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In the yards behind the slaughterhouses – also called abattoirs – of Ethiopia, an ecological shift is taking place that echoes similar crises all over the world. Species with a clear and efficient ecological role are in serious decline, and the less specialized but more aggressive species that have moved in to take their place are not only less efficient, but harming their ecosystem which, in this case, includes humans. .
It’s a story of vultures, wild dogs, rage and piles of rotting animal carcasses. Buckle up. But ultimately, it’s about the power of conservation to keep ecosystems, even urban ecosystems, in balance for the benefit of the people who live there.
“Carrion consumption by vultures is decreasing and increasing by most other scavengers, but this increase is not enough to offset the loss of vultures.” says Evan Buechley, a graduate of the University of Utah now with The Peregrine Fund, “So there’s a gap there. And what happens with that gap is a bit of an unanswered question, but therein lies the problem.
The study is published in the Wildlife Management Journal and is funded by the National Science Foundation, the University of Utah, HawkWatch International, the Peregrine Fund, and the National Geographic Society.
Vultures are awesome
All over the world, vultures are perfectly equipped to deal with the nasty remains of death. Rotting carcasses can become disease hotspots, invaded by bacteria and insects. But the vultures are an effective cleanup team. By eating carrion, they remove the carcasses and pass them through a highly acidic digestive system which eliminates pathogens. And a diversity of vultures is better – some species are specialized in tearing off hides and skins while others, coming last, literally gobble up bones.
But the vultures have been struggling in recent decades. They are sensitive to poisons in the carrion they eat, whether lead ammunition, the drug diclofenac, or poisons used against predatory animals. And because vultures produce relatively few chicks and take a relatively long time to mature, it is more difficult for them to recover from population declines.
Çağan Şekercioğlu, an associate professor at the School of Biological Sciences at the University of Utah, showed that vultures are the most endangered group of birds (called an ecological guild, when the group uses the same resources or related resources) in 2004 when he conducted the first known ecological study. analysis of all bird species during his graduate studies.
In 2012, Şekercioğlu accepted Buechley as his first doctoral student at the U. Buechley brought extensive experience working with vultures and condors. He and Şekercioğlu started a project monitoring Egyptian vultures in eastern Turkey and the Horn of Africa.
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“Evan led this project brilliantly and extended it to other vulture species in Ethiopia and the Horn,” says Şekercioğlu. “Despite the many challenges, he also decided to study the scavenger communities of Addis Ababa slaughterhouses, in order to quantify the causes and consequences of the decline of vultures in the region.”
In 2016, Şekercioğlu and Buechley reanalyzed the ecology of all bird species. “We realized that vultures not only have the fewest species of all avian ecological guilds, which makes them irreplaceable, but since that first analysis in 2004, they have fallen faster than any other group,” says Şekercioğlu.
Yes, there are other scavenger species that can take the place of vultures at the scavenger table. But the loss of vultures, as we will see, can come with human costs.
The feathered “employees” of slaughterhouses
At Ethiopia’s slaughterhouses, vultures are welcome partners. After slaughtering the animals under clean conditions, workers move the remains of the carcasses – hooves, organs and bones, for example, to separate the compounds. It’s a . . . unique sensory experience, says Buechley.
“It can be quite stinky and quite gross, by any objective measure.”
Slaughterhouses are therefore grateful to the scavengers, including the critically endangered white-backed, Rüppell’s and hooded vultures, who eagerly clean up the pile.
Study co-author Alazar Daka Ruffo of Addis Ababa University interviewed slaughterhouse staff to find out what they think of vultures.
“Some slaughterhouse staff say half-jokingly, but not entirely, that they consider vultures to be slaughterhouse employees,” Buechley says, reporting Ruffo’s findings. “They perform an important function. There is an intentionality behind the system.
Other winged scavengers frequent the heaps, including ravens, ravens, ibises, and marabous. Four-legged visitors include packs of wild dogs.
“It’s an urban ecology situation where the human food supply really meets and interacts directly with the food supply of scavenger wildlife,” Buechley adds. “It’s just a really complicated, crude but fascinating system.”
With a research team including Rebecca Bishop, Tara Christensen and Şekercioğlu from the U School of Biological Sciences, Buechley set out to quantify the amount of carrion consumed by scavengers at six slaughterhouses in Ethiopia over five years, from 2014 to 2019.
Decline of vultures and increase in rabies
The team noted the types and abundance of scavengers that visited the slaughterhouse buffets, and used this to extrapolate how much they ate. At first, the vultures ate more than half of the carrion in the dumps. White-backed, Rüppell’s, and hooded vultures together ate an average of about 550 pounds (250 kg) of carrion per day.
But at the end of the five-year study, the number of Rüppell’s vultures and white-backed vultures visiting slaughterhouse disposal pens decreased by 73%. Hooded Vulture visits decreased by 15%. During the same period, wild dog detections more than doubled.
“While we can’t say for sure if the decline represents a population crash or if the vultures are being moved by dogs and away from slaughterhouses, either way it’s really concerning,” says Megan Murgatroyd. , Acting Director of International Programs for Hawk Watch International.
“We know vultures are declining and we know wild dogs are increasing, but we don’t know exactly why,” Buechley says, adding that slaughterhouse practices are also changing and more studies will be needed to establish a clear picture. cause-relation and-effect.
Either way, vultures can ill afford the loss of slaughterhouses as a food source. Rüppell’s, white-backed, and hooded vultures are listed as critically endangered. “It’s the highest category of threat before it becomes extinct or extirpated in the wild,” Buechley says.
The Rüppell’s Vulture population has declined by more than 90% over the past three generations (about 40 years). White-backed and Hooded Vultures are doing a little better, but not much. They are estimated to have declined by 81% and 83%, respectively, over three generations.
“So it seems that their disappearance from slaughterhouses is probably linked to a population crash,” says Murgatroyd. “The vultures need all the help they can get right now, and having to compete with growing dog populations is only making things worse.”
Other rising scavengers including dogs, ibises and corvids (crows and ravens) were unable to take over slaughterhouses. In 2019, scavengers were consuming nearly 43,000 pounds (about 20,000 kg) less carrion per year than they were in 2014, when vultures were more abundant and dogs rarer.
A frightening consequence of the increase in the number of dogs can be an increase in rage rate in men. In the late 1990s, vulture populations in India and Pakistan collapsed. Wild dog populations have increased to take advantage of uneaten carrion.
“They are also vectors of disease,” says Buechley, “and they interact very closely with people. And there has been a link between a surge in wild dog populations and rabies in India. »
Is the same likely to happen in Ethiopia? Scientists have not yet established a link between the loss of vultures and the increase in rabies in this country. But Ethiopia already bears a heavy burden of rabies with around 3,000 deaths from the disease a year.
“Unlike many diseases that affect older people, rabies disproportionately affects young children, who are most susceptible to being bitten by rabid dogs,” Buechley says.
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