Dr. A. K. SINGH. 1
Vulture population in India is facing a catastrophic decline. Both species, white-backed vulture (Gyps bengalensis), and the long-billed vulture (Gyps indicus) common till recently, have drastically reduced by 95%, and almost completely in certain areas in a short span of two to three years. Sick and dead vultures have also been found in Nepal and Pakistan, raising concern of spreading towards west into other griffon vultures across Europe and Africa. This alarming decline has caused serious ecological imbalance. It's evident by the fact that, vultures have enormous capacity for scavenging dead, rotten, putrefied tissues, and can rip off a carcass into pieces of bones in no time. In their absence carcasses disposal is now at the mercy of crows, feral dogs, and maggots, which are available in abundance. This adds to several complications and collateral risks. In an unusual incidence at a village in the vicinity of Satpura forests area in Betul district of Madhya Pradesh, three apparently healthy vultures were seen along with several crows and dogs at a buffalo carcass kept for disposal. To find a possible clue of their high unusual mortality, their droppings were examined and were found to be acidic in nature indicating probably a healthy condition. Similar sporadic incidences where healthy vultures get unnoticed and could be a possible prey to the unnatural death should be a ground for further a possible revival strategy. An extensive unbiased work covering a wider area, involving all aspects in collaboration with various agencies is needed to find out the exact cause to avoid them from complete disappearance and revival either in wild or captive.
Vultures play an essential role in environmental health by scavenging meat from carcasses particularly in Asia (especially India), with large numbers of wild mammals, several unorganized carcass disposal sites and an extensively managed livestock. The white-backed vulture (Gyps bengalensis), and long-billed vulture (Gyps indicus) mainly represent the overall population of eight species of vultures in India. Others like Cinereous Vulture (Aegypius monachus) Bearded Vulture (Gypaetus barbatus) Himalayan Griffon (Gyps himalayensis) Eurasian Griffon (Gyps fulvus) Egyptian (Neophron percnopterus) King Vulture (Sarcogyps calvus) are either migratory or belong to other locations. Recently the long-billed vulture (Gyps indicus) was bifurcated into two distinct species, Indian vulture Gyps indicus indicus and slender-billed vulture Gyps indicus tenuirostris. India's both vultures Gyps bengalensis, and Gyps indicus very common until two-three years ago have suddenly & drastically declined by almost 95% (Prakash and Rahmani, 2000b Satheesan, 2000; Thiollay, 2000; Watson, 2000) and even 100% in some areas. They are now listed as critically endangered, presenting a whole range of threats, ranging from ecological to animal and human health. The absence of vultures will influence the numbers and distribution of other scavenging species, as seen at carcass disposal sites. The feral dog populations and crows have increased massively, posing many associated disease risks such as rabies, infections to poultry & domestic birds, etc.
In an unusual appearance, three vultures were noticed of at a buffalo carcass kept for disposal at Hiverkhedi village in the vicinity of Satpura forest area of Betul in Madhya Pradesh. On close observation their droppings were seen, collected and evaluated for the base content, as that was the only thing possible at that very moment. It was found to be of highly acidic nature, probably due to the nature of food consumed & their scavenging habits.
The vulture population (white-backed and long-billed Vultures) has declined all over the country, in protected as well as rural areas. There are several speculations and hypothesis about the cause of such unusual mortality. The most common is the head/neck drooping syndrome as reported in sick vultures in both species, where the birds appear sick and lethargic as they sit with limp necks and drooping heads, appear to be drowsy; the neck would fall limp and hang and in an attempt to appear wake up, would raise its head, and let it fall again. During the period of illness, however, the birds could fly short distances and even feed their young. They die and drop from their roosts, and remained suspended in the branches, or died on the nests; fledglings also were found dead in the nests (Prakash and Rahmani 2000a).
The adult to juvenile ratio has reduced to 9:1, probably suggesting a breeding failure. They lay a single egg in the mating season (October-March), and raise only one chick every year with a high breeding success. A low proportion of first year birds indicate probably due to direct and indirect effects of the high mortality (Prakash 1999). Causes of failure ranged from failure to lay eggs, failure of eggs to hatch, and death of young, each attributing to a deficiency of fitness in the breeding birds. Hunt for eggs or baby birds are getting to be hard.
