Indigenous to moist organic soils bordering on creeks, lakes

and wetlands, the star-nosed mole (Condylura cristata) is one of the most distinctive mammals anywhere on Earth. Extensively distributed throughout eastern Canada and northeastern USA, star-nosed moles are reported to inhabit subarctic regions as far north as the fifty-fifth parallel (Peterson and Yates, 1980). Active year-round, C. cristata is chronically exposed to low ambient temperatures that may persist for six or more months a year over much of the species’ range. In fact, star-nosed moles have been observed actively tunnelling through snow (Tenny, 1871; Merriam, 1884a) and even swimming and diving in ice-covered streams during winter (Merriam, 1884b; Seton, 1909; Hamilton, 1931). The small body size (40–70 g), northern distribution and conspicuous semi-aquatic habits of C. cristata (Peterson and Yates, 1980) suggest that this species may be among the most thermally challenged members of the Order Insectivora. Considering the varied and potentially stressful thermal environments encountered by C. cristata in nature, surprisingly little data exist on the energetics and thermal biology of these peculiar animals, either in air or in water (Campbell et al., 1999). From this perspective, the strategies employed by star-nosed moles to limit or prevent body cooling at low temperatures are of particular interest. One potential mechanism that could augment or substitute for primary metabolic heat production at low air temperatures is the heat increment of feeding or HIF (MacArthur and Campbell, 1994; Chappell et al., 1997; Hawkins et al., 1997). The ‘apparent’ HIF, defined as the unavoidable liberation of heat that ensues from feeding, can be partitioned into two components. The first is associated with the mechanical costs of feeding (hereafter termed ‘mechanical HIF’) and includes 301 The Journal of Experimental Biology 203, 301–310 (2000) Printed in Great Britain © The Company of Biologists Limited 2000 JEB2356