India is home to nine species of vultures, all of which have faced dramatic population declines since the 1980s. Perhaps the most alarming, from both a social and ecological viewpoint, is the disappearance of the white-rumped vulture (Gyps bengalensis). The white-rumped vulture is a conspecific species, nesting in large flocks high in trees. Females lay a single egg during the short breeding season, which hatches after two months. Vultures are scavengers and feed on carrion, either fresh or putrid, due to its high protein content.
A Sudden Disappearance
Once the most common large raptor in the subcontinent, this bird has undergone a 99.7% decline over its home range. One of four vultures listed as Critically Endangered on the IUCN Redlist, this vulture is now regionally extinct in China, Myanmar, and Bangladesh. The decline of this species in India was first noticed in Keoladeo National park, and country-wide population decline was noted between 2000-2007.
The widespread decline of vultures across South and Southeast Asia can be attributed to two main causes: habitat destruction, and the use of anti-inflammatory drugs in livestock and human medications. Conservationists in India are no strangers to the repercussions of habitat loss, and unfortunately, neither are vultures. Habitat loss is seen both in India’s growing cities and towns, as well as in our once-intact forest patches. A lack of tall trees and the advent of skyscrapers has reduced the available roosting spaces for birds of prey. Cities such as Mumbai and Bangalore, which traditionally have had large, localised vulture populations due to their Towers of Silence, where Parsi communities leave their dead for sky burial, are now facing a vulture shortage. Indian cities have also experienced rampant population growth; Mumbai’s population grew from 10,391,000 persons (1985) to 22,046,000 persons (2018). Additionally, Mumbai saw the shifting of its slaughterhouses to the outskirts of the city, a blessing from a public health perspective, but detrimental to the efforts of keeping vultures thriving within the city. According to ornithologist Gautam Narayan of the Bombay Natural History Society (BNHS), the shifting of the slaughterhouses played a major role in the vulture scarcity in the city.
However, the use of Diclofenac, a classified non-steroidal anti-inflammatory drug (NSAID), to treat livestock is the most widespread and rapid killer of India’s vultures. The drug was cheap and widely available, making it the best option for India’s struggling cattle herders, until its ban in 2006. White-rumped vultures tested in laboratories with minimal Diclofenac (0.8mg/kg) died within a few days from extensive kidney failure; visceral gout was also observed in all specimens from the laboratory as well as those brought in from the wild post-mortem. Vultures are particularly vulnerable to poisoning from toxic substances due to their foraging behavior. First, multiple vultures feed at a single carcass at a time, causing large numbers of the species to be poisoned at a time if Diclofenac is present in the tissue of the carcass. Second, as vultures have a long lifespan and are at the top of the food chain, they are placed at risk of biomagnification.[1] Vultures are also exposed to a higher concentration of contaminants as they feed on carcasses and/or waste products. Thus, while their role in nature is vital to maintaining ecological balance, the very ecology of the species is pushing it further towards extinction.
Why do we care about vultures?
The smell is the first thing you notice. Then, the crowds of crows, jostling one another for space on the broad stone wall, their beady eyes fixed on some unseen prize. Then the kites, wheeling in the skies above, their shadows sending the rats scurrying into the dark recesses of the tower. But the rats don’t go far. They bide their time gnawing on bones already stripped clean of meat, every morsel removed. The crows hop nearer, after ascertaining that the most fearsome opposition they are facing are the kites. The odour intensifies. These bodies are rotting.
The sudden decline in India’s vulture population poses a grave hazard both to the ecosystem as well as to public health. A lack of vultures increases the number of decomposing carcasses deposited outside villages, leading to an increase in disease spread by parasites, flies, and ticks, as well as airborne diseases from the carcasses. In the case of human corpses that are fed on by vultures, as seen in the next section, diseases such as hepatitis A and B, human T-lymphotropic virus, and tuberculosis may be transmitted from the cadaver to pallbearers or social workers. Such workers may also be exposed to organisms that naturally exist in the gastrointestinal tract as corpses often leak fecal matter or body fluids in the time period immediately following death. Another consequence is the spread of rabies due to the increase in feral dog populations feeding upon the carcasses that used to be consumed by vultures.
