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Comparative diet analysis of the eurasian otter
(Lutra lutra, Linnaeus, 1758) in two different habitats: Putna - Vrancea Natural Park and Lower Siret Valley
Natura 2000 Site, Romania
PHD. STUDENT BOUROȘ GEORGE
“
”
There are no prizes for
answering: otters eat fish.
Paul Chanin, 2013
What else do they eat?
Does the diet vary during the year?
Introduction The Eurasian otter is an endangered semi-aquatic carnivore belonging to the
Mustelidae family and is protected by international legislation;
Lutra lutra is classified as ‘Near Threatened’ by the IUCN and considered‚vulnerable’ by the Romanian Vertebrate Red Book.
The diet of the otter in Romania is poorly known.
The otter is one of only a few European carnivores that has developed the ability toactively forage both in water and on land.
The Eurasian otter uses as habitat a wide range of ecosystems: highland andlowland lakes, rivers and streams, as well marshes, riparian forests, delta and costalareas. All this habitats determine a high variability of the food items that composethe otter’s diet.
The purpose of this work is to compare the otter’s diet composition in two different study areas of SE Romania, describing possible differences through seasonal diet composition.
Study areaThe Natural Park is located in SE Romania, NE of Vrancea County andcovers an area of 382.13 km², with altitude ranging from 435 m in thevalley of the Putna River to over 1785 m in Goru Peak.
Putna River collects all the streams in the park and forms a narrow west- east oriented valley in the central part of the park. Most of the flowtakes place at the end of the spring (44%) and early summer (30%).
The Natura 2000 SCI and SPA Lower Siret Valley is located in the north-eastern part of the Romanian Plain, along the riverbed of the Siretriver, in its sector between cities Adjud and Galati.
The area of SCI is 250.81km² and of SPA is 364.92km² with an altituderanging from 0 to 302 m.
The site is dominated by a vegetation characteristic to the riparianmixed forests, strongly influenced by the existence of some branchesof Putna and Siret rivers.
Lepsa river
Siret river
Materials & Methods
174 otter spraints were collected from December
2012 to July 2014 from Putna-Vrancea Natural Park
(n=118 samples) and Lower Siret Valley Natura 2000
Site (n=56 samples);
For any spraint were noted following information:
date, time, observer, geographic coordinates, river
or stream name, site code and estimated spraint
age;
Spraints were collected all year round, in order to
notice variations in the trophic resource utilization by
season;
Materials & MethodsSpraints were individually soaked in a metal container containing one third water and twothirds detergent for 3 days to a week;
Samples were washed by tipping the contents of the cup into a 0.5 mm fine mesh sieve;
The spraint particles were then carefully removed from the sieve and placed in a whiteplastic tray;
Using different size forceps and needles, any bone fragments were identified, picked out andsorted into groups.
The largest vertebra and exoskeletons could be identified with the naked eye, but for thesmallest was used a magnifier and a microscope (10 X).
Soricinae jaw Cyprinidae jaw Insectivora paw Fish eye
The percentage of occurrence of each prey group was plotted per spraint using a comparison
chart for estimating percentage composition.
Also it was calculated the relative frequency of occurrence (RFO) per prey item and
percentage frequency of occurrence (PFO) using the following formulas:
RFO % = Number of occurrences of a prey group x 100/Sum of occurrences of all prey groups
PFO % = Number of spraints containing a particular prey group x 100/ Total number of spraints in
sample
After being analyzed, feces were dried and stored in a collection in plastic tubes which has
been assigned a code and date;
Materials & Methods
Salmonidae jaw Natrix vertebrae Feathers Crayfish eggs
Results & Discussion
22,476 %
56,088 %
17,724 %
1,756 %
0,027 %
2,169 %
0,261 %
Amphibia
Pisces
Mammalia
Insecta
Gastropoda
Reptilia
Plantae
PERCENTAGE OF OCCURRENCE
Based on comparison chart for estimating spraint percentage composition.
