Vultures are often seen as unsightly outcasts in the animal kingdom, yet their dirty work is needed to keep ecosystems healthy. New research has shown that without these underappreciated scavengers, diseases would run rampant throughout the natural world.
A study recently published in Ecology and Evolution explains how declining vulture populations could have a devastating impact on the environment. Vultures have already begun to vanish across Europe, Asia, and Africa; now, concerns are also rising for vultures in the Americas, as their shrinking presence could eventually trigger a public health crisis that extends to humans.
Cleaning up the Environment
Vultures fulfill the vital role of consuming carrion, or the carcasses of dead animals. The reason they can stomach unsavory meals of rotting meat and bone is because of their highly corrosive stomach acid, with a pH just above 0 (the acidic extreme on the pH scale). Even stronger than battery acid, it allows vultures to digest flesh and eradicate harmful microorganisms.
By removing carrion from the environment, vultures contribute to nutrient recycling and keep contaminants from festering in soil and water. While other opportunistic scavengers like wolves and bears sometimes aid these processes as well, vultures remain the true champions of carrion consumption.
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What Will Happen If Vultures Disappear?
The new study warns of consequences that could follow the decline of “New World” vultures in the Americas.
“This research underlines the unique and irreplaceable role that vultures play as nature’s ‘clean up crew’,” said co-author Julia Grootaers, a behavioral ecologist at the University of Exeter, Cornwall, in a statement. “Unloved and unappreciated – even to the point of persecution – the importance of vultures is stark when you remove them from an ecosystem.
To gauge just how important vultures are in ecosystems, researchers went to Costa Rica and conducted fieldwork using domestic pig carcasses.
The researchers placed pig carcasses within 500 m. (approx. 1640 ft.) of each other, covering both forest and grassland areas. While half of the carcasses were available to all scavengers, the other half were put in a cage with netting, preventing larger animals (including vultures) from eating them. The researchers also set up cameras to record animal presence, as well as insect traps to keep track of flies and dung beetles.
Over the course of 10 months, they watched as Black Vultures, Turkey Vultures, and King Vultures visited 15 of the 16 sites. Other scavengers — pumas, ocelots, caiman, and coyotes — were rarely spotted.
When the researchers measured the rates of decomposition at the sites, they found that carcasses reachable by vultures lost an average of 9.5 kg. (nearly 21 lbs.) of mass each day. Meanwhile, the carcasses in cages lost an average of just 4.8 kg. (around 10 lbs.) each day.
In addition, the number of flies at the caged sites nearly doubled. When vultures are not able to consume carcasses, decomposition takes much longer, as the job mainly falls to insects and microbes. The extended duration of decomposition without vultures allows flies to reproduce at greater levels, causing more larvae to reach maturity. The resulting abundance of flies could then carry and spread diseases like botulism, anthrax, E. coli, and Salmonella.
Lessons from the Indian Vulture Crisis
The damage that follows local vulture extinction could be far-reaching, affecting not only animals but humans too. India has already seen its own version of a vulture population crash; in the 1990s, vultures nearly went extinct in the country because they were inadvertently ingesting a drug called diclofenac, once given to cattle for pain and inflammation (but banned from veterinary practice in the country in 2006). When vultures consumed cattle, the drug passed on to them and led to severe kidney failure.
Millions of vultures began to drop dead, leaving cattle to rot. This resulted in the spread of deadly pathogens and a rise in disease-carrying rats and feral dogs. Ultimately, about half a million people died from 2000 to 2005 from complications that could be traced back to the near-extinction of vultures. While the vulture population has stabilized since then, the scars are still left in the ecosystems there.
The study’s authors stress that vulture research and conservation need to continue to keep ecosystems safe from disease, especially since vultures in the Americas are starting to look more vulnerable than ever.
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Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.
