Estimation of Population Density of Bearded Vultures Using Line-Transect Distance Sampling and Identification of Perceived Threats In the Annapurna Himalaya Range of Nepal

Abstract

Bearded Vulture (Gypaetus barbatus) populations are declining across most of the species' global range. We studied Bearded Vultures in the Annapurna Himalaya Range of Nepal using line-transect distance sampling, and quantified the perceptions of threats to the species by interviewing local people in two different elevational areas. We recorded 35 Bearded Vultures (26 adults, 5 non-adults, 4 birds of unknown age) along a 168-km transect, yielding an encounter rate of 0.21 individuals/km. Based on distance sampling, we estimated a vulture density of 0.184 individuals/km2 in the study area. Local people in the two areas perceived population status and threats to the Bearded Vulture differently. At the lower elevational range (1398–2108 m), people perceived that the vulture population is declining and that the major threats are food shortage and secondary poisoning via the use of poisons by livestock herders to kill mammalian carnivores. At higher elevations (2538–3813 m), people perceived that the vulture population is stable with no lack of food; there also was a larger prevalence of the use of vulture body parts for traditional medicine in this area. Our study suggests that unintentional poisoning, food shortage, and use of vulture body parts are the primary threats to the Bearded Vulture in the Annapurna Himalaya Range of Nepal.