Mountain Vultures: Alpine Ecology, Carrion Roles, and Conservation

Biome 10, montane grasslands and shrublands (alpine or montane climate), exists in the Asian Himalayan mountains and the South American Andes. The montane grasslands and shrublands above the tree line (the maximum height at which trees will grow, based on the temperature) are termed alpine tundra. The montane grasslands and shrublands below the tree line are termed subalpine and montane grasslands and shrublands. Stunted subalpine forests occur just below the tree line, as cold, windy conditions and poor soils are factors for small, twisted, slow-growing trees. Large areas of montane grasslands and shrublands are in the Neotropic Paramo of the Andes mountains and the montane steppes of the Tibetan plateau.

The Tibetan plateau has been described as the largest and highest highland in the world. The landcover is principally meadow, alpine shrub, and primitive forests. The main human livelihood is livestock raising, especially in the meadows. There are also several large wild ungulates; yak (Bos grunniens Linnaeus, 1766), Tibetan ass (Equus kiang Moorcroft, 1841) and Tibetan antelope (Pantholops hodgsonii Abel, 1826). In the Alpine shrub habitat human populations are dense, with farming in the riverine lowlands and livestock rearing in the nearby mountains. There is forest habitat on eastern and southeastern fringes (Lu et al. 2009).

Himalayan Griffon vultures, 'the only high-elevation Gyps species', have been documented in the plateau. The meadow supported the largest population of Griffon vultures, (71%), followed by the alpine shrub (23%) and forest (6%). Carcasses in the forest and shrubbery may be overlooked by foraging vultures and the vultures' habitat preferences are believed to be due to the differences in livestock availability in the three habitat types. Most of the livestock grazed in the meadows, due to the 'greater visibility of approaching terrestrial predators' (Lu et al. 2009: 171; see also Cramp and Simmons 1980; Gavashelishvili and McGrady 2006; Bose and Sarrazin 2007, for a discussion on the importance of prey size and open landcover for vultures). The vultures' diet was principally Domestic yaks (64%), horses, donkeys and also wild ungulates (1%) and human corpses (2%) (Lu et al. 2008). Considering the diet of the vultures was principally livestock, it is uncertain what the population density of the vultures would be in a natural environment. The human corpses were an aspect of the Tibetan culture, termed sky burials, where human bodies were cut up, bones broken into fragments and given to the vultures at certain sites. Cinereous and Bearded vultures were recorded with Himalayan Griffons at carcasses. The latter bird dominated the others in numbers and access to carcasses. Other scavengers were feral dogs and ravens. In some cases the feral dogs were able to exclude the vultures from the carcass.

Another species that occurs in montane environments is the Bearded Vulture. This species occurs in the mountainous regions from Europe (the Pyrenees, the Alps, the Caucasus region), Asia and Africa. The range in Asia includes the Zagros Mountains, the Alborzs, the Altai Mountains, the Himalayas, western and central China, Israel and the Arabian Peninsula. The African range includes the Atlas Mountains, the Ethiopian Highlands and the Drakensberg of South Africa (Ferguson-Lees and Christie 2001).

The Bearded Vulture favors alpine meadows, grassland and inselbergs with cliffs, crags, precipices, canyons and gorges, especially where human populations are low or absent, and predators such as Golden Eagles and wolves provide the carcasses from which the bones are derived.

A study by Hirzel et al. (2004) documented environmental preferences among the reintroduced Bearded vultures in the European Alps from which they became extinct about 100 years ago. The introduction programme began in 1986 and by 2003, 121 birds had been released from captivity. Factors for the species presence were the presence of ibex and the limestone substrates in the area. Ibex forage in Alpine ecosystems with meadows and grasses. The limestone landscapes, compared to silicate substrates, provided better ground for bone breaking and food storage and also better thermal conditions for soaring. The study concluded that population reintroductions would be successful if birds were released in areas with large limestone massifs. Another study by Bogliani et al. (2011) in the Italian Alps found that Bearded Vultures foraged at higher altitudes during warmer months, and at lower altitudes during snowfall. This followed the presence of commonest ungulates of the park, the alpine ibex (Capra ibex) and the alpine chamois (Rupicapra rupicapra Linnaeus, 1758), their main food. Habitats included vegetated cliffs and screes, forest-scrub mosaics, and agriculturaland to a lesser extent bare rocks and deciduous forests.

The Andean condor in South America has a similar lifestyle. This species prefers high montane canyons and peaks and forages in open grasslands, while communally on inaccessible cliffs and rocky crevices and outcrops. This species feeds off the carcasses of llamas (Lama glama, Linnaeus 1758), alpacas (Vicugna pacos, Linnaeus 1758), guanacos (Lama guanicoe, Muller 1776), rheas (Rhea americana, Linnaeus 1758) and armadillos (Dasypodidae spp., Gray 1821). More recently it has been recorded feeding on domestic livestock (cattle, horses, donkeys, mules, sheep, pigs, goats and dogs) and introduced species such as boars (Sus scrofa, Linnaeus 1758) and red deer (Cervus elaphus, Linnaeus 1758) (Newton 1990; del Hoyo et al. 1994; Swaringen et al. 1995). All of these are found in high and lowland meadows and pastures (Newton 1990; del Hoyo et al. 1994; Swaringen et al. 1995). When the California Condor was common, it also favored similar terrain, namely the temperate and subtropical prairies and grasslands of western North America, and also the Rocky mountain ranges of that area (Koford 1953).