The energy cost of voluntary running in weasels,Mustela nivalis

Abstract

SUMMARYThe small size and elongate shape of weasels (Mustela nivalis) probably evolved to facilitate movement within the burrow systems of prey species, but result in high energy costs of thermoregulation. In this study we measured metabolic rates of weasels during voluntary locomotion to determine whether energy costs of transport are also high in these unusually shaped mammals. In addition, we measured the lower and upper limits of aerobic metabolism [resting metabolic rate (RMR) and maximal oxygen consumption in forced exercise (V O2,max )], and used the wide size range of adult weasels to investigate the intraspecific scaling of energy metabolism. Finally, we combined measurements of energy use during running with radiotracking and doubly labeled water data from free-living weasels to estimate the importance of locomotor costs in daily energy budgets. We found that weasels have higher than predicted costs of running, largely because of an elevated intercept of the speed versus metabolic rate relationship. Running costs were strongly affected by the approximately fourfold range of body size in adults. As reported in other studies, the RMR of weasels was considerably higher than predicted from body mass. Maximal oxygen consumption was also higher than predicted, but factorial aerobic scope (V O2,max /RMR) was within the normal range for mammals. Intraspecific mass scaling of RMR and V O2,max did not differ from typical interspecific mammalian allometries. In wild weasels, locomotor costs comprised roughly 5% of daily energy expenditures; this low value was primarily a result of short travel times and distances.

Crouching to fit in: the energetic cost of locomotion in tunnels

“…Some researchers have observed higher than expected CoT values in mustelids, such as the least weasel (Mustela nivalis, Fig. 5; Chappell et al, 2013) and the Pacific marten (Martes caurina, Fig. 5; Flaherty et al, 2014), crediting the distinctive morphology of the mustelid form as responsible.…”

“…These ratios (∼2× RMR for tunnel locomotion; Table 3) are relatively small when compared to such rigorous activities as burrowing (which can be up to 7× RMR; Ebensperger and Bozinovic, 2000b;Luna et al, 2002) or VȮ 2,max which has been reported as 9× RMR in both weasels (Chappell et al, 2013) and mink (Williams, 1983).…”

“…Degus (gray squares; labeled Octodon) and ferrets from this study are included in the graph, but were not used in the calculation of the allometric equation; tunnel trials were averaged among individuals and indicated with a star. CoT values from mustelids (diamonds) and other <10 kg mammalian taxa (triangles) were obtained from: Chappell et al (2013), Fish and Baudinette (1999), Fish et al (2001), Flaherty et al (2010), Flaherty et al (2014), Taylor et al (1982), Williams (1983); F and M indicate female and male individuals. very different minimum threshold height tolerances (relative to standing back height) than the ferrets.…”

“…Calculating the data in this manner also permits comparison of the ferret data to other locomotor studies (e.g. Chappell et al, 2013;Flaherty et al, 2014). An alternative explanation, but not mutually exclusive to RMR, may lie with differences in the relationship between CoT and speed between large and small animals.…”

A comparison of locomotor performance of the semiarboreal Pacific marten (Martescaurina) and semiaquatic mustelids

“…For instance, long-bodied mustelids have a higher surface area to volume ratio that could result in a greater rate of heat loss than mammals of similar body mass (Brown and Lasiewski 1972;Buskirk et al 1988;Harrington et al 2003). It has been hypothesized that to compensate for this increased rate of heat loss, mustelids exhibit greater than expected basal metabolic rate (Iversen 1972;Casey and Casey 1979;Zub et al 2011;Chappell et al 2013), although experimental results are inconclusive (Harrington et al 2003). The reduced limb length, which may decrease drag while swimming (Fish 2000), coupled with the elongated body, likely leads to the higher than expected energetic costs associated with running locomotion previously recorded in mink (Williams 1983) and river otters (Lontra canadensis (Schreber, 1777)) (Williams et al 2002).…”