Why You Should Love Vultures Part 2: Because Nobody Does It Better
Image of white-backed vultures by Dr Jessica Bodgener
The vulture may not be your traditional wildlife conservation poster boy.
Indeed, you may struggle to see the beauty in the scrawny neck, bald head and fearsome beak of your average vulture, but looks can be deceptive. The negative reaction their appearance traditionally belies the absolutely vital role they play, as a keystone species, in keeping ecosystems, and all life they support, healthy.
Vultures, like other scavengers, often get a bad rap for being ‘unclean’ and yet the truth is quite the opposite. Natural scavengers play a vital role in keeping the environment clean, containing pathogens and recycling nutrients. In the case of vultures, they are nature’s most efficient clean-up merchants, working together to strip a cow or deer carcass to the bone in as little as twenty minutes. This key ecosystem service improves sanitation and reduces the risk of disease outbreaks, but relies on large and stable populations of vultures.
Our last news story considered the unprecedented and devastating decline in vulture numbers, on the Indian subcontinent in the 1990s, and how it was eventually traced to unintentional and unexpected poisoning by the NSAID diclofenac, the use of which had rapidly become extremely widespread, after it came off patent in India in 1994. The expiry of the patent meant that cheaper generic equivalents could be manufactured locally for the first time, making it accessible and affordable for veterinary use. It rapidly became the drug of choice for treating pain and fever in cattle. And inadvertently caused the death of millions of vultures.
We now look more closely at the consequences for the health of others who share the same ecosystems, as vulture numbers plummeted from an estimated 40 million to just a few thousand. Evidence posited by new research suggests that there has been a ‘meaningful increase in human mortality after vultures died out and were no longer removing carcasses from the environment’, underlining the importance of a One Health approach to biodiversity loss and restoration.
The speed and efficiency with which vultures are able to dispose of a carcass means deadly bacteria don’t have time to multiply and spread. Powerful stomach acid, with a pH which is up to 100 times more acidic than that of humans, combined with high body temperatures, allows vultures to ingest carrion infected by bacteria such as anthrax without any ill-effects. They are effectively a dead end for a whole host of dangerous pathogens, from TB, cholera and brucellosis to foot-and-mouth and rabies, which can knock out the rest of us - humans, livestock and other wildlife.
Prior to the catastrophic crash in their numbers, vultures were estimated to safely dispose of 12 million tons of carrion annually in India. With their demise, millions of carcasses were left to rot, typically taking three to four times longer to decompose, and significantly increasing the risk of disease being spread. The vacuum left by the massive loss of vultures was quickly filled by other less efficient mammalian scavengers, like rats and dogs. In particular, there was an explosion in the number of feral dogs, who benefitted from the lack of competition and greater availability of food. An estimated increase of a staggering 5.5 million feral dogs in India coincided with tumbling vulture numbers. At one carcass dump site in Rajasthan, numbers of dogs went from about 100 to 1,200 as carrion became more available, and they were found to be bringing up puppies literally in the ribcages of carcasses.
Dogs and rats ingest the rotting meat and can become carriers of any pathogens or parasites present – spreading disease to other species, including humans. The sudden increase in feral dogs is thought to have been at least partially responsible for an increased incidence of rabies, which killed 47,300 people in India between 1992 and 2006. Recent evidence has also revealed that sales of rabies vaccines increased sharply after 1996, as vulture numbers plummeted.
But the estimated 30% increase in feral dog numbers overall hasn’t just resulted in more cases of rabies. Dogs are becoming generally more aggressive (especially post the Covid pandemic) and have begun to hunt in packs and attack humans, with particularly deadly results for small children. Just last month there was a report of two young brothers, aged five and seven, being killed by dogs in southwest Delhi.
A recent study has also considered the impact of the loss of vultures on water quality, which can be negatively affected by farmers dumping carcasses in bodies of water, as well as through erosion caused by surface run-off, which can potentially move pathogens considerable distances.
The knock-on impact on human health is undeniable. One estimate of the economic cost of the vulture decline puts it at $34 billion over the thirteen years up to 2006, if medical treatment costs, loss of life and lost income are taken into account. Recent research has looked more closely at the all-causes human death rate in areas which were once prime vulture habitat, revealing an increase of at least 4.2% between 2000 and 2005 alone, which the authors hypothesise is a consequence of the catastrophic drop in vulture numbers.
Essentially, thanks to their efficient scavenging, vultures perform a vital ecosystem function. The species that have expanded to fill the vacuum left by the vultures, like rats and dogs, are not only less efficient at scavenging and likely to become carriers of disease, but they also tend to live more closely with humans, increasing risks to human health.
It is in the interests of all who share these ecosystems – vultures, other wildlife, domestic animals and people – to make sure these literally irreplaceable birds continue to recover their numbers and help secure their continuing recovery and survival over the coming decades.
Look out for our next article to find out more about the work of the incredibly dedicated people who are doing everything they can to save vultures, and what needs to happen next to ensure these remarkable birds survive and help us all to stay healthy.
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 Frank, Eyal and Sudarshan, Anant, TheSocial Costs of Keystone Species Collapse: Evidence from the Decline ofVultures in India (January 5, 2023). University of Chicago, Becker FriedmanInstitute for Economics Working Paper No. 2022-165; p5 Available at SSRN: https://ssrn.com/abstract=4318579 or http://dx.doi.org/10.2139/ssrn.4318579
Figure from RSPB/Bombay Natural History Society
Frank, Eyal and Sudarshan, Anant, The Social Costs of Keystone Species Collapse: Evidence from the Decline of Vultures in India (January 5, 2023). University of Chicago, Becker FriedmanInstitute for Economics Working Paper No. 2022-165; p5 Available at SSRN: https://ssrn.com/abstract=4318579 or http://dx.doi.org/10.2139/ssrn.4318579
 Frank, Eyal and Sudarshan, Anant, TheSocial Costs of Keystone Species Collapse: Evidence from the Decline ofVultures in India (January 5, 2023). University of Chicago, Becker FriedmanInstitute for Economics Working Paper No. 2022-165; p4 Available at SSRN: https://ssrn.com/abstract=4318579 or http://dx.doi.org/10.2139/ssrn.4318579