Proximate and ultimate causes of dispersal in the Iberian lynx Lynx pardinus

Abstract

Most studies on the causes of animal dispersal focus on species of birds or small mammals, but there are few such studies on solitary carnivores. A complete picture of the causes of animal dispersal is not possible without considering cases on a representative set of animals. The Iberian lynx is a medium-size, solitary carnivore that inhabits metapopulations, where dispersal plays a prominent role. Between 1983 and 1998 we studied the proximate and ultimate causes of dispersal in Iberian lynx in the Don˜ ana metapopulation (southwestern Spain), based on radio-tracking of 49 individuals. Saturation of limited breeding areas in this small population leads to high dispersal rates in both sexes. Most lynxes dispersed from their natal area between 12 and 24 months of age. Males younger than 1 year old tended to disperse in a higher proportion than females of the same age. However, high dispersal rates for both sexes by the age of 2 years and the lack of differences in the dispersal distances do not support inbreeding avoidance as an ultimate cause of dispersal. Dispersal mainly started between January and June (24/29 cases), when most social interactions occur, which supports the social subordination hypothesis. Lynxes left the natal range at an earlier age from the local population with higher density, which supports intraspecific competition for resources as a cause for dispersal. However, prey seems not to be the limiting resource because dispersal mostly started during the season of increasing prey density, and individual probability of dispersal increases with prey density in the natal area. Dispersers suffered higher mortality than nondispersing lynxes of the same age, due mostly to anthropogenic causes. About half of the dispersers successfully settled in a territory at distances that differed between areas of origin, but not between sexes. Distances reached, shorter than those reported for other similar-size solitary felids, are limited by anthropogenic barriers that prevent connection with closer metapopulations. Key words: dispersal rates, lynxes, Lynx pardinus, resource competition, settlement, social subordination, survival