BOISE, Idaho – Vultures in one of Africa’s most significant wildlife reserves are declining at such an alarming rate that at least three species are threatened with extinction, according to a new study by The Peregrine Fund, National Museums of Kenya, and Princeton University.
Researchers found that vulture populations around the Masai Mara National Reserve in southwestern Kenya have dropped up to 60 percent over three decades. The primary causes are changes in land use and other human activity, particularly the poisoning of livestock carcasses intended to kill lions and other large predators. Vultures quickly die after scavenging on the tainted carcasses.
“Staggering declines in abundance were found for seven of eight scavenging raptors surveyed,” said co-author Munir Virani, director of The Peregrine Fund’s Africa-based programs. “Better land management and a ban on certain pesticides are needed to preserve these keystone members of the scavenging community.”
In addition to Virani, the study was co-authored by Corinne Kendall, Peter Njoroge, and Simon Thomsett. The peer-reviewed paper was published online Nov. 25 in Biological Conservation.
The study recommended that three species – African white-backed, Rüppell’s, and Hooded vultures – be relisted as Vulnerable on the IUCN Red List, an international compilation of threatened species. No Egyptian vultures were observed during the field studies, leading the authors to call for additional research to determine the status of this and other types of vultures. . “The situation in Kenya perhaps mirrors the situation throughout eastern Africa,” Virani said. “This is the first time that large-scale population declines in vultures and other scavenging raptors in and around the Masai Mara have been documented.”
Another study published in early 2010 by the Journal of Raptor Research showed similar trends for vultures elsewhere in Kenya. Research by Darcy Ogada, of The Peregrine Fund and Mpala Research Centre, and Felicia Keesing, of Bard College, revealed declines of 70 percent for scavenging birds, primarily vultures, over a three-year period in central Kenya. The authors determined that food and weather were not limiting factors and suggested that poisoned bait was responsible for the die-offs.
“The impacts of poisoning on vultures are happening throughout Kenya,” Ogada said.
The latest study by Virani, Kendall, Njoroge and Thomsett compared trends between the migration season of large ungulates like wildebeest and the non-migration season on reserve, buffer, and grazed lands. Large declines in all areas, including the reserve, during the ungulate migration – when food supplies are abundant for vultures -- suggest that they are affected well beyond the study area.
In many areas, livestock owners misuse a pesticide called Furadan to poison lions and other large predators that kill their livestock. They set out a carcass laced with the poison, which is subsequently scavenged by vultures. Because they are social animals that feed together, many vultures can be killed by a single poisoning event.
Scavengers occupy an essential niche in the ecosystem as a clean-up and recycling crew. Vultures quickly consume the carcasses of dead animals before they decay and develop diseases harmful to humans, livestock and wildlife.
Link to the abstract in Biological Conservation (fee for full article): http://dx.doi.org/10.1016/j.biocon.2010.10.024
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