Unattended cattle carcasses near nesting and roosting habitats rules out starvation and paucity of habitat as the cause of such huge mortality (Prakash 2001). Vulture carcasses show varying states of nutritional fitness, with substantial amounts of body fat (Cunningham et.al.2001). Large-scale deaths with renal failure during the summer months, was visible in necropsy as enteritis, renal and visceral gout (deposition of uric acid crystals) in the viscera (Cunningham 2000). Renal gout were occurring only a few hours prior to death as a consequence of some primary disease (possibly a response to terminal dehydration), and not the disease itself (Cunningham et.al.2001). Cases of visceral gout in adult vultures necropsies in Pakistan also signifies the same cause, and the presence of gout in nestlings and fledglings indicates a possible transmission from adults to progeny at the nest, could be by way of food brought back to the nest, or may be inherently present at nest sites (Virani 2001).
Poisoned carcasses: Administration of a poison (specially rodenticide zinc phosphide) to cattle so as to facilitate removal of the hides, and consumption of such carcasses. Carcasses have sporadically been poisoned throughout India to kill jackals, hyenas, wolves, leopards or tigers; invariably vultures are also killed.
A Pesticide Effect: The non-target effect of pesticides on vultures could be possible (Nair 1999). Toxic pesticides for birds include dieldrin and endrin (organochlorines), monocrotophos and parathion (organophosphates), and carbofuran as carbamates, which kill birds in a short time. At lower doses produce sublethal effects and birds eventually recover.
A New Environmental Chemical: A new environmental chemical derived from a non-agricultural use, a possible by-product of a pesticide or any other alternative, which might affect a larger area.
A New Disease: Transmission of a disease among birds might more readily occur in the crowded groups as in Gyps vultures that typically feed on larger carcasses. Also, an apparent failure to infect other species of vultures breeding in same areas like Egyptian vulture (Neophron percnopterus), and King vulture (Sarcogyps calvus) could be proved as in-species and in-generic differences in susceptibility, because both feed in small groups and are solitary feeders on smaller carcasses.
A Virus: Typically, viruses don't kill all members of host species, where more virulent mutants kill many individuals and the benign parent strain activates the immune system to protect the remainder. In case the virus came from another species and is appearing in vultures for the first time is the most possible hypotheses that account for the deaths of vultures and of their population decline. Also, a cytopathic virus isolation from the lung/spleen from one vulture, using 4 passages on chicken embryo fibroblasts, duck embryo fibroblasts, and peregrine embryo fibroblasts possibly provide some clue (Oaks et.al.2001).
A Prion: Prions are recently discovered proteinaceous infective particle causing a group of diseases known as transmissible spongiform encephalopathies (TSEs) responsible for causing Bovine spongiform encephalopathy (BSE) in cows, Ovine spongiform encephalopathy (scrapie) in sheep, Creutzfeldt-Jacob disease (CJD) in humans. All spreads by consuming meat products and are interlinked to each other. A great deal of work remains to be done in this aspect. Vultures possibly might have consumed an infected carcass, thereby getting infected.
Hot summer: Mass vulture deaths reported during the hot summer months (April-June) in parts of India and Pakistan could be the result of fledgling deaths also coinciding with a peak in "head-drooping" behavior occuring naturally soon after the fledging period coinciding these months, suggest an increasing ambient temperature in recent years and possibly other related stresses.
Mass killing: The Gyps Vulture species possess an immense size, and on occasion, a bird in flight may come in contact with aircraft and even endanger the flight pattern of passing aircraft, causing a grave risk for pilots and passengers. Air accidents due to vulture were reported few years back. A possible sabotage could not be ruled out where they might have been attracted at a particular place for mass killing, as vultures get attracted from far distances of up to 50kms in search of carcass.
Immune deficiency: Indiscriminate use of medicines (especially corticosteroids, performance enhancers, etc) in animals might have some role to play when ingested by vultures in the carcass of that animal. This may directly or indirectly damage their immune system and increase their susceptibility to disease.
