RuahaPrReport 2013-03

AERIAL CENSUS OF LARGE ANIMALSIN THE

RUAHA-RUNGWA ECOSYSTEMDRY SEASON, 2013

POPULATION STATUS OF AFRICAN ELEPHANT

Conducted by

TANZANIA WILDLIFE RESEARCH INSTITUTEin collaboration with

TANZANIA NATIONAL PARKSWILDLIFE DIVISION

Commissioned by TANAPA through

UNDP SPANEST PROJECT

TAWIRI 2013 Ruaha- Rungwa

ii

Systematic Reconnaissance Flight (SRF) Census Report

Population Status of African Elephant in Ruaha – Rungwa Ecosystem, Dry Season, 2013

Cover photo: Elephant family

Tanzania Wildlife Research InstituteConservation Information and Monitoring Unit

PO Box 661Arusha, Tanzania

Tel: ++ 255 27 2507796Emails: [email protected]

[email protected]


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INTRODUCTION

Aerial survey was conducted in the Ruaha-Rungwa ecosystem during the dry season of 2013 (October 28th through November 7th, 2013). The census covered an area of 50,889 km2 comprising; Ruaha National Park, Rungwa Game Reserve, Muhesi Game Reserve, Kizigo Game Reserve, Itigi thickets and open area/village land outside protected areas (Figure 1).

Census objectives

The survey aimed at assessing the current population status of large mammals, identifying their diversity, distribution and determines population trends by comparing results with previous estimates.

This Preliminary Report focuses on the estimate of elephant population size in the ecosystem.

Previous censuses

Several systematic reconnaissance flight (SRF) surveys have been conducted in Ruaha-Rungwa ecosystem (Table 1).

METHODOLOGY

Census technique:

Aerial census was conducted using Systematic Reconnaissance Flight (SRF) technique. (Norton-Griffiths 1978)

Three aircrafts (Appendix 1) flew simultaneously at an average height of 350ft above ground and at an average speed of 180 km/h. A total of 119 transects were laid in North – South direction. Transects were spaced 5 km apart except for Itigi Thickets where transects were spaced 10 km apart (Figure 2 and 3). The total length of transects was 13,173 km.

Each transect was sub-divided into sub-units defined by geo-referenced points. Geo-referencing of aircraft on transect was determined by GPS, according to previously prepared geographical coordinates (latitude and longitude).

Data analysis

Population estimates were calculated using Jolly's Method 2 of Unequal Sized Units (Jolly 1969) and change in population size determined using d-test (Cochran 1954).


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Table 1. Wildlife Surveys in the Ruaha-Rungwa Ecosystem, 1965 – 2013 (NP = National Park, GRs=Game Reserves).

Year Season Surveyed areaArea

covered (km²)

Source

1965 Dry Ruaha NP (Rift Valley Stratum) 295 Savidge, 19681972 Dry Ruaha NP 10,200 Norton-Griffiths, 19751973 Wet Ruaha NP 10,200 Norton-Griffiths, 1975

1977 Dry Ruaha - Rungwa & Kizigo GRs 31, 500Barnes & Douglas-Hamilton, 1982

1990 Dry Ruaha NP, Rungwa & Kizigo GRs 26,763 TWCM, 19911993 Dry Ruaha NP, Rungwa, Kizigo & Muhesi GRs 41,297 TWCM,19941993 Wet Ruaha NP, Rungwa, Kizigo & Muhesi GRs 43,391 TWCM, 19941996 Wet Ruaha NP, Rungwa, Kizigo & Muhesi GRs 41,831 TWCM, 20001999 Dry Ruaha NP, Rungwa, Kizigo & Muhesi GRs 41,635 TWCM, 20001999 Wet Muhesi GR and surrounding area 4,545 TWCM, 20002002 Dry Ruaha NP, Rungwa, Kizigo & Muhesi GRs 36,063 TAWIRI, 20032006 Dry Ruaha NP, Rungwa, Kizigo & Muhesi GRs 43,601 TAWIRI, 20072009 Dry Ruaha NP, Rungwa, Kizigo & Muhesi GRs 43,641 TAWIRI, 20102011 Dry Ruaha NP, Rungwa, Kizigo & Muhesi GRs 43,763 TAWIRI, in progress2013 Dry Ruaha NP, Rungwa, Kizigo & Muhesi GRs 50,889 This report

Figure 1: The Ruaha - Rungwa ecosystem showing administrative areas.


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Figure 2. Planned transect for the Ruaha-Rungwa ecosystem aerial survey, dry season 2013.

