Abstract
BackgroundThe reduction in the amount of food available for European avian scavengers as a consequence of restrictive public health policies is a concern for managers and conservationists. Since 2002, the application of several sanitary regulations has limited the availability of feeding resources provided by domestic carcasses, but theoretical studies assessing whether the availability of food resources provided by wild ungulates are enough to cover energetic requirements are lacking.Methodology/FindingsWe assessed food provided by a wild ungulate population in two areas of NE Spain inhabited by three vulture species and developed a P System computational model to assess the effects of the carrion resources provided on their population dynamics. We compared the real population trend with to a hypothetical scenario in which only food provided by wild ungulates was available. Simulation testing of the model suggests that wild ungulates constitute an important food resource in the Pyrenees and the vulture population inhabiting this area could grow if only the food provided by wild ungulates would be available. On the contrary, in the Pre-Pyrenees there is insufficient food to cover the energy requirements of avian scavenger guilds, declining sharply if biomass from domestic animals would not be available.Conclusions/SignificanceOur results suggest that public health legislation can modify scavenger population trends if a large number of domestic ungulate carcasses disappear from the mountains. In this case, food provided by wild ungulates could be not enough and supplementary feeding could be necessary if other alternative food resources are not available (i.e. the reintroduction of wild ungulates), preferably in European Mediterranean scenarios sharing similar and socio-economic conditions where there are low densities of wild ungulates. Managers should anticipate the conservation actions required by assessing food availability and the possible scenarios in order to make the most suitable decisions.
Highlights
The crises among avian scavengers in the Old World during the last few years of the 20th century have revealed the sensitivity of vulture populations to the sudden appearance of non-natural mortality factors
In addition to this, one of the limiting factors that has generated the greatest amount of debate in recent years, and may the most worrying for the conservation of European vultures, is the impact that restrictive public health policies may have on European avian scavenger populations in general, and on Spanish populations in particular, as a result of the reduction in the amount of food available to these birds [13,14]
Food provided by wild ungulates in the Pyrenean region We found significant differences between the bone remains provided by the six ungulate species present in the Pyrenean region (F = 10.54, d.f. = 5, 84, P,0.0001), with the Pyrenean chamois Rupicapra pyrenaica and red deer Cervus elaphus being the species that provided significantly more animal biomass than the remaining species (Duncan test, P,0.05, Figures 1 and 2)
Summary
The crises among avian scavengers in the Old World during the last few years of the 20th century have revealed the sensitivity of vulture populations to the sudden appearance of non-natural mortality factors. European vultures have been affected and, in recent years, the status of their populations has become precarious, with the appearance and increases of non-natural mortality factors that may have an impact on their dynamics. During the first decade of the 21st century, following the outbreak of bovine spongiform encephalopathy, in Europe most carcasses of domestic ungulates were removed, limiting food resources for avian scavengers [13,14,15,16] The application of this public health legislation contradicted environmental conservation policies, preventing avian scavengers from obtaining the most important food resources (i.e. domestic ungulates), on which their diet has been based for centuries. Since 2002, the application of several sanitary regulations has limited the availability of feeding resources provided by domestic carcasses, but theoretical studies assessing whether the availability of food resources provided by wild ungulates are enough to cover energetic requirements are lacking
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