Can predators regulate wild Rabbit Oryctolagus cuniculus population density in England and Wales?

Abstract

ABSTRACTPredation has usually been interpreted as being a compensatory mortality factor, removing only the doomed surplus. The literature on the wild Rabbit Oryctolagus cuniculus L. is reviewed to collate counter‐evidence for a regulating influence of predation. This evidence is almost entirely circumstantial, not experimental. Predation has been reported to extend the length of time Rabbit populations remain low following a significant reduction of Rabbits by some other agent. Rabbit populations have been shown to increase very rapidly when predator density has suddenly been reduced. It has been suggested that predators affect the spread and dispersion of Rabbits both at the geographical and local levels. Predation has not, however, been shown to have an important influence at high Rabbit densities. Thus, its role can be that of a limiting factor rather than a density‐dependent regulatory mortality factor.The concept of predator pressure is presented and discussed, pointing out that there is currently no standard technique used for its measurement.Further evidence on the importance of predation is presented from four recent studies in England and Wales that relate, by association, the distribution and abundance of local Rabbit populations to the local attitude towards predators. Rabbits were found to be significantly more widespread and abundant where predators were removed (not restricted to keepered game estates) or at low density, than when predators were undisturbed or at a high density. The significance of these results is discussed.The circumstantial and corroborative evidence leads strongly to the conclusion that predator pressure can act as an additive rather than compensatory mortality factor in some circumstances, and can thus be a potential regulating factor. Predation is more likely to be a limiting factor at low Rabbit density however, since a density‐dependent relationship has not been demonstrated throughout the range of Rabbit densities that occur. This requires experimental demonstration to determine the threshold pressure below which predation becomes limiting. If so, reductions in Rabbit populations by short‐term control operations could allow natural predation to help maintain low Rabbit densities for several years in some habitats. Conversely, the implications for Rabbit populations and thus crop damage resulting from predator control (e.g. in game management regimes) should be appreciated.