African Vulture Research: October 2015 Update

African Vulture Research: October 2015 Update

Introduction
The Southern Highlands of Tanzania has been identified as an area with a critical gap in researchers’ existing knowledge. However, based on current research, it appears to be a stronghold for vultures, where abundance is high and threats are currently low. Using roadside counts, researchers from the Wildlife Conservation Society (WCS), the Tanzania National Parks Authority (TANAPA) and the North Carolina Zoological Park (NCZP) have, since 2013, conducted surveys of vulture abundance. Consistent survey routes in Katavi National Park and Ruaha National Park were established. Initial surveys in 2013 and 2014 were only conducted in the dry season, while survey efforts were expanded to the wet season in 2015. A satellite telemetry study was also initiated in 2015. Using satellite telemetry, researchers will be able to better understand vulture movement patterns in the region, which in turn will further help inform survey efforts and findings.

Vehicle Surveys
In March 2015, four road transects covering 348.2 kilometers were successfully completed in Ruaha. In April 2015, three transects of 216.9 kilometers were completed in Katavi National Park. In addition, all seven transects were repeated in September 2015 with 361.7 km covered in Ruaha and 231.8 km covered in Katavi.

While trends should not be extrapolated from three years of data, it is useful to note that vulture abundances have not changed dramatically during the study as would be expected if poisoning rates had increased significantly. Across all three years, White-backed vultures were the most common scavenging raptor, followed by Bateleurs. In Katavi National Park, White-backed vulture encounter rates were considerably higher in 2015 than in previous years, but encounter rates for all other vulture species were lower than in previous years. In Ruaha National Park, White-backed vulture encounter rates were lower than in previous years, but encounter rates for all other vulture species were higher than in previous years. Notably, White-backed vulture abundance was considerably lower in the wet season than in the dry season. We suggest that this may be caused by a homerange expansion for the population, whereby vultures move out of the Katavi and Ruaha National Parks during the wet season, when food availability is likely to be lower.

Average number of individuals recorded per 100 kilometers for each species in Ruaha National Park, Tanzania

Species
Status
Ruaha NP 2013
Ruaha NP 2014
Ruaha NP 2015 (Wet)
Ruaha NP 2015 (Dry)
White-backed Vulture
45.3
50.9
17.9
33.9
Bataleur
15.0
18.9
15.3
14.6
Tawny Eagle
Least concern
8.1
3.7
1.0
6.0
White-headed Vulture
Vulnerable
4.1
2.3
2.8
3.9
Hooded Vulture
Endangered
9.7
4.8
1.5
5.5
Lappet-faced Vulture
Vulnerable
3.5
2.8
2.8
5.6
Ruppell’s Vulture
Endangered
0
0
0
0

 

Average number of individuals recorded per 100 km for each species in Katavi National Park, Tanzania

Species
Status
Katavi NP 2013
Katavi NP 2014
Katavi NP 2015 (Wet)
Katavi NP 2015 (Dry)
White-backed Vulture
Endangered
27.6
22.7
20.8
52.4
Bataleur
Near threatened
19.1
7.4
12.2
10.0
Tawny Eagle
Least concern
0.6
0
0
0
White-headed Vulture
Vulnerable
0.6
0.5
3.4
0
Hooded Vulture
Endangered
0.3
4.2
0
0.4
Lappet-faced Vulture
Vulnerable
0
4.8
1.0
0.9
Ruppell’s Vulture
Endangered
0
0
0
0

 

Satellite Tracking
Using satellite telemetry, we will be able to better understand vulture movement patterns in the Southern Highlands of Tanzania, which will further help inform survey efforts and findings. We still have few nesting records for vultures and other raptors in both Ruaha and Katavi. More effort is needed to establish vulture breeding densities.

On 15 September 2015, two White-backed vultures were tagged outside of Ruaha National Park. The satellite tags will deliver 14 data points per day (between 6:00 AM to 7:00 PM hourly and again at 12:00 AM) for at least one year. Telemetry data will be used to establish population ranges, to discover important breeding sites, and to determine principle mortality causes and rates. It is currently not known if Ruaha and Katavi parks represent a single vulture population; telemetry data will also help to explain any trends in abundance data collected during surveys.

Satellite Telemetry Study Methods
Vultures were trapped outside Ruaha National Park near Tandala Camp Site. Vultures were trapped using nooses, set up as lines, along carcasses. Noose-on-noose lines were made of coated wire cord or monofilament, and noose lines were made of parachute cord. Nooses were 10-15 centimeters in diameter.

Noose-on-noose lines were staked into the ground using tent pegs for added stability. Grass or carrion was used to help hold the nooses upright to increase the chance of a capture. Noose lines consisted of approximately 10 nooses. Once a bird was captured, processing took approximately 20 minutes per bird; birds’ eyes were covered to reduce stress and the handler restrained both feet and head.

Seventy-gram solar-powered ARGOS/GPS PTT tags were attached as backpacks using Teflon ribbon to two White-backed vultures on 15 September 2015. Backpacks used to attach the transmitters included a hemp-stitched weak point designed to allow the pack to fall off within a few years, as recapture of tagged individuals is generally infeasible.

Preliminary Results from Satellite Tagging
This represents the first movement study of vultures in Tanzania. Telemetry data will be used to establish population ranges, discover important breeding sites, and determine principle mortality causes and rates.

With only a few weeks of data no major conclusions can be made at this time. However it appears that one of the tagged vultures has a nest and is breeding while the other is not, which should make for an interesting comparison. So far both birds have remained primarily within Ruaha National Park, but have been using very different areas within the park. Both vultures have traveled cumulatively over 400 kilometers per week since being tagged.

We hypothesize that the vulture’s ranges will expand during the rainy season when food availability within Ruaha National Park begins to decline. There is potential that they will travel to other nearby protected areas, such as Katavi National Park, Selous Game Reserve, and perhaps even Niassa Game Reserve in Mozambique.

Future Research
Plans to continue vulture monitoring include repetitions of the road transects, ideally done four times per year (twice in wet season and twice in dry season), although it is likely that only two transects may be completed per year in Katavi. Information on vulture nests and vulture counts at carcasses is also requested from rangers and guides. Systematic nest searches by car and by aerial surveys should be conducted to further establish the abundance and to monitor population trends. Finally, we hope to obtain funding for further telemetry work and to tag an additional eight White-backed vultures.

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African Vulture Research: 2014 Summary
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Using road surveys, researchers continue their work focused on vultures located in two national parks in Tanzania. Conclusions about vulture movements in that region of Africa leads the researchers to a decision to initiate satellite... Read More