Text by Dr. Dipankar Lahkar
A Critically Endangered Slender-billed Vulture. Photo: Udayan Borthakur
A few decades ago Vultures were a common sight in India and North East. Not anymore! Vultures in India are at present facing a cataclysmic decline in numbers, due to a number of human caused reasons, which has directly affected the food source. This alarming decline has caused serious ecological imbalance. Without Vultures, the carcass is laid exposed for many days. The rotting carcass accumulates lethal pathogens such as anthrax posing serious threat to human and other wildlife. In the absence of Vultures, feral dogs are growing in population, which spread rabies, distemper and parvovirus creating an enormous threat to the human society. According to the World Health Organization (in 2003), the occurrence of rabies death in India is highest among Asian countries.
Feeding habit and feeding behavior exhibit the feeding ecology which is one of the prerequisite elements for the survival of a species in any form of ecosystem or in a region. Dietary habits are critical not only to determine the nutritional requirements of the species but also to understand how distribution of food resources determines population abundance or density, local distribution and social interactions (Oats 1987). Further understanding ecological requirements in terms of food and space which can lead to significant conservation of Vultures.
The Vulture belongs to the Order Falconiformes and Family Accipitridae. Sixteen species of Vultures are found globally (Lees and Devids 2001) of which nine are found in the Indian sub-continent. The Vultures are scavengers and feed exclusively on carcasses. The Indian species have different food preferences shared over a single carcass that allows them to coexist in a common pedestal. For example, in Keoladeo National Park, Rajasthan, 7 species of Vultures were reported as feeding together from the same carcass. In case of birds, the body morphology and physiology exhibit the feeding habits to a large extent. The Egyptian Vulture, smallest among the Indian species, has a thin bill and a light skull and it prefers tendons and ligaments of a carcass. They have also been known to feed upon carcasses of human babies in Egypt (Kennedy 1874) and Ostrich eggs by ingeniously throwing stones at them to break open the shell (Goodall 1970). They also consume scat of carnivores and maggots found in buffalo dung. Red-headed or King Vulture and Cinereous Vultures have powerful beaks enabling them to feed on the skin and tough parts. These birds slit open the carcass, which make it easier for the other Vultures to feed on the soft flesh. Lammergeier Vultures feed on bones and bone marrow by dropping the bone on rocks to break them open (Newton 1979). The White-backed, Long-billed, Slender-billed Vultures belong to a genus Gyps, are large with heavy bills and long necks which enables tearing off soft flesh especially viscera organs (Kruuk 1967). The flock size is also an important parameter as Vultures need to together to defend their carcass from other animals.