RESULTS

The Ruaha-Rungwa survey was conducted successfully as parameters show in Table 2 and 3, and track log for SRF transects in Figure 3.


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Table 2. Parameters of the Ruaha-Rungwa ecosystem SRF census conducted between October 28 and November 7, 2013

AIRCRAFT 5H-CFA5H-TNP

5H-MPK COMBINED

Survey Area (km2) 28,152 10,025 12,712 59,889Total number of transects

60 29 30 119

Flying height (feet above ground level)Average 344 355 363 354

Mode 340 360 350 350Median 350 350 360 355

Standard deviation 86 75 74 152Minimum 70 280 300 70Maximum 3360 760 800 3,360

Total number of Sub-units

2,054 1,017 757 3,828

Transect Distance (km) 6,690 3,190 3,293 13,173Ground Speed (km/h) 175 182 183 180Sample Area (km2) 1637 570 744 2,951

Table 3. Sample Fraction (%) of the Ruaha-Rungwa census zone

SRF StratumSample fraction

5 km transect spacing 8.810 km transect spacing 2.2Total 11

Elephant population estimate

The elephant population size in Ruaha-Rungwa ecosystem was estimated to be 20,090 ± 3,282 SE (Table 4). The estimate was derived from 1,247 elephants counted along 119 transects.


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Table 4. Estimates of elephant population size shown by administrative areas

Administrative areaNumber counted

EstimateStandard

ErrorSurveyed

area (km2)

Ruaha National Park 531 8,804 2,401 19,555Rungwa Game Reserve 516 7,991 2,025 9,119Kizigo Game Reserve 108 1,767 952 4,990Muhesi Game Reserve 30 511 418 5,069Itigi thickets 6,075Outside Protected Areas 62 1,017 421 6,082Total 1,247 20,090 3,282 50,889

Figure 3. Track log of flown transects in the Ruaha-Rungwa SRF survey.


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Elephant distribution and density

The density of elephant was not uniform across the ecosystem. Relatively higher densities were found in small pockets in the north-west and central parts of the ecosystems (Figure 4).

Figure 4. Density and distribution of elephants in the Ruaha-Rungwa ecosystem as recorded during the 2013 dry season census.

Estimate of elephant carcasses

A total of 214 elephant carcasses were recorded in four classes based on age of the carcass since when the animal died (Table 5). The estimated number of elephant carcasses in the Ruaha-Rungwa census zone is 3,496 ± 342 SE; the time of death of


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the animals spans over a period of up to 10 years. Results indicate that relatively fewer animals were killed in the last twelve (12) months (<13%)

Table 5. Estimate of elephant carcasses for the census zone

Class Counted carcasses

Carcass estimate

Standard error

Age of carcass

(months)

EC1 7 114 48 < 1 mo

EC2 20 327 87 1 – 12

EC3 113 1,847 217 > 12

EC4 74 1,208 245 >30-120

Grand Total 214 3,496 342

Elephant carcass distribution and density

Elephant carcasses were widely distributed in the central part of the census zone (Figure 5). Higher carcass numbers were found in six isolated areas. However, more than 85% of sighted carcasses were estimated to be more that 18 months old.

Elephant carcass ratio

The carcass ratio for Ruaha-Rungwa ecosystem is 14.6%; calculated using counted numbers of live elephant (1,247) and skeletons (214). This carcass ratio indicates a population that is suffering unnaturally high mortality. A carcass ratio of about 7-8% is considered to represent natural mortality (Douglas-Hamilton and Burrill 1991).

Elephant population trend in Ruaha-Rungwa ecosystem (1976 to 2013).

The estimated population size of elephants (20,090 ± 3,282 SE) presents a significant decline from 31,625 ± 2,890 that was estimated in 2009 (d-test = 2.6, p>0.05) (Table 4, Figure 6).


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Figure 5. Density and distribution of elephant carcasses in the Ruaha-Rungwa ecosystem, dry season 2013.


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Table 4. A list of censuses conducted in the Ruaha-Rungwa ecosystem that are considered comparable (Note differences in size of census area).

