Spatial organisation and feeding ecology of the American mink (Mustela vison) in a coastal habitat

Abstract

The American mink (Mustela vison Schreber) is the only introduced carnivore that has successfully colonised the British Isles. In the present study, the important problem of understanding which are the factors that limit or enhance their number has been addressed. A mink population (Mustela vison) inhabiting a coastal area of SW Scotland, was studied. The main purpose was to relate the spatial organisation of mink with spatial and temporal variations in the abundance and distribution of its prey, through the study of foraging strategies and habitat selection. Different scales of spatial organisation were considered. Foraging strategies (activity levels, habitat use, foraging behaviour) were found to vary over time and in areas with different habitat characteristics. The distribution and abundance of terrestrial prey was found to be important in determining such strategies, ultimately influencing mink densities. This observation supports the hypothesis of Clode and Macdonald (1995) on the influence of terrestrial prey on mink ability to disperse. Habitat selection of mink in the intertidal zone was studied here for the first time. Resident animals, which were foraging at low or mid tide, and within core areas were found to behave selectively, preferring areas with high prey abundance. In the intertidal zone, prey was most abundant in the lower shore, in areas without fresh water, and in areas with abundant and large rockpools. Mink showed preference for all these habitat characteristics. The nature of the substratum was also important in determining the abundance of prey out of rockpools. The results of this study are discussed in relation to limiting resources and competition with native carnivores. Finally a new home range estimator - the Density Circles method - was developed. This estimator is particularly suitable for describing home ranges presenting anomalous shapes, such as those found in mink.