In the heart of Rajasthan’s Thar desert, on the outskirts of the agro-pastoralist landscape of Bikaner, is a dumpsite of livestock carcasses where, traditionally, a feeding frenzy plays out among multiple species of beasts and birds everyday.
Importantly, every winter, a large number of migratory Himalayan and Eurasian griffon, whose numbers have dwindled catastrophically in the country, congregate at this dumpsite, located in the northwestern corner of Jorbeer Conservation Reserve of Bikaner. Other scavengers here are Egyptian vultures, steppe eagles, black ibises, cattle egrets and wild pigs, which feast on dead cattle, horses, camels, sheep and goats.
Now, a new study published in the journal Biological Conservation has found that perennially free-ranging dogs pose a serious threat to vultures here. This finding comes in the backdrop of other studies that have tracked the catastrophic decline in vulture populations in India: the raptor numbers plummeted by over 90% in the 1990s, largely due to the veterinary use of the anti-inflammatory drug diclofenac in livestock. When the cattle died, their poisonous carcasses killed the birds that fed on them in large numbers.
In several parts of India, vultures went extinct. An older study even corelated vulture decline to increased human deaths from a burgeoning feral dog population and the spread of rabies.
“As vulture recovery efforts continue, the presence of dogs at supplementary feeding sites [dumpsites] may hinder vulture access through direct competition and aggressive interference,” cautions the new paper.
Vulture restaurants
India’s vulture populations have historically been sustained by livestock carcass dumpsites, but with dogs increasingly in the mix, the scientists found that vultures spent about half as long on carcasses at the open Bikaner dumpsite than at dog-free enclosures. “Dog presence also altered their temporal feeding patterns, restricting vulture activity largely to the afternoon, whereas in the absence of dogs, feeding was distributed more evenly across daylight hours,” the paper added.
As dogs can consume large amounts of meat, it reduces food availability for vultures too; the canines also chase away the birds, reducing their access to carcasses. The paper concludes that dogs are “a major threat to vultures” here.
Dumpsites or ‘supplementary feeding sites’ are places where carcasses are regularly accessible to scavengers at a fixed location. In Europe and Africa they are usually managed “vulture restaurants” offering safe, drug-free carrion, co-author of the paper, Abi T. Vanak of Ashoka Trust for Research in Ecology and the Environment, told The Hindu.
“In India, traditional livestock carcass dumps were never designed for vultures, but their large and predictable carcass supply made them function as de facto feeding sites for vultures, as at Jorbeer in Bikaner,” he added.
Safe zones
While dumpsites function as a “highly predictable food resource[s]” for vultures, it is imperative that they are managed adequately, said the paper conceding that the “predictability” of such feeding sites “may promote the habituation of vultures,” diminishing their natural foraging activity across the reserve. Moreover, competitively superior species, such as large griffons, are more likely to monopolise the majority of this food resource available, thereby displacing subordinate species.
The impact of dogs on wildlife has been well documented.: the canines are known to have contributed to the extinction of 11 vertebrate species around the world. In India, they are known to prey on over 80 species, including black bucks, desert foxes and olive ridley turtles, according to a paper in the journal Animal Conservation. They have even been documented attacking snow leopards in Ladakh.
Prof. Vanak said that setting up more dispersed dog-proof feeding sites could encourage broader landscape level foraging by vultures, thus reducing their dependence on a single site. “Our study shows that conserving vulture populations will require more strategic management of food sources, including managing the populations of dogs, and creating vulture ‘safe zones’ where they can feed in peace,” he added.
divya.gandhi@thehindu.co.in