Vultures also have cultural significance for the Parsee community. The ancient Parsee sectarian holds earth, air and water as sacred, and human body as evil. They do not bury, cremate or dispose of bodies, as this would defile those elements, instead scavengers devour their bodies. This system has worked well for at least 2000 years, and in Mumbai (formerly Bombay) in particular for 400 years. Over the time, the ritual got organized and 'Towers of Silence' were built, to place the bodies, which meant that only flying scavengers could utilize them, and so vultures became the main scavenger as they could quickly strip the flesh of the entire body in about half an hour and would fly out of the area. This method was considered sanitary, and avoids polluting their sacred elements. However, the once abundant vultures have declined to an extent that for about two years none have visited the Towers of Silence, posing serious problems for the Parsees. Now, in a way not to forsake their beliefs, the followers of Parse faith employ strong solar panels with huge reflectors, which concentrate radiation to desiccate and hasten the decomposition of their dead, thereby reducing it to nearly nothing within a few days.
Any birds now in captivity and apparently healthy should be regarded as priceless.
Vulture's ability to digest infected, rotting meat without impending any negative effects to its own health is a rather peculiar attribute and may prove useful in medical science. They are nature's own cleaning devices, removing infected carcasses from the environment before they pose the threat to other animals or humans. The dramatic vulture decline observed across India presents a whole range of ecological threats, by influencing the numbers and distribution of other scavenging species and ultimately to human and animal health. Increased feral dog populations have been reported allover in India posing many associated disease risks to humans and wildlife, especially diseases like rabies, etc. India already accounts for a very high incidence of rabies cases, and an absolute shortage of quality anti rabies vaccine in rural areas can aggravate the problem even further. Similarly increased crow populations at carcass site in vicinity of settlement areas pose a risk of infections to poultry, domesticated birds, avian & humans. Maggots do the scavenging job nowadays, adding to the stink making it difficult for people living nearby.
The decline of Indian vulture population has been very drastic and instant. Sick and dead vultures are also found in Nepal and Pakistan, indicating a potential to spread into other vultures across Europe, Africa and cause severe complications. There are several unanswered queries, indicated by deficient information, about the status, rate, extent, duration, area of mortalities, and breeding success of other Gyps vultures. Attempts should be made to protect vultures from extinction, and also to prevent a possible spread to other countries, with special emphasis:
Cunningham, A.A.;2000: Investigation of vulture mortality in India. Report of a visit to India (February-March 2000) RSPB and Bombay Natural History Society (BNHS).
Cunningham,A.A.; Prakash,V; Ghalsasi,G.R.; Pain, Deborah; 2001: Reports from the workshop on Indian gyps vultures. 4 th Eurasian congress on raptors, Sevilla, Spain
Galushin.V.M.; 2001: Reports from the workshop on Indian gyps vultures. 4 th Eurasian congress on raptors, Sevilla, Spain
Jemima Parry-Jones.2001. Reports from the workshop on Indian gyps vultures. 4 th Eurasian congress on raptors, Sevilla, Spain
Nair, A. 1999.What's Eating the Vultures? Down to Earth. 15 th January 1999 issue pp 29-39.
Oaks, J. Lindsay; Rideout, B.A.; Gilbert, M.; Watson, R.; Virani, M.; Khan. A.A.;2001: Reports from the workshop on Indian gyps vultures. 4 th Eurasian congress on raptors, Sevilla, Spain
Prakash V. ;1999: Status of vultures in Keoladeo National Park Bharatpur, Rajasthan, with special reference to population crash in Gyps species. Journal, Bombay Natural History Society, v.96, No 3, pp.365-378.
Prakash V & Rahmani, A.R.; 2000a: A brief report on the international seminar on vulture situation in India. Bombay Natural History Society, New Delhi 18 th to 20 th September 2000.
Prakash V. and Rahmani, A.R.;2000b: Notes about the decline of Indian vultures, with particular reference to Keoladeo National Park,Vulture News, v.41, pp.6-13.
Prakash V.;2001: Reports from the workshop on Indian gyps vultures. 4 th Eurasian congress on raptors, Sevilla, Spain
Satheesan S.M.;2000: The role of poisons in the Indian vulture population crash. Vulture News, v.42, pp.3-4.
Thiollay J.-M.;2000: Vultures in India. Vulture News, No 42, pp.36-38.
Virani M.;2001: Reports from the workshop on Indian gyps vultures. 4 th Eurasian congress on raptors, Sevilla, Spain
Watson R.;2000: Vultures in crisis. Peregrine Fund, Newsletter No 31, pp.20-21.
Government Veterinary Hospital, Khedi, Betul, M.P. India
E-mail: [email protected]