New tracking paper from Nepal: Movements, survival rates and mortality causes of wild and released vultures

A paper just published in the international ornithological journal Ibis describes annual survival rates and home range sizes of wild White-rumped Vultures Gyps bengalensis and compares them to those of birds released from the conservation breeding programme in Nepal. A total of 99 birds were fitted with GPS telemetry devices between 2017 and 2022, 50 of them of wild origin, the remaining 49 released birds from the captive breeding population. The captive birds were only released because undercover surveys of veterinary pharmacies in Nepal had shown that almost none were selling diclofenac over a period of about five years before the releases began and because repeated road transect counts had shown that wild populations of both White-rumped and Slender-billed vultures had been increasing steadily since about 2012. For these two reasons, it was thought to be very unlikely that there would be significant exposure of vultures to diclofenac.

Results suggest that annual survival rates of wild birds are high – 97% and 88% for adult and subadult birds, respectively – and comparable to rates in stable or increasing populations of Gyps vultures studied elsewhere in the world. Although regularly returning to the Vulture Restaurant, the birds ranged over several thousand kilometres. By contrast, the released birds had lower survival rates, especially those released as adults, birds that had spent ca.10 years in captivity prior to release. The movements of released birds were also far more restricted, as the birds were more reliant on the supplementary food provided at the restaurant.

A wild tagged White-rumped Vulture in Nepal

Lead author Dr John Mallord of the RSPB Centre for Conservation Science commented “Vultures are large birds and, as such, one would expect them to have very high survival rates. However, during the Asian vulture crisis, vultures were suffering annual mortality of 40-50%, which led to their near extinction. Our results show that, following the removal of diclofenac, survival rates of vultures in Nepal are now at levels comparable to populations of vultures elsewhere in the world that are not impacted by extra sources of anthropogenic mortality. This further confirms the efficacy of the Vulture Safe Zone conservation work carried out by Bird Conservation Nepal in ensuring that diclofenac remains unavailable to veterinarians and livestock owners”.

Ankit Joshi, Vulture Conservation Officer at Bird Conservation Nepal (BCN) added “Our teams work tirelessly in the field, firstly in advocating the use of the vulture-safe NSAID meloxicam which was so instrumental in getting diclofenac banned in the first place, and also in monitoring all the tagged birds and following up on anything suspicious so that any birds that die can be swiftly located and sent for post-mortem analysis. By so doing, we have been able to confirm that no birds died of diclofenac, or any other NSAID, poisoning”.

Vulture biologist and former Vulture Conservation Officer at BCN, Krishna Bhusal commented that “Although the behaviour of the released birds was different to that of their wild counterparts, with their movements restricted to around the Jatayu Vulture Restaurant, where birds were initially released, it is hugely encouraging that several of the formerly captive vultures are now successfully breeding around the release site. We hope that their offspring will behave, and survive, in a manner more like other wild birds”.

Rhys Green, Professor of Conservation Science at the University of Cambridge, who has been involved in vulture conservation for over 20 years, added “Although populations of vultures in Nepal have increased rapidly over the last ten years, and have remained stable in India, their numbers are still very low compared to what they once were, so these species are still at risk of extinction. There are no regulatory mechanisms in any of the vulture range states in South Asia to prevent a new-to-market veterinary NSAID even more toxic to vultures than diclofenac being approved by the authorities tomorrow. Therefore, the maintenance of safety-net captive breeding populations is still a conservation imperative. Maintenance of the self-sustaining captive populations of all three critically endangered Gyps vulture species in India is of vital importance. Although released birds in our study had lower survival rates, lessons have been learnt that can help improve the success of vulture breeding and release programmes elsewhere in Asia”.

The high survival rates of wild vultures, the fact that no birds were found to have died from NSAID poisoning, and the rapid partial recovery of vulture populations in Nepal, confirm that the environment over which the tagged birds roamed is safe for vultures. Hence, in 2021, this area was declared the world’s first genuinely safe Vulture Safe Zone by the Technical Advisory Panel of SAVE.  It is also important to note that no tagged vultures died during monitoring because of deliberate use of poison baits set to kill carnivores such as dogs and jackals. Although there were poisoning incidents of this type recorded in Nepal during the study period, the satellite tracking results indicate that, on average, such poisoning kills vultures infrequently in Nepal.

Dr Sindhu Prasad Dhungana, Director General of Department of National Parks and Wildlife Conservation, Nepal, commented “The study and the findings further confirm that the removal of diclofenac has been effective due to the collective efforts of Government, NGOs, and local communities. Nonetheless, we need to be alert for other drugs and threats in a way that further recovery of these important birds can be maintained”.

At the height of the Asian vulture crisis, which began in the mid-1990s, vultures came close to extinction, with the worst-hit species, White-rumped Vulture Gyps bengalensis, declining by a staggering 99.9% in India in little over a decade. There were similar declines in neighbouring countries, including Nepal. The cause was unintentional poisoning by the veterinary non-steroidal anti-inflammatory drug (NSAID) diclofenac. This drug causes kidney failure and death when vultures feed on a cow which was treated with the drug before its death. This led to the ban on the veterinary use of diclofenac by governments across south Asia. Another measure that was implemented was the establishment of conservation breeding centres, firstly in India, then in Pakistan and Nepal, which are intended to hold self-sustaining safety-net populations.

Links:

Survival rates of wild and released White‐rumped Vultures (Gyps bengalensis), and their implications for conservation of vultures in Nepal – Mallord – Ibis – Wiley Online Library

First ever Vulture Safe Zone declared fully safe in Nepal at SAVE’s 11th Annual Meeting – Save Vultures (save-vultures.org)

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