ABSTRACT
Several studies have shown that the diet of the North American mink can vary according to habitat, season and sex (Gerell, 1967;Akande, 1972; Day & Linn, 1972; Birks & Dunstone, 1985; Dunstone & Birks, 1987). It is clear that at times, particularly in autumn and winter, both male and female mink may obtain over 50 % of their food (as fish and crustaceans) from an aquatic environment. Thus, mink will readily take to water and dive to capture prey despite the fact that they possess very few anatomical adaptations which enhance their ability to hunt underwater. Indeed, the unusually high resting metabolic rate of mustelids (Iversen, 1972) and the high energetic cost of transport during surface swimming (Williams, 1983) argue against the successful use of a diving foraging strategy. Brown & Lasiewski (1972) proposed that the adaptive advantage of the elongated body shape of mink (which is energetically expensive because of high rates of heat loss as a result of the high surface area to body volume ratio) lies in the increased ability to capture prey in confined spaces (e.g. lagomorphs in their burrows; Dunstone & Birks, 1987). Perhaps an enhanced ability to capture fish and crustaceans in underwater hides (e.g. Dunstone, 1978) compensates for their presumed locomotory inefficiency underwater.
