Scavenger Hunt

One of the world’s best known wildlife preserves is losing some signature birds. Vulture populations in and around Kenya’s Masai Mara National Reserve have experienced “staggering declines” over the last 30 years, a new study concludes. Habitat destruction and the use of powerful poisons appear to be behind the crash, which researchers say has placed several species at a greater risk of extinction.

These are not easy times for vultures, large soaring birds that typically feed on carcasses. Across Asia and Africa, populations are dropping due to habitat loss and the widespread use of livestock drugs that are lethal to birds that eat the tainted meat. Another threat comes from carcasses that local people have intentionally laced with pesticides or other poisons to kill lions, hyenas and other scavengers they view as a threat to their goats, cows and sheep.

Researchers have already documented vulture declines in Western and Southern Africa. To survey the situation in East Africa, a multi-national team of researchers compared roadside bird surveys done in and around the Masai ecosystem in 1976 and 1988 to data collected between 2003 and 2005. Overall, the team saw declines in six of the seven kinds of vultures they studied, and in one of two species of scavenging eagles. Only the Bateleur eagle (Terothopius ecaudatus) showed an increase, they report in Biological Conservation.

The biggest abundance drop – 62% — was seen Hooded vultures (Necrosyrtes monachus), while Egyptian vultures (Neophron percnopterus) disappeared entirely. And, on average, raptor abundance dropped from 100 birds per 100 kilometers of road to just 35. The researchers caution, however, that those numbers probably “represent an underestimate of actual population losses.”

One probable cause of the declines, the researchers write, is the ongoing conversion of lands outside the Masai Mara reserve to farming, grazing and tourism. That has helped drive steep declines in regional herds of large grazing mammals, including an 80% drop in resident wildebeest numbers. And the fact that vultures are disappearing within the reserve suggests that “human activities occurring in other parts of the species’ range, such as poisoning of carcasses, may be causing their decline.” In one case, a researcher documented a single poisoned carcass killing 187 vultures.

At a minimum, the researchers conclude that three kinds of vultures — African white-backed (Gyps africanus), Rüppell’s (Gyps rüppelli) and Hooded – should now be considered “vulnerable” species. And to protect the birds long-term, they say Kenya and other nations will need to do more to protect habitat, and ban the use of some chemical poisons. David Malakoff | December 2, 2010

 

Source: Virani, M., Kendall, C., Njoroge, P., & Thomsett, S. (2010). Major declines in the abundance of vultures and other scavenging raptors in and around the Masai Mara ecosystem, Kenya. Biological Conservation DOI: 10.1016/j.biocon.2010.10.024

Image © Eric Gevaert | Dreamstime.com

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