Poisoning causing the decline in South-East Asia’s largest vulture population

Abstract

SummaryCambodia supports populations of three Critically Endangered vulture species that are believed to have become isolated from the rest of the species’ global range. Until recently Cambodia’s vulture populations had remained stable. However a recent spike in the number of reports of the use of poisons in hunting practices suggests the need to re-evaluate the conservation situation in Cambodia. Population trend analysis showed that since 2010 populations of the White-rumped Vulture Gyps bengalensis and Red-headed Vulture Sarcogyps calvus have declined, while the Slender-billed Vulture Gyps tenuirostris may also have started to decline since 2013. These trends are supported by evidence of reduced nesting success. A survey of veterinary drug availability revealed that diclofenac, the non-steroid anti-inflammatory drug responsible for vulture declines in South Asia was not available for sale in any of the 74 pharmacies surveyed. However, a poisoned Slender-billed Vulture tested positive for carbofuran in toxicology tests. This provides the first evidence of a vulture mortality resulting from carbofuran in Cambodia. The findings suggest the urgent need to tackle use of carbamate pesticides in hunting. Proposed conservation actions are: a) prevention of poisoning through national bans on harmful carbamate pesticides and diclofenac and education campaigns to reduce demand and use; b) training of personnel in priority protected areas in detection and response to poisoning incidents; c) maintenance of a safe and reliable food source through vulture restaurants to ensure short-term survival, and d) protection and restoration of large areas of deciduous dipterocarp forests to enable long-term species recovery.

Simultaneous‐count models to estimate abundance from counts of unmarked individuals with imperfect detection

“…; Loveridge et al. ). These existing methods do not account for imperfect detection and so can be misleading (Guillera‐Arroita et al.…”

“…; Loveridge et al. ). We used count data from 2006–2014 from these simultaneous surveys at 6 sites for which data were available for all years: Chhaep Wildlife Sanctuary, Prey Siem Pang Kang Lech Wildlife Sanctuary, Phnom Prich Wildlife Sanctuary, Lomphat Wildlife Sanctuary, Srepok Wildlife Sanctuary, and at the Sesan River (Clements et al.…”

“…In northeastern Cambodia, animal carcasses are provided to vultures to prevent poisoning (Gilbert et al ) and to supplement food because wild ungulate populations are small (Loveridge et al. ). Carcass‐provision sites are surveyed simultaneously on 2 occasions/year 2 weeks apart in June, which is outside of the breeding season.…”

“…Several other sites were included in a few years (Loveridge et al. ), but because most occasions yielded few to no birds, we excluded them to simplify analyses. This is not likely to substantially affect the results.…”

“…We developed the SCM to estimate the abundance of the Cambodian populations of 3 critically endangered vultures: Red-headed Vulture (Sarcogyps calvus), Slenderbilled Vulture (Gyps tenuirostris), and White-rumped Vulture (Gyps bengalensis). In northeastern Cambodia, animal carcasses are provided to vultures to prevent poisoning (Gilbert et al 2007) and to supplement food because wild ungulate populations are small (Loveridge et al 2018). Carcass-provision sites are surveyed simultaneously on 2 occasions/year 2 weeks apart in June, which is outside of the breeding season.…”