industry (Minca & Linda, 2002). Studies have found that in the period

between 1979 and 1997 the percentage of forested area in the Osa decreased from 97% to 89%

(Sanchez-Azofeifa et al, 2002). Furthermore, Sanchez-Azofeifa et al (2002) found that as of 1997, the

majority of the remaining forest outside of Corcovado National Park has been altered, with only 44%

of the region representing mature forest. Today, the tropical forest exists as a patchwork of various

size, age and connectivity within a human-dominated landscape (Wilson, Collister & Wilson, 2002).


44

Particular bird groups, such as understory insectivores (Canaday, 1996; Sekercioglu et al, 2002; Sigel

et al, 2006), can be very sensitive to such changes whilst others are able to utilise degraded and

fragmented habitats (Wilson, Collister & Wilson, 2002). Development is likely to continue in the Osa

Peninsula and thus it is of the utmost importance to understand how birds, outside of Corcovado

National Park, are being affected by these changes.

In addition to deforestation and fragmentation the birds of the Osa Peninsula are up against another

threat: climate change. This threat is not unique to the region, however, changes in temperature,

precipitation and greater climatic extremes are likely to have significant impacts on the avifauna. Due

to the fact that birds are endothermic, increased temperatures may cause greater energy use for

thermoregulation (Wormworth & Mallon, 2006). Additionally, temperature changes can indirectly

affect the birds reproduction, timing of breeding and migration (Wormworth & Mallon, 2006). For

example, shifts in temperatures cause birds to shift the timing of seasonal events such as egg laying

or migration (Wormworth & Mallon, 2006). This causes birds to be out of synchrony with other

species, particularly plants and insects, which are necessary for their survival (Wormworth & Mallon,

2006). Such changes may significantly impact species’ reproductive success which could ultimately

result in the collapse of breeding populations in the long-run (Wormworth & Mallon, 2006).

Precipitation changes are also expected to negatively affect bird populations. Studies have shown

that periods of low or zero rainfall are correlated with lower bird populations due to reduced food

availability (Wormworth & Mallon, 2006). Furthermore, it is believed that climate change is likely to

increase extreme weather events such as drought or flooding (Wormworth & Mallon, 2006). Extreme

conditions can alter important habitats and reduce the survival rates of both young and adult birds.

Moreover, drought or floods in critical stopover areas along bird migration routes can impair

migratory birds’ ability to reach their final destination (Wormworth & Mallon, 2006). Altogether, the

effects of climate change and birds responses to it will vary from species to species, thus it is critical

that the different species of the Osa Peninsula are monitored in order to determine how they are

being affected.

Overall, the high species diversity and endemism of the avifauna in the Osa Peninsula coupled with

the threats of deforestation, fragmentation and climate change, highlights the need to better

understand and monitor the birds in the region. Due to the lack of scientific studies on birds in the

Osa Peninsula, Frontier aims to determine the species richness and abundance of birds in Carate in

relation to their habitat and disturbance since bird distribution and species richness is often

explained by habitat type and environmental characteristics. Therefore, thanks to their sensitivity

towards environmental changes, birds are good indicators of habitat health (Wilme & Goodman,


45

2003). Monitoring trends in bird diversity may help to identify species at risk of population decline or

even extinction due to human-induced environmental changes, such as habitat fragmentation and

loss, climate change, pollution and pet trade (Pejchar et al., 2008).

As such, the main objective is to compare the species richness and abundance between disturbed,

secondary and primary forest habitats through point count surveys whereby the bird species are

recognized by sound and sight. In addition, Frontier aims to support the goals of the National Parks

Service in the United States of America and MINAE by monitoring migratory birds species that inhabit

both North America and migrate to Costa Rica during winter periods. Finally, due to the sensitivity of

birds to climate change, Frontier aims to monitor the bird species diversity and abundance in

conjunction with climatic changes over the long term.


