Vulture Crisis: Feeding Ecology and Conservation Coverage
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.
A Griffon vulture in flight. Photo: Udayan Borthakur
Vultures' visits to the carcasses are controlled by three major factors- visibility, take-off space and safety. When even one of these factors is compromised, Vultures do not feed on a carcass 1974). Unfortunately, around 14 out of 23 Vulture species are on the verge of extinction worldwide largely because of their natural food habits. The carrion eater which has for centuries cleaned up dead animals now faces maximum exposer of fatal drugs. Deliberate poisoning of carnivore and other domesticated animal, bio-magnification through the domestic animal, road killing are the mounting threats. However, 10 years after the discovery of the lethal effect of non-steroidal anti-inflammatory drug (NSAID), primarily Diclofenac theory has gained wide coverage. Diclofenac, has been banned by the Government of India in the use of veterinary sector since 11t May 2006. When feeding on the carcass of an animal, which had died within 72 hours after being treated with Diclofenac, the Vulture too dies of visceral gout (Taggart et al. 2006). The uric acid gets deposited kidney failure even at a very low dose (Oak et al. 2004).
Unfortunately, infiltration of human use Diclofenac has been widely reported in veterinary usages in many parts of India, inspite of the ban. Large vials (300ml) of the drug are widely available in market and infiltration to veterinary sector is commonplace. It is critical that the law be properly enforced to tackle this issue. After the ban on Diclofenac, efforts on searching for an alternative drug finally manifested 'Meloxicam'. It has been tested on over 700 birds from 60 species with no fatalities (Cuthbert et al. 2007). It is also as effective in the treatment of animals as Diclofenac.
While assessing the conservation effort over the years, Cuthbert et al. (2011) claimed that the Diclofenac prevalence level has been declined to half due to the ban on the NSAID. A domesticated ungulate carcass survey was conducted in 9 states of India (Cuthbert et al. (2011). Unfortunately Assam and North-east India is still to be covered by this study. It needs to be pointed out that the most fragile species in terms of population among the Gyps Vulture species, the Slender-billed Vulture, is mostly found in Assam. Irrespective of the conservation coverage, biasness in the formulation of research plans, with spatial aggregation, is also considered as a major weakness in Vulture conservation initiatives. On the other hand most of these studies are monotypic and societal diversity in culture, life-style, socio-economic status and food habits of different regions is barely considered. This is noteworthy as the feeding ecology of vultures is principally intertwined with human society.
The latest episodes of mass Vulture deaths in Assam occurred in Demo, Sivasagar and in Dhola, Tinsukia districts where around 100 Vultures died because of deliberate poisoning. An insecticide (Furadon) was suspected as the primary cause of death, since the birds died immediately after feeding on a carcass. On the otherhand, Diclofenac poisoning is slow and Vultures exhibit "neck-dropping' syndrome for around 7-15 days before death. Few sporadic studies done in the recent past claimed other factors like Malaria parasite (Poharkaret al. 2009), E-coli (Mora et al. 2014), eco-transformation (Saran and Purohit, 2012) as additional threats. Khatriet al. 2012) believed that the Diclofenac is not lethal to the Eurasian Griffon.
The Vulture conservation movement thrusts towards alternatives of NSAIDS and captive breeding; however the additional causes of Vulture deaths cannot be disregarded. Instead of focusing on a single pitfall, the varied causes differing from region to region should be taken into consideration for better conservation prospects. In Assam, deliberate poisoning, felling of nesting trees due to superstitions, food scarcity leading to unprecedented Vulture population decline, which cannot be overlooked. The idea of 'Vulture restaurant', where carrion is deposited for Vultures to feed on, has been quite successful in neighboring country Nepal. This cost effective theory not only revives the population to some extent, but also creates more awareness among the general people. It encourages them to donate food to wild population, to study in an in-situ environment, enhances eco-tourism, and creates a symbiotic link with cattle owners. It also acts to deter veterinary infiltration of Diclofenac, especially among communities that depend on cattle farming. The first Vulture restaurant was established in Namibia in 1987. The "Jatayu restaurant" in Nawalparasi district of Nepal has received much appreciation and it was reported that the population of White-backed Vulture increased near the restaurant (BCN2009). Conversely in India, the idea is yet to find acceptance among the major fraction of the conservation stakeholders.
The 'International Vulture Awareness Day' is celebrated every year on the first Saturday in the month of September. But this is not enough. Integrated research and awareness initiatives combined with effective political crucial to safeguard the Vultures intervention are (Balmford 2013). The significance of Vulture decline needs to be disseminated through the media, educational syllabus and mass awareness campaigns, especially in those areas where the breeding colonies are located. Lack of proper scientific investigation creates an information gap with many unanswered questions. A case in point is, a small breeding population of Vultures in Majuli existed till 2008 but the birds disappeared all of a sudden. They might have shifted to a new do not have any evidence of this. Similarly, in Tinsukia and Dibrugarh districts, many Vulture colonies may have shifted locations but in absence of proper scientific evidence this too could not be established. We are having information of population trends, breeding success and other ecological parameters for vultures which is urgent for their conservation.
Fondly called the 'king of the sky', Vultures provide usa wide array of ecological and economic services and now it is our turn to fight for their existence. It is our turn to fight for their existence. It is our duty to ensure that their food is free from lethal agents and they are allowed to fly free.
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About the Author:
Dr. Dipankar Lahkar is working as Manager in Tiger Research and Conservation Division, Aaranyak. He has also authored a book titled "Vultures in Captivity", published by Laplambert, Germany.