Around 1,000 vultures have been found dead in Guinea-Bissau in the last two weeks, believed to have been poisoned.
The birds, almost all critically endangered hooded vultures (Necrosyrtes monachus) were found in different locations across the country, with the majority near the towns of Bafata and Gabu.
Initial details suggest that the birds were poisoned, although more information is needed to be sure of the cause.
“This is one of the largest mortality incidents of vultures for a long time,” Jose Tavares, director at the Switzerland-based Vulture Conservation Foundation (VCF), which has been following the incident and coordinating information with stakeholders, told Mongabay.
Worryingly, Tavares added, with the cause of death still unidentified, more birds could yet be killed.
“The hooded vulture is a critically endangered species and while rarer in eastern and southern Africa, western Africa is its stronghold. Losing so many birds in its stronghold is a major blow to the species,” he said.
Authorities in Guinea-Bissau who dealt with the incident reported that the vultures “were bubbling from their beaks while dying,” and that they seemed to be searching for water, which suggests poisoning to Tavares. And because sentinel poisoning is used by poachers only where there is big game — of which Guinea-Bissau has none — he said suspects the raptors died after eating carcasses poisoned in an effort to kill feral dogs.
To minimize the risk of further poisoning of vultures or other scavengers, authorities incinerated most of the bird carcasses. Only one vulture carcass has been kept for examination so far, but VCF is working with local authorities to collect more that can then be sent abroad for tests.
The incident highlights the threat that poison poses to vultures across the continent.
Vulture populations across Africa have declined rapidly over the last three decades —eight species considered in one survey had declined by an average of 62%. Poisoning has been identified as the biggest threat to the birds. They fall victim either through secondary poisoning, where they eat a carcass poisoned with the aim of killing predators, or through so-called sentinel poisoning by poachers.
In one such incident in Botswana last year, 530 vultures were killed when poachers laced elephant carcasses with poison to prevent circling vultures from leading rangers to the scene.
Darcy Ogada of The Peregrine Fund and her colleagues have shown that vulture populations in Africa face a number of threats: just under a third of vulture deaths are down to use of their body parts in belief-based practices, and almost a tenth are due to electrocution. However, almost two-thirds of deaths are due to poison.
“Electrocutions aren’t going to wipe out vultures. [But] poisoning will send them into extinction in Africa,” Campbell Murn, head of conservation and research at the U.K.-based Hawk Conservancy Trust, told Mongabay.
Conservationists have called for African governments to implement effective regulation on the sale and use of poisons, including for agricultural purposes, which are lethal to vultures, as well as harsh penalties for perpetrators of deliberate vulture poisoning.
But it can be a complex issue, especially in cases where poison is used to kill predators, such as in the case of farmers protecting livestock, or locals protecting themselves.
“Indiscriminate poisoning is not the answer. There are other ways of dealing with dangerous animals that do not have such an impact on other species, for instance, shooting, trapping, maybe even targeted poisoning,” Tavares said.
“Although obviously all of these are often more expensive or difficult and raise a lot of questions. It is an example of the historic wildlife vs. human conflict,” he added.
Sentinel poisoning is also difficult to address without dealing with poaching itself, Murn said.
However, if it is not dealt with, vultures could soon disappear in Africa.
“In some areas of Africa, vulture populations are in free fall. If nothing changes, we could see vultures effectively disappear from the continent in a few decades,” Murn said.
Without them, the crucial ecosystem services they provide, including limiting the spread of diseases between scavengers feeding on carcasses, could be lost.
In countries such as India, where vultures have been driven to the edge of extinction in recent decades due to poisoning, there has been a documented rise in the numbers of feral dogs — a carcass can support more of them as they do not have to share it with vultures — which act as a reservoir for diseases such as rabies.
Murn and other scientists are researching the role vultures play in the ecology of diseases such as anthrax and botulism, among others, and hope to provide clear evidence of whether they help to reduce the spread of specific diseases.
“Vultures provide valuable ecosystem services,” he said. “The role they play in providing them should not be overlooked.”
Ogada, D. L., Shaw, P., Beyers, R.L., Buij, R., Murn,C., Thiollay, J.M., … Sinclair, A.R. E. (2015). Another continental vulture crisis: Africa’s vultures collapsing toward extinction. Conservation Letters, 9 , 89-97. doi:10.1111 / conl.12182
Houston, D. C., & Cooper, J. E. (1975). The digestive tract of the whiteback griffon vulture and its role in disease transmission among wild ungulates. Journal of Wildlife Diseases, 11 , 306-313. doi:10.7589 / 0090-3558-11.3.306
Ogada, D. L., Torchin, M. E., Kinnaird, M. F., & Ezenwa, V. O. (2012). Effects of vulture declines on facultative scavengers and potential implications for mammalian disease transmission. Conservation Biology, 26 , 453-460. doi:10.1111 / j.1523-1739.2012.01827.x
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