A pile of dead cattle lying outside the village gate makes the children refuse to walk to school using their usual shortcut. The cloud of flies around the carcasses is thick, a black cloud buzzing agitatedly, and the feral dogs loitering around the pile try to build up the courage to break through the swarm. The flies crowd out the dogs, and the crows flutter closer as the dogs retreat, snapping up flies in their quest to access the rotting flesh. Another cart pulls out of the gate and shudders to a halt. The flies disperse momentarily as two men bodily hurl yet another dead cow onto the already-hulking pile of carcasses. Their faces are swathed in handkerchiefs, protecting them from the stench and the diseases festering in the rotting cattle. Until nature decomposes these cattle, the stench and the filth will only grow. The men return to their village. The dogs charge at the carcasses, scattering the flies.
From 1993 to 2006, indirect health costs due to vulture declines approximated $34 billion. Firstly, the reduction in vultures encourages feral dog populations that are attracted to carrion, as both species compete for easily obtained freshly dead meat. One vulture consumes approximately 0.5 kg meat/day while a dog can consume about 5.0 kg meat/week. By this calculation, the loss of one vulture would increase food availability for 0.7 dogs. Feral dogs have increased India’s rabies incidence rate to the highest in the world – 60% of all globally-documented cases. Of the 20,000 rabies cases recorded annually in India, 96% are from feral dog bites.
Additionally, vultures are the centerpiece of the death ritual known as sky burial, practiced by Parsis (Zoroastrians) living in India. Parsis leave their dead atop of round stone structures known as dakhmas, where vultures and smaller raptors devour the bodies, leaving behind only the bones. With the vulture decline, Parsis find themselves struggling to maintain this ritual. In Mumbai, a lack of vultures has led to a pileup of corpses on the Towers of Silence, which led the government to place solar concentrators on the towers to aid in rapid decomposition. However, these concentrators only work with ample sunlight; during the monsoon, bodies pile up and rot, and the risk of disease grows. Additionally, Diclofenac is an ingredient in certain human medications as well, and consuming human flesh from the Towers can also contribute to vulture declines due to residual Diclofenac in the tissue. Medical research has found multiple negative side effects of Diclofenac in humans, including gastrointestinal ulcers, internal bleeding of the stomach lining, renal injury, and adverse skin effects. A complete ban on Diclofenac in human pharmaceuticals is critical to maintain populations of newly released vultures that make their way to the Towers of Silence to feed, and given the detrimental health effects on humans, this ban seems imperative.
The Road to Recovery:
Medical research has pinpointed an alternative drug to Diclofenac – Meloxicam, which has been tested with limited side effects on livestock. The drug was, importantly, noted to be rapidly metabolized and excreted by vultures. Above-natural doses of Meloxicam, when administered to vultures, was found to have no detrimental effect, making it a viable alternative in veterinary medicine. The one limitation is the higher production cost, which makes it less accessible to rural farmers, but with further research, there is a high possibility that Meloxicam will eventually be more accessible to farmers and cattle herders.
On the conservation forefront are various stalwarts who are fighting for the return of this magnificent species. In 2004, the BNHS started a vulture breeding and care centre at Pinjore, Haryana. There are now nine centres across India, of which three are directly managed by the BNHS, and their primary purpose is to look after vultures, breed them in captivity, and eventually release them into the wild. According to BNHS Deputy Director Dr. Vibhu Prakash, the first objective of the programme was to produce a few hundred breeding pairs of the three endangered vulture species. After the 2008 ban on Diclofenac in veterinary medicines, a survey revealed about 6,000 white-rumped vultures, 12,000 long-billed vultures, and 1,000 slender-billed vultures in the wild.
If a stringent ban on Diclofenac is enforced, there is still hope for the return of India’s vultures. From an ecological and sociological perspective, vultures play a key role in maintaining natural cycles and balances. Without them, the risk of disease increase, as does the deterioration of ecosystem health. But the skies are looking up for India’s vultures, and soon, we may spot these winged beauties circling on thermal currents again.
This blog post is a longer version of a piece that I wrote for Conservation India in June 2020. The original version can be found here.
[1] Biomagnification occurs when the concentration of a substance in an organism’s tissues exceeds the background concentration of the substance in its diet; occurs as substances move up the food chain and their concentration in the animal’s tissues increases with each trophic level.
To Read More on India’s Vultures:
On Life and Wildlife 