Dietary shifts in two vultures after the demise of supplementary feeding stations: consequences of the EU sanitary legislation

Abstract

Among vertebrates, specialization in scavenging has appeared only in "true" Gyps vultures, which usually base their diet almost exclusively on carcasses of medium and large-sized mammals, whereas all other scavengers rely on broader ranges of prey. The availability of food for scavengers in Western Europe has not been limited during recent decades permitting the existence and growth of huge vulture populations. From 2000 onwards, however, EU sanitary legislation has progressively limited the abandonment of dead animals in the field resulting in a sudden reduction of food availability with unknown ecological and conservation consequences. Here, we examine the dietary response of a tandem of carrion eaters, the griffon vulture (Gyps fulvus) and the Egyptian vulture (Neophron percnopterus), showing different degrees of dietary specialization. Our results showed that after the reduction in numbers of supplementary feeding stations (vulture restaurants) the niche breadth of the griffon vulture has broadened and now includes significant amounts of wild rabbits (Oryctolagus cuniculus) and garbage. The diet of the Egyptian vulture, on the contrary, did not vary substantially. The diet overlap showed patterns probably conditioned by interspecific competition and the progressive exploitation of unpredictable carcasses. On a short-term scale, consequences for smaller scavengers could be negative due to the monopolization of resources by the dominant and much more abundant griffon vulture, however in the long-term all guild species would benefit from the exploitation of unpredictable carcasses, which could enhance the possibilities of coexistence.

Manipulating size, amount and appearance of food inputs to optimize supplementary feeding programs for European vultures

“…The fact that this study was performed at fixed feeding locations could enhance this effect and partially bias the conclusions with regards to unmanaged situations (Monsarrat et al, 2013). In this sense, the most specialist and territorial vultures balance this negative situation and optimize carrion ingestion with improved detection capabilities of small carcasses from a wider range of wildlife species randomly distributed in the field (Ceballos and Donázar, 1990;Margalida et al, 2009;Donázar et al, 2010).…”

“…Finally, the Egyptian vulture optimized intake efficiency when the input consisted of remains formed by meat, entrails and bones. Due to its soft texture, this type of input would lead to small pieces and scraps not initially hoarded by the griffon vulture (Ceballos and Donázar, 1990;Donázar et al, 2010).…”

EU Sanitary Regulation on Livestock Disposal: Implications for the Diet of Wolves

“…As a result of these changes, wolf population in Galicia has become highly dependent on roe deer and wild pony population. Previous studies have indicated that these same sanitary measures have affected avian scavenger populations and ecology (Camiña and Montelío 2006;Donázar et al 2010;Margalida et al 2010;Camiña and Yosef 2012).…”

“…The changes in the livestock carcass disposal systems from 2000 onwards first opened the debate on how these new regulations might affect the ecology and conservation of endangered populations of scavenging birds (Tella 2001). As a consequence, several studies were conducted on the impact of those regulations on vultures (Camiña and Montelío 2006;Donázar et al 2010;Camiña and Yosef 2012). Wolves were also considered potentially vulnerable to those regulatory changes which restricted carrion availability (Barrientos et al 2005;Blanco and Cortés 2005).…”

Top Scavengers in a Wilder Europe

“…Species managed by supplementary feeding include: the California Condor ( Gymnogyps californianus) in Western North America; the King Vulture ( Sacorramphus papa) in Belize; and the Cape Vulture ( Gyps coprotheres) and bearded vulture in Southern Africa (Wilbur and Jackson 1983;Houston 1987;Brown 1990;Mundy et al 1992). In Eurasia, vulture restaurants have mainly targeted populations of bearded, Egyptian, griffon, and cinereous vultures (Donázar 1993;Donázar et al 2009aDonázar et al , 2010Cortés-Avizanda et al 2010;Fig. 5.4).…”