Fewer vultures, more wild dogs linked to greater disease risks

Scavenging is a highly important ecological process, playing a crucial role in the circulation of nutrients, the stabilization of food webs, and the mitigation of disease transmission to humans and among various other species. Vultures are some of the most important scavengers worldwide. By eating rotting carcasses that can become hotbeds of disease, and passing them through their highly acidic digestive systems which efficiently wipe out pathogens, vultures play a fundamental ecological role. 

Unfortunately, a new longitudinal study led by HawkWatch International and the University of Utah has found that vulture populations have been declining in recent decades. 

The researchers studied scavenger ecology at six abattoirs in Ethiopia with in-person survey and time-lapse photography from 2014 to 2019. They discovered that critically endangered Rüppell’s (Gyps rueppelli) and white-backed (G. africanus) vultures declined by 73 percent, while critically endangered hooded vultures (Necrosyrtes monachus) declined by 15 percent during this period. 

By the end of the study period in 2019, the carrion consumed by vultures year had dropped by 20,000 kg as a result of the declining populations. At the same time, the number of scavenging feral dogs has been steadily increasing, making researchers worry that this may lead to rabies outbreaks.

“We know that the vultures are declining and we know that the feral dogs are increasing, but we don’t know exactly why,” said study lead author Evan Buechley, the International Programs Director at HawkWatch. 

“Although we can’t say for sure if the decline represents a population crash or if the vultures are being displaced by dogs and moving away from the abattoirs, either way this is really concerning,” added study co-author Megan Murgatroyd, a conservation biologist at HawkWatch.

According to the researchers, the rise of feral dogs may increase rabies rates in humans, as it happened in the late 1990s in India and Pakistan, when vulture populations crashed and feral dog populations rose to take advantage of the uneaten carrion. Although it is not yet clear whether there will be a similar link between spikes in feral dog populations and rabies in Ethiopia too, this country is already burdened by approximately 3,000 deaths caused by rabies each year, most of them children.

“Unlike a lot of diseases which impact the elderly, rabies disproportionately affects young children, which are the most likely to be bit by rabid dogs,” said Buechley. A solution to avoid this could be to improve fencing around abattoir facilities, which would help restrict access by feral dogs, and hopefully increase foraging by vultures.

“The overarching point is that vultures are super important. If they decline, we expect there to be pretty profound ecological consequences and there may be increases in human disease burden. And so we should appreciate vultures and invest in their conservation,” Buechley concluded.

The study is published in the Journal of Wildlife Management. 

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By Andrei Ionescu, Earth.com Staff Writer