Social thermoregulation in least shrews, Cryptotis parva

Abstract

Abstract:Cryptotis parva exhibits a geographic range and ecological requirements unique among North American soricines: it possesses a latitudinal distribution, metabolism and communal nesting pattern more like the crocidurines of the eastern hemisphere. We utilized oxygen consumption (VO 2 ) techniques to examine metabolic shifts and video to document activity patterns and dynamics of solitary and group nesting C. parva. Between ambient temperatures of 4°C and 34°C, solitary C. parva demonstrated an inverse relationship between ambient temperature (T a ) and resting metabolic rate (RMR); thermal neutral zone (TNZ) was very narrow, between a T a of 34°C and 36°C. VO 2 was measured in groups ranging in size from one to eight at T a s of 4°C, 14°C, 24°C and 34°C. The group size had a significant effect on the median RMR and median predicted Kleiber value and was more effective at reducing metabolic cost at a lower T a . In a second experiment designed to assess the effects of huddling group size and incubator T a on the T a of the nest chamber, both had significant effects. Group size had significant effects on the T a of the nest chamber at incubator temperatures of 5°C, 10°C, 15°C and 32°C, but not at 25°C. We found no behavioral or physiologic evidence of heterothermy.

Metabolic Scaling in Complex Living Systems

“…Thus, for a wide range of huddle sizes, SA theory predicts that total group metabolic rate should show nonlinear (concave upward) scaling with total group mass. Recent studies on the least shrew and Natal mole-rat support this prediction [317,318]. As expected, small huddles exhibit negatively allometric scaling, whereas large huddles display near isometric (or perhaps even positively allometric) scaling ( Figure 2).…”

“…As predicted, small huddles often show near 2/3-power scaling, whereas large huddles that expand largely in two dimensions (by adding individuals horizontally rather than vertically) show steeper scaling [200][201][202][203]. Or equivalently for mass-specific metabolic rate, small huddles show near −1/3-power scaling (mean b ± 95% confidence intervals = −0.347 ± 0.070, which is not significantly different from −1/3, based on data for 13 small mammal species compiled by Canals et al [202]), whereas large huddles tend to show near 0-power scaling (see [317,318]). Thus, for a wide range of huddle sizes, SA theory predicts that total group metabolic rate should show nonlinear (concave upward) scaling with total group mass.…”

“…Scaling of group resting metabolic rate (R) with total group mass (M) in the least shrew (Cryptotis parva) and Natal mole rat (Cryptomys hottentotus natalensis) at 14 °C (data from[317,318] and M. Scantelbury, personal communication). The number by each point refers to group size.…”

Cognitive skills of common shrews (Sorex araneus) vary with seasonal changes in skull size and brain mass

“…During winter, vertebrates use two main strategies: migration or hibernation. These are usually combined with morphological adaptations such as improving insulating tissues, or changes in behavior including food storing or communal thermoregulation (Merritt and Zegers, 2014). This can be associated with seasonal changes in certain cognitive capacities and the brain structures responsible for those skills (Sherry, 2006).…”

The role of competition in driving species global distributions: Soricid shrews as a case study

“…A high BMR allows shrews to generate body heat; as such, a lower BMR implies that those species whose distributions reach colder regions have to rely on other mechanisms to maintain body heat. For instance, Cryptotis parva , deals with cold by nest huddling (Merritt & Zegers, ), a behavioural trait that is characteristic of the subfamily Crocidurinae. On the other hand, species of the genus Cryptotis have adapted to a semifossorial lifestyle as a strategy to cope with warm climates (He et al., ; Woodman & Gaffney, ).…”