Comparative Biochemistry and Physiology Part A 123 (1999) 293 – 298 Fasting metabolism and thermoregulatory competence of the star-nosed mole, Condylura cristata (Talpidae: Condylurinae) Kevin L. Campbell *, Ian W. McIntyre, Robert A. MacArthur Department of Zoology, Uniersity of Manitoba, R3T 2N2, Winnipeg, Canada Received 27 December 1998; received in revised form 10 March 1999; accepted 7 April 1999 Abstract Metabolic and body temperature (T b ) responses of star-nosed moles (Condylura cristata ) exposed to air temperatures ranging from 0 to 33°C were investigated. The thermoneutral zone of this semi-aquatic mole extended from 24.5 to 33°C, over which its basal rate of metabolism averaged 2.25 ml O 2 g -1 h -1 (45.16 J g -1 h -1 ). This rate of metabolism is higher than predicted for terrestrial forms, and substantially higher than for other moles examined to date. Minimum thermal conductance was nearly identical to that predicted for similar-sized eutherians and may represent a compromise between the need to dissipate heat while digging and foraging in subterranean burrows, and the need to conserve heat and avoid hypothermia during exposure to cold. C. cristata precisely regulated T b (mean SE =37.7 0.05°C) over the entire range of test temperatures. Over three separate 24-h periods, T b of a radio-implanted mole varied from 36.6 to 38.8°C, and generally tracked level of activity. No obvious circadian variation in T b and activity was apparent, although cyclic 2 – 4 h intervals of activity punctuated by periods of inactivity lasting 3 – 5 h were routinely observed. We suggest that the elevated basal metabolic rate and relatively high T b of star-nosed moles may reflect the semi-aquatic habits of this unique talpid. © 1999 Elsevier Science Inc. All rights reserved. Keywords: Condylura; Star-nosed mole; Metabolism; Thermal biology; Body temperature; Conductance; Insectivore; Activity pattern www.elsevier.com/locate/cbpa 1. Introduction The star-nosed mole (Condylura cristata ), distin- guished by its strange and conspicuous [22] fleshy-ap- pendage proboscis, is the only member of the subfamily Condylurinae [29]. Unique among North American moles for its semi-aquatic habit and predilection for moist soils bordering on streams and lakes, the star- nosed mole is an adept burrower and excellent swimmer [13,14]. Direct observations of star-nosed moles indicate an active lifestyle, prompting speculation of a voracious appetite and ‘high metabolism’ [4,5,13,31,33]. Yet few data exist on even the most basic energetics of this curious invertebrativore. Indeed, information of this nature is limited to metabolic measurements obtained from two immature moles held at 27–28°C [37] and from a single, restless 60-g specimen [28] that pre- sumably was held at a similar air temperature. The star-nosed mole ranges considerably farther north than any other North American talpid [29]. In fact, these animals have been observed tunneling through snow and even diving under ice during winter [13,26,33]. Moreover, analysis of stomach contents indi- cate that aquatic invertebrates are taken year round [13,30], and reportedly occur in the diet most frequently during winter. These observations imply a high level of thermoregulatory competence in this species, perhaps coupled with an elevated basal metabolic rate (BMR). Non-hibernating small mammals inhabiting cold envi- ronments, including semi-aquatic forms, often exhibit higher BMRs and lower heat transfer coefficients than predicted from allometry [9,18,34]. Though controver- sial, it has been speculated that these features are consistent with the high rates of thermogenesis and risks of hypothermia posed by chronic exposure to cold [8,32]. Like aquatic foraging, burrowing is considered one of the most energetically demanding activities engaged * Corresponding author. Present address: Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancou- ver, British Columbia, Canada; tel.: +1-604-822-6759; fax: +1-604- 822-2416. E-mail address: campbelk@zoology.ubc.ca (K.L. Campbell) 1095-6433/99/$ - see front matter © 1999 Elsevier Science Inc. All rights reserved. PII:S1095-6433(99)00065-3