2,839 %
36,665 %
12,143 %
0,417 %
0,017 %
0,089 %
1,100 %
14,135 %
32,590 %
Amphibia
Pisces
Mammalia
Insecta
Gastropoda
Reptilia
Plantae
Aves
Crustaceea
Putna Vrancea Natural Park Lower Siret Valley
Results & Discussion
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Putna Vrancea Natural Park
Amphibia Pisces Mammalia Insecta Gastropoda Reptilia Plantae
PERCENTAGE OF OCCURRENCE plotted per spraint
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Exc
rem
en
t 1
Exc
rem
en
t 2
Exc
rem
en
t 3
Exc
rem
en
t 4
Exc
rem
en
t 5
Exc
rem
en
t 6
Exc
rem
en
t 7
Exc
rem
en
t 8
Exc
rem
en
t 9
Exc
rem
en
t 1
0
Exc
rem
en
t 1
1
Exc
rem
en
t 1
2
Exc
rem
en
t 1
3
Exc
rem
en
t 1
4
Exc
rem
en
t 1
5
Exc
rem
en
t 1
6
Exc
rem
en
t 1
7
Exc
rem
en
t 1
8
Exc
rem
en
t 1
9
Exc
rem
en
t 2
0
Exc
rem
en
t 2
1
Exc
rem
en
t 2
2
Exc
rem
en
t 2
3
Exc
rem
en
t 2
4
Exc
rem
en
t 2
5
Exc
rem
en
t 2
6
Exc
rem
en
t 2
7
Exc
rem
en
t 2
8
Exc
rem
en
t 2
9
Exc
rem
en
t 3
0
Exc
rem
en
t 3
1
Exc
rem
en
t 3
2
Exc
rem
en
t 3
3
Exc
rem
en
t 3
4
Exc
rem
en
t 3
5
Exc
rem
en
t 3
6
Exc
rem
en
t 3
7
Exc
rem
en
t 3
8
Exc
rem
en
t 3
9
Exc
rem
en
t 4
0
Exc
rem
en
t 4
1
Exc
rem
en
t 4
2
Exc
rem
en
t 4
3
Exc
rem
en
t 4
4
Exc
rem
en
t 4
5
Exc
rem
en
t 4
6
Exc
rem
en
t 4
7
Exc
rem
en
t 4
8
Exc
rem
en
t 4
9
Exc
rem
en
t 5
0
Exc
rem
en
t 5
1
Exc
rem
en
t 5
2
Exc
rem
en
t 5
3
Exc
rem
en
t 5
4
Exc
rem
en
t 5
5
Exc
rem
en
t 5
6
Lower Siret Valley
Amphibia Pisces Mammalia Insecta Gastropoda Reptilia Plantae Aves Crustaceea
Results & DiscussionPERCENTAGE OF OCCURRENCE plotted per spraint
Results & Discussion
24,9 %
34,8 %
15,2 %
18,6 %
1,6 %
1,6 %2,9 %
Amphibia
Pisces
Mammalia
Insecta
Gastropoda
Reptilia
Plantae
Relative Frequency of Occurrence (RFO)
Putna Vrancea Natural Park Lower Siret Valley
36,1 %
8,5 %
10,4 %
0,9 %
0,9 %
8,6 %
9,5 %
24,8%
5,7 %
Pisces
Mamalia
Insecta
Gastropoda
Reptilia
Plantae
Aves
Crustaceea
Amphibia
Results & Discussion
63,5 %
88,9 %
38,9 %
47,4 %
4,2 %
4,2 %
7,6 %
Putna Vrancea Natural Park
Amphibia
Pisces
Mammalia
Insecta
Gastropoda
Reptilia
Plantae
Percentage Frequency of Occurrence (RFO)
67,8 %
16,1 %
19,6 %
1,8 %
1,7 %
16,1 %
17,8 %
46,4 %
10,7 %
Lower Siret Valley
Pisces
Mamalia
Insecta
Gastropoda
Reptilia
Plantae
Aves
Crustaceea
Amphibia
Results & DiscussionThe seasonal variation of otter’s diet
Putna Vrancea Natural Park Lower Siret Valley
Results & DiscussionThe altitudinal variation of otter’s diet
In the Lower Siret Valley the difference in
altitude is not high so I could not identify a
correlation between altitude and
consumption of prey species.Putna Vrancea Natural Park
Conclusions
The dietary study reveals that fish (49,8 %), frog (16,1 %), mammals (15,9 %) and crayfish
(10,5 %) are the main food items consumed by otters, followed by: birds (4,5 %), reptiles
(1,5 %), insects (1,3 %), mollusks (0,02 %) and plants (0,5 %) showing a seasonal variability
in Putna Vrancea and Lower Siret Valley.
Otter can serve as flagship species to
raise awareness for conservation of
aquatic ecosystems in many areas by
its function of top predator.
Otters are widely distributed predators
in Romania and could be used as
“umbrella” species in every freshwater habitat, in order to ensure the
conservation of all prey species that compose its diet.
AcknowledgementsFor Support:
For advices & coordination:
m.c. Acad. Dr. Dumitru Murariu
Dr. Silviu Chiriac
For training:
...and many more
For help during field work:
Teodora Sin
Virginia García López
Francisco Parra Rodriguez
Manuel Menéndez Puertas
Rocío Hermosilla Garzón
Jesús Alberto Sánchez Pardo
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