This study focuses on 44 bird species, and the species are selected based on the following criteria;

endemic species, data deficient/poorly studied species, specialist species, migratory species, species

under threat (according to the IUCN) and species that perform a high ecological function. Worldwide,

the most important places for habitat-based conservation of birds are the Endemic Bird Areas (EBAs).

Most of the bird species are widespread and can inhabit large ranges of habitats. Some however are

said to be endemic since they are restricted to specific areas due to food and habitat requirements.

The landscapes where these species occur are high priority for broad-scale ecosystem conservation.

EBA’s are found around the world, but most of them are located in the tropics and subtropics,

especially the tropical lowland forest and moist montane forest. Geographically, EBA’s are often

islands or mountain ranges (Birdlife International, 2008). The poorly studied species are species with

very few or deficient data available about their status, distribution, abundance, etc., which makes

them highly prioritized species to study. Specialist species are occurring in certain habitats because of

specialist habitat or food resource needs. If their habitat disappears, it is very likely that the species

disappears will disappears too. Regarding the migratory species, we are working together with the

American National Park of North America and Canada. The bird species that are migrating from north

to south during northern hemisphere winters are being studied since little information is available

about these species when they are moving towards the south. Finally, the bird species with

important ecological functions are also our focus on species, since they have important functions

within the ecosystem they live. For example, woodpeckers make holes in trees that are habitats for

other species such as bats, beetles, etc.


46

Table …: Overview of the selected 44 bird species on study.

Bird species common name Bird species Latin name Selected criteria

Fiery-billed Aracari Pteroglossus frantzii Endemic species to Pacific Costa Rica

and Western Panama

Chestnut-mandibled Toucan Ramphastos swainsonii Vulnerable

Black-bellied Wren Pheugopedius fasciatoventris Endemic species to Pacific Costa Rica

and Western Panama

Riverside Wren Cantorchilus semibadius Endemic species to Pacific Costa Rica

and Western Panama; Data deficient

Cherries Tanager Ramphocelus costaricensis Endemic species to Pacific Costa Rica

and Western Panama; Data deficient

Blue-crowned Manakin Lepidothrix coronata Endemic species to Pacific Costa Rica

and Western Panama

Red-capped Manakin Ceratopipra mentalis

Orange-collared Manakin Manacus aurantiacus Endemic species to Pacific Costa Rica

and Western Panama

Pale-billed Woodpecker Campephilus guatemalensis Specialist species; Ecologically

important function

Golden-naped Woodpecker Melanerpes chrysauchen Endemic species to Pacific Costa Rica

and Western Panama

Long-tailed Woodcreeper Deconychura longicauda Near threatened

Bright-rumped Atilla Attila spadiceus Disturbance indicator

Rufous Mourner Rhytipterna holerythra

Rufous Piha Lipaugus unirufus Specialist species

Tawny-Crowned Greenlet Hylophilus ochraceiceps Specialist species; Data deficient

Scarlet Macaw Ara macao Data deficient

Turquoise Cotinga Cotinga ridgwayi Endemic species to Pacific Costa Rica

and Western Panama; Vulnerable

Yellow Warbler Setophaga petechia Migratory species

Golden-winged Warbler Vermivora chrysoptera Migratory species

Blue-winged Warbler Vermivora cyanoptera Migratory species

Black-hooded Antshrike Thamnophilus bridgesi Endemic speices to Pacific Costa Rica

and Western Panama; No data

Black-cheeked Ant-tanager Habia atrimaxillaris Endemic species to the Osa Peninsula;

