ORIGINAL PAPER Feeding responses of the red fox (Vulpes vulpes) to different wild rabbit (Oryctolagus cuniculus) densities: a regional approach Miguel Delibes-Mateos & Javier Fernandez de Simon & Rafael Villafuerte & Pablo Ferreras Received: 7 November 2006 / Revised: 27 April 2007 / Accepted: 30 April 2007 / Published online: 2 August 2007 # Springer-Verlag 2007 Abstract We investigate the feeding responses of the red fox (Vulpes vulpes) at a regional scale to different densities of European wild rabbit (Oryctolagus cuniculus) in central– southern Spain. Rabbit abundance indices were obtained in 86 localities during summer 2002. The diet of the fox was studied by analysis of 114 scats collected in 47 of these localities. The feeding response of the fox was examined by a representation of the dry weight percent of rabbit in the diet as a function of the abundance of rabbits; this used data only from those localities where at least 3 scats were collected (70 fox scats from 18 localities). We evaluated the relationship between rabbit abundance and the diversity of the diet of the fox. The feeding patterns of red foxes approximated to Holling’ s type III functional response, typical of opportunistic predators. There was a negative relationship between the diversity of the fox’ s diet and the abundance of rabbits. Therefore, the fox apparently behaves as a facultative predator, feeding on rabbits when they are abundant and shifting to other prey (and hence a more diverse diet) when rabbits are scarce. These findings are the first step towards understanding the potential role of red foxes in regulating rabbit populations in central–southern Spain. Keywords Diet analysis . Functional response . Predator–prey relationships . Spain Introduction The European wild rabbit (Oryctolagus cuniculus) is considered a keystone species in Iberian Mediterranean ecosystems (Delibes-Mateos et al. 2007) because it is the most important prey for vertebrate predators (Delibes and Hiraldo 1981) and because it also exerts a strong influence on the habitats of other species through consumption of vegetation, seed dispersal and burrowing (Soriguer 1986; Gómez-Sal et al. 1999; Dellafiore et al. 2006). Over the past 50 years, rabbit populations have suffered a dramatic reduction on the Iberian Peninsula, mainly as a result of the arrival of two viral diseases: myxomatosis in the 1950s (Muñoz 1960) and rabbit haemorrhagic disease (RHD) at the end of the 1980s (Villafuerte et al. 1995). Rabbit specialist predators such as the Iberian lynx (Lynx pardinus) or the Spanish imperial eagle (Aquila adalberti) have become seriously endangered mainly as a conse- quence of habitat fragmentation and the decline in rabbit numbers (Ferrer 2001; Palomares et al. 2001). The diminution of abundance of top predators together with habitat fragmentation have been cited as two of the factors that have led to an alarming increase in generalist species (Palomares et al. 1995; Storch et al. 2005; respectively). The red fox (Vulpes vulpes) is the most widespread generalist predator on the Iberian Peninsula (Blanco 1998) where, as in other Mediterranean areas, rabbits are the most Eur J Wildl Res (2008) 54:71–78 DOI 10.1007/s10344-007-0111-5 Communicated by W. Lutz M. Delibes-Mateos (*) : J. Fernandez de Simon : R. Villafuerte : P. Ferreras Instituto de Investigación en Recursos Cinegéticos, IREC (CSIC–UCLM–JCCM), Ronda de Toledo s/n, 13071 Ciudad Real, Spain e-mail: Miguel.Delibes@uclm.es J. Fernandez de Simon e-mail: Javier.Fernandez@uclm.es R. Villafuerte e-mail: Rafael.Villafuerte@uclm.es P. Ferreras e-mail: Pablo.Ferreras@uclm.es