New research shows vultures focus on regions where wildlife are most likely to die
Vultures track wildlife vulnerability, not abundance, in East Africa
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African vultures are famous for quickly finding carcasses, so much so that they are considered clairvoyants in parts of Africa. But just how do vultures know where to find food across vast regions in the first place? In a paper appearing in the January 8 edition of the international journal PLoS ONE, Hawk Mountain Research Associate Dr. Corinne Kendall and study colleagues have discovered that vultures, rather than aggregating where animals are most abundant as previously thought, instead focus on areas and conditions where animals are most likely to die. The complete article can be found online at PLoS ONE now.
Kendall is a lecturer at Columbia University and the African Vulture Technical Advisor with the Wildlife Conservation Society, and works in collaboration with Dr. Munir Virani at The Peregrine Fund, Dr. Hopcraft of Frankfurt Zoological Society, Dr. Keith Bildstein of Hawk Mountain Sanctuary, and Dr. Dan Rubenstein of Princeton University. Dr. Rubenstein also serves on the Hawk Mountain board.
Protecting these critical scavengers, which helps to keep the African savannas clean and reduces the risk of rabies and other disease, is the focus of a new effort by Hawk Mountain Sanctuary, the Peregrine Fund and the Wildlife Conservation Society.
For decades, scientists have assumed that vultures follow the largest food source available. In the case of the Mara-Serengeti ecosystem, this would be the migratory wildebeest herds, which in recent years have numbered in the millions. Instead, this study found that two of the three species of vultures studied preferentially selected areas of low rainfall and thus presumably high prey mortality.
Data were collected from GSM-GPS telemetry devices attached to three species of vultures in East Africa. The devices send text messages back to the researcher detailing individual bird’s location and altitude. The data revealed that vultures focused on the immense wildebeest herds only during the dry season when hundreds of wildebeest die each day from starvation or drowning during their dangerous river crossings.
“Our study shows that vultures seek out areas not where wildlife are most abundant, but where they are most likely to die,” said lead author Corinne Kendall. “This shows that for vultures, prey mortality is more important than prey abundance.”
The team found that during the rest of the year, vultures travel enormous distances in search of food.
“What really surprised us is that from November to June, the vultures travel all over Kenya and Northern Tanzania, with some individuals using an area of more than 200,000 square kilometers (77,000 square miles) -- that’s a region larger than New Jersey and New York State combined or roughly the size of the entire United Kingdom,” Kendall said.
As one of the only obligate scavengers in the animal kingdom, vultures are specially adapted to feed on dead animals, or carcasses.
Keith Bildstein, Sarkis Acopian Director of Conservation Science at Hawk Mountain Sanctuary, and a study co-author says the findings reveal important new information. “We already knew that vultures use efficient soaring flight, keen eyesight, and even used information from each other to find food, but we had a poor sense of how they decide where to search across a landscape,” he explains.
In recent years, these large movements have spelled disaster for the birds. White-backed vultures and Ruppell’s vultures, two of the species studied, have been up-listed to “Endangered” due to dramatic declines throughout the African continent.
Because vultures spend so much time outside of protected areas, they are extremely susceptible to poisoning, which often occurs when ranchers put pesticides on the carcasses of cows and other animals killed by lions or hyenas. “You can imagine how difficult it is to protect a species that uses not just multiple parks, but also spends a lot of time in areas that are completely unprotected,” says researcher and co-author Dr. Munir Virani.
Dr. Steve Zack, Coordinator of Bird Conservation at the Wildlife Conservation Society, is working with Dr. Kendall and others in shaping a conservation effort to revive vulture populations while eliminating the poisoning, and the findings will help the effort. “This new knowledge makes clear that engaging local communities well beyond park boundaries is needed to confront and eliminate the poisoning,” he says.
Celebrating 80 years in raptor conservation, Hawk Mountain Sanctuary is the world's first refuge for birds of prey and an international center for raptor conservation. It's far-reaching conservation science and education programs help to train the next generation of raptor biologists and to promote understanding of raptors globally. Hawk Mountain also conducts collaborative research on raptor migration ecology, which is designed to better protect both common and endangered raptors worldwide.