Predation upon European Rabbits and Their Use of Open and Closed Patches in Mediterranean Habitats

Abstract

Animal use of habitats and patches may vary in relation to foraging profitability and predation risk (MacArthur and Pianka 1966). Around this idea, Jaksic and Soriguer (1981) made a suggestive comparison of predation upon and patterns of habitat use by European rabbit, Oryctolagus cuniculus, in Mediterranean habitats of southern Spain (the area of origin of species) and central Chile (where it had been introduced). The main conclusions of their work were: 1) predators in central Chile pass introduced rabbits by and consequently non-predated rabbits select to feed in more profitable open patches; and 2) conversely, predators in southern Spain regularly hunt native rabbits, which are forced to keep themselves close to protective vegetation avoiding open patches. To reach these conclusions, they reviewed literature on diets of predator assemblages of both places (central Chile and southern Spain) and counted rabbit pellets in different habitat patches varying in shrub cover. Jaksic and Soriguer (hereafter J&S) explained their finding that rabbits were a small component of diet of central Chile predators on their lack of behavioural adjustment (inefficiency) to hunt a recently introduced prey. Spanish data would support this idea, as rabbits and predators have co-evolved in this area and therefore latter would be efficient at hunting rabbits. On other hand, as rabbits in Chile were not preyed upon, they would behave as being predator-free, using open shrub areas where herb availability would be higher. On contrary, rabbits in Spain would select close vegetation patches where shrubs could provide them with adequate shelters (i.e. nearby shrubs would be more important than abundant food for rabbit survival). The results of J&S were so clear and presented so elegantly that in last fifteen years the Chilean and Spanish rabbit cases (i.e. reported differences in predation pressure upon rabbits in Chile and Spain and associated behavioural change in habitat use by rabbits) have been widely accepted and thus invoked by scientific community (e.g. Simonetti and Fuentes 1982, Newsome et al. 1989, Trout and Tittensor 1989, Jaksic and Fuentes 1991, Kolb 1991, Ferrer 1993). Nevertheless, fine-tuning co-evolutionary adjustment between most vertebrate predators and their prey has not been proved until now. Available data suggest that vertebrate predators are usually quite flexible and adaptable in prey selection, whether they are native predators hunting for introduced prey (e.g. Myers et al. 1994) or are introduced predators hunting for native prey (e.g. Fitzgerald 1988). On other hand, it is difficult to believe that locally abundant Spanish rabbits give up rich food of open pastures, as it has been stated that rabbits need grassy areas in Mediterranean habitats of Spain (Rogers and Myers 1979). We think it is important to reanalyse and discuss widely accepted conclusions of J&S in light of newly available information. Specifically, we will try to demonstrate that 1) Chilean predators may hunt for rabbits more frequently than J&S reported, 2) Spanish rabbits use open areas more often than J&S found, and 3) use of open areas by rabbits (at least in Spain) may be enhanced by presence of warrens, which are used as shelters.