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Keywords:

  • Bonelli’s eagle;
  • conservation;
  • diet;
  • emerging infectious disease;
  • Hieraaetus fasciatus;
  • rabbit;
  • rabbit haemorrhagic disease;
  • spatial patterns;
  • temporal shifts;
  • western Europe

Abstract

Aim  To explore the influence of an emerging infectious disease (EID) affecting a prey species on the spatial patterns and temporal shifts in the diet of a predator over a large geographical scale. We reviewed studies on the diet of Bonelli’s eagles (Hieraaetus fasciatus) in order to determine the repercussions of the reduction in the density of its main prey, the rabbit (Oryctolagus cuniculus), caused by outbreaks of rabbit haemorrhagic disease (RHD) since 1988.

Location  Western continental Europe.

Methods  We compiled published and unpublished information on the diet of breeding Bonelli’s eagles from Portugal, Spain and France for a 39-year study period (1968–2006). Nonparametric tests were used in order to analyse temporal shifts in diet composition and trophic diversity (H′) between the periods of ‘high’ (before outbreak of RHD) and ‘low’ rabbit density (after outbreak of RHD). A combination of hierarchical agglomerative clustering and non-metric multidimensional scaling (NMDS) analyses were used to test for the existence of geographical patterns in the diet of Bonelli’s eagles in each period.

Results  The diet of the Bonelli’s eagle consisted of rabbit (28.5%), pigeons (24.0%), partridges (15.3%), ‘other birds’ (11.6%), ‘other mammals’ (7.1%), corvids (7.0%), and herptiles (6.4%). However, RHD had large consequences for its feeding ecology: the consumption of rabbits decreased by one-third after the outbreak of RHD. Conversely, trophic diversity (H′) increased after outbreak of RHD. At the same time, the analyses showed clear geographical patterns in the diet of the Bonelli’s eagle before, but not after, RHD outbreak.

Main conclusions  Geographical patterns in the diet of the Bonelli’s eagle in western Europe seem to be driven mainly by spatio-temporal variation in the abundance of rabbits and, to a lesser extent, by the local (territorial) environmental features conditioning the presence and density of alternative prey species. We show that an EID can disrupt predator–prey relationships at large spatial and temporal scales through a severe decline in the population of the main prey species. Hence we argue that strict guidelines should be drawn up to prevent human-aided dissemination of ‘pathogen pollution’, which can threaten wildlife not only at the population and species level but also at the community and ecosystem scale.