Endangered

Bicoloured Ant-bird Gymnopithys leucaspis

Dot-winged Antwren Microrhopias quixensis Specialist species

Ruddy-tailed Flycatcher Terenotriccus erythrurus Specialist species

Sulphur-rumped Flycatcher Myiobius sulphureipygius

Yellow-billed Cotinga Carpodectes antoniae Endemic to Costa Rica; Endangered

Baltimore Oriole Icterus galbula Migratory species


47

Rufous-tailed Jacamar Galbula ruficauda Disturbance indicator

Wood Thrush Hylocichla mustelina Near threatened; Migratory species

Smooth-billed Ani Crotophaga ani Disturbance indicator

Common Potoo Nyctibius griseus Poor data; Vulnerable

Great Tinamou Tinamus major Poor data; Climate change indicator

Great Curassow Crax rubra Vulnerable; Climate change indicator

Spectacled Owl Pulsatrix perspicillata Ecologically important function

Crested Guan Penelope purpurascens Poor data

Marbled wood Quail Odontophorus gujanensis Near Threatened

Spot-crowned Euphonia Euphonia imitans Endemic species to Pacific Costa Rica

and Western Panama; Specialist

species

Green-shrike Vireo Vireolanius pulchellus Data deficient

Mealy Parrot Amazona farinosa Ecologically important function

White-crowned Parrot Pionus senilis Poor data; Ecologically important

function

Brown-hooded Parrot Pyrilia haematotis Poor data; Specialist species

Black-Throated Trogon Trogon rufus Poor data

Baird’s Trogan Trogon bairdii Endemic species to Costa Rica; Near

Threatened

Using point counts, estimates of the bird species richness and abundance can be made. Point counts

are a widely used method to assess the distribution patterns and relative abundance of birds in

tropical habitats (Miller et al., 1998; Sánchez-Azofeifa et al., 2001; Henderson, 2010). A point count

refers to a count carried out by someone that is standing at a fixed place, from which the target

species (birds) are counted by sight and call, and this for a fixed period of time (Bibby et al., 2000;

Gibbons & Gregory, 2006; Hartley & Greene, 2012). The methodology is quite straightforward and

observers can easily gather the required data by walking a trail and stop at different points to record

all the present bird species by sound and sight. It must be said that, due to the high level of tree

density within a tropical forest as well as the very high species diversity in this region, there is quite a

high level of experience necessary to detect and identify birds accurate. The point counts are carried

out along all the different trails; Luna ridge, Leona ridge, Shady lane, Beach trail, Rio Carate, Attalea

loop, road. During each survey, three point counts are carried out, separated 250 m from each other

and started at 100 m from the forest edge. Since we work with a distance radius of 0 – 30 m (1), 30 –

100 m (2) and >100 m (3), it is important to stick with the 250 m in between the point counts to avoid

an overlap of counts. Furthermore, it is important to take into account the effort efficiency of the

observers. This is why we chose to do not more than three point counts during every survey since

there is a drop in focus over time, making it important to find a compromise between collection


48

effort and precision / accuracy (Verner, 1985). Before starting the recording period of ten minutes,

there is a two minute settling period to allow the birds coming back after our disturbance from

walking towards the point counts. The point counts are permanent points, which are permanently

chosen locations within a site and clearly marked with colourful tape flags (Huff et al., 2000). All the

birds that are seen and heard within the different radius are noted down (sight: S; sound: H), as well

as the flying-over and flying-thrus birds are recorded in a separate list as respectively FO and FT.

Figure …: Graphic view of the distance radius used during the point counts.

Results

In progress. So far, only pilot studies have been carried out since all the staff members as well as the

volunteers are still in the process of learning the bird calls and recognizing them by sound and sight.

Furthermore, we will start to use bird sound recording equipment in order to record the bird calls in

the field and identify them back on camp by using the online catalogued bird calls. In this way we will

have a more reliable dataset by double checking our bird call recognizing skills in the field with the

recordings. Furthermore, we can analyse how are skills are improving over time by correlating our

field notes with the recordings checked on camp.

Discussion

In progress.

1 3 2


49

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Blake, J. G., & B. A. Loiselle. 2001. Bird assemblages in second-growth and old-

growth forests, Costa Rica: Perspectives from mist-nets and point counts. The Auk.

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Canaday, C. 1996. Loss of insectivorous birds along a gradient of human impact in

Amazonia. Biological Conservation. 77: 63–77.

Herzog, S.K., Kessler, M., & Cahill, T.M. 2002. Estimating species richness of tropical

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environmental management. Oxon: CABI Publishing, UK. 103-127.

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