Dropping dead: causes and consequences of vulture population declines worldwide

Abstract

Vultures are nature's most successful scavengers, and they provide an array of ecological, economic, and cultural services. As the only known obligate scavengers, vultures are uniquely adapted to a scavenging lifestyle. Vultures' unique adaptations include soaring flight, keen eyesight, and extremely low pH levels in their stomachs. Presently, 14 of 23 (61%) vulture species worldwide are threatened with extinction, and the most rapid declines have occurred in the vulture-rich regions of Asia and Africa. The reasons for the population declines are varied, but poisoning or human persecution, or both, feature in the list of nearly every declining species. Deliberate poisoning of carnivores is likely the most widespread cause of vulture poisoning. In Asia, Gyps vultures have declined by >95% due to poisoning by the veterinary drug diclofenac, which was banned by regional governments in 2006. Human persecution of vultures has occurred for centuries, and shooting and deliberate poisoning are the most widely practiced activities. Ecological consequences of vulture declines include changes in community composition of scavengers at carcasses and an increased potential for disease transmission between mammalian scavengers at carcasses. There have been cultural and economic costs of vulture declines as well, particularly in Asia. In the wake of catastrophic vulture declines in Asia, regional governments, the international scientific and donor communities, and the media have given the crisis substantial attention. Even though the Asian vulture crisis focused attention on the plight of vultures worldwide, the situation for African vultures has received relatively little attention especially given the similar levels of population decline. While the Asian crisis has been largely linked to poisoning by diclofenac, vulture population declines in Africa have numerous causes, which have made conserving existing populations more difficult. And in Africa there has been little government support to conserve vultures despite mounting evidence of the major threats. In other regions with successful vulture conservation programs, a common theme is a huge investment of financial resources and highly skilled personnel, as well as political will and community support.

Environmental drivers of variability in the movement ecology of turkey vultures (Cathartes aura) in North and South America

“…The turkey vulture is the world's most abundant and widely distributed obligate avian scavenger, and appears to be adapting to or pre-adapted to human-caused changes in the environment better than its Old World counterparts, many of whom are facing steep population declines [25]. The species' global population, which exceeds five million individuals, appears to be increasing.…”

“…Alternatively, decreases in primary productivity driven by drought may increase the need for larger home ranges leading to increased competition, which may reduce the population density. That said, the enormous variability we have uncovered in the movement ecology of this species suggests that it is likely to do well in the face of global change, and that unless other human-related threats [25], including environmental toxicants or increased direct human persecution, intervene, the species is likely to remain widespread and abundant across much of its current range. Whether other partial migrants will fare as well is likely to depend on the extent of variability in their migration syndromes.…”

ENTERIC PATHOGENS AND ANTIMICROBIAL RESISTANCE IN TURKEY VULTURES (CATHARTES AURA) FEEDING AT THE WILDLIFE–LIVESTOCK INTERFACE

“…9 Regular consumption of livestock remains places scavenging birds at heightened risk of exposure to veterinary drug residues, as evidenced by vulture die-offs from diclofenac toxicity on the Indian subcontinent. 9 A Canadian study found that wildlife residing near livestock operations exhibited greater antimicrobial resistance relative to other habitats.…”

Two decades of cumulative impacts to survivorship of endangered California condors in California

“…Increasing independence in this population has contributed to recent increases in lead-related mortality, which are also likely evident from improved detection in the post-ban period with fewer deaths from undetermined causes. Similar to other vulture populations experiencing declines worldwide (Fisher et al, 2006;Ogada et al, 2012;Shultz et al, 2004), California condors are susceptible to large-scale poisoning events as a result of communal foraging behavior that puts several individuals at risk of exposure to a single contaminated carcass (Ogada et al, 2012). Progress toward recovery is not sustainable if the level of management required to ameliorate the threat of lead poisoning for the condor population remains the same, as the majority of investment has been put forth to reducing mortality rates rather than improving the viability of the reintroduced populations (Walters et al, 2010).…”