Year Season Surveyed areaPopulation

EstimateStandard

Error

Area covered

(km²)Source

1977 Dry Ruaha - Rungwa & Kizigo GRs 31, 500Barnes & Douglas-Hamilton, 1982

1990 DryRuaha NP, Rungwa & Kizigo GRs

11,712 5,481 26,763 TWCM, 1991

1993 Dry Ruaha NP, Rungwa, Kizigo & Muhesi GRs

19,284 3,150 41,297 TWCM,1994

1996 WetRuaha NP, Rungwa, Kizigo & Muhesi GRs

13,225 2,126 41,831 TWCM, 2000

2002 DryRuaha NP, Rungwa, Kizigo & Muhesi GRs

24,993 3,027 36,063 TAWIRI, 2003


35,461 3,653 43,601 TAWIRI, 2007


31,625 2,890 43,641 TAWIRI, 2010

2013 DryRuaha NP, Rungwa, Kizigo & Muhesi GRs 20,090 3,282 50,976 This report

Figure 6. Elephant population trend in the Ruaha-Rungwa ecosystem 1988 -2013.

-

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

1988 1992 1996 2000 2004 2008 2012

Elep

hant

Pop

ulat

ion

size

Year


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Possible sources of bias

Undercounting elephants (i) missing animals hidden under thick vegetation cover, (ii) Undercounting elephant carcasses because of difficulties of detecting skeletons (i)

covered in its drying skin, (ii) discoloration for EC4, or (iii) hidden in vegetation Difficulty of estimating age of carcass which in-turn could be confounded by various

environmental factors.

CLASS MONTHS DESCRIPTIONCarcass 1 < 1 Fresh, still has flesh giving the body a rounded appearance. Vultures

probably present and ground still moist from body fluids.

Carcass 2 02 - 12 Recent (<1 year). Rot patch and skin still present. Skeleton not scattered.

Carcass 3 13 - 24 Old (>1 year). Clean bones, skin usually absent, vegetation re-grown in rot patch.

Carcass 4 > 24 Very old (up to 10 years). Bones scattered and turning grey.

Acknowledgements

We thank support from Wildlife Division, Tanzania National Parks. Logistics, SPANEST and Managements of Ruaha National, Rungwa, Kizigo &

Muhesi Game Reserves. Funding came from UNDP through TANAPA-SPANEST. Census and ground crew for dedication and hard work.


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BIBLIOGRAPHY

Cochran, W. G. (1954). "The combination of estimates from different experiments." Biometrics 10: 101-129.

Douglas-Hamilton, I. and A.K. Hilman. 1981. Elephant Carcasses and Skeletons as Indicators of Population Trends. In Low level Aerial Survey Techniques Workshop. International Livestock Centre for Africa, Monograph No. 4, Addis Ababa.

Jolly, G. M. (1969): "Sampling methods for aerial census of wildlife populations." East African Agriculture and Forestry Journal 34: 46-49.

Norton-Griffiths (1978). Counting Animals. Nairobi, African Wildlife Foundation.


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Appendix 1. List of aircraft and census crew who participated in the Ruaha-Rungwa ecosystem census conducted in October-November 2013.

Aircraft 5H-CFA 5H-TNP 5H-MPK

Pilot David Moyer (Lungu Ltd)Mackiyu Kajwangya (TANAPA)

Wellness Minja (WD)

FSOWilfred Marealle (TAWIRI)

Anna Laroya (TAWIRI)Hamza Kija (TAWIRI)

Left RSO Samwel Bakari (TAWIRI) Hellman Nyanda (WD)Chediel K Mrisha (TAWIRI)

Right RSO Migezo Azori (WD)Goodchance Chao(TANAPA)

Greyson Mwakalebe (TAWIRI)

Appendix 2. List of other participants of the October-November 2013 census in Ruaha-Rungwa ecosystem.

Logistics and Coordination

Honori Maliti, Edward Kohi (TAWIRI), Ole Mein’gataki, Christopher Timbuka, Paul Banga (TANAPA), Julius Kibebe (WD)

Data entry Damari Samwel (TANAPA), Edward Kohi, Mwita Machoke(TAWIRI)

Data Validation and Verification

Simon Mduma, Stephen J. Nindi, Edward Kohi, Samwel Bakari, HamzaKija, Mwita Machoke and Honori Maliti, (TAWIRI), Howard Frederick (CRC)

Data analysis Simon Mduma, Edward Kohi, Mwita Machoke (TAWIRI), HowardFrederick (CRC)

Mapping & Geo-referencing

Hamza Kija, Mwita Machoke (TAWIRI), Howard Frederick (CRC)

Report writingSimon Mduma, Stephen J. Nindi, Edward Kohi, Samwel Bakari, HamzaKija, Mwita Machoke and Honori Maliti, (TAWIRI) and HowardFrederick (CRC).

Documents

RuahaPrReport 2013-03