Body temperature patterns in two syntopic elephant shrew species during winter

Abstract

We measured body temperature (T b) in free-ranging individuals of two species of elephant shrews, namely western rock elephant shrews ( Elephantulus rupestris) and Cape rock elephant shrews ( E. edwardii), during winter in a winter-rainfall region of western South Africa. These syntopic species have similar ecologies and morphologies and thus potential for large overlaps in diet and habitat use. Unexpectedly, they displayed different T b patterns. Western rock elephant shrews were heterothermic, with all individuals decreasing T b below 30 °C on at least 34% of nights. The level of heterothermy expressed was similar to other species traditionally defined as daily heterotherms and was inversely related to T a, as is commonly seen in small heterothermic endotherms. In contrast, Cape rock elephant shrews rarely allowed their T b to decrease below 30 °C. The level of heterothermy was similar to species traditionally defined as homeotherms and there was no relationship between the level of heterothermy expressed and T a. In both species, the minimum daily T b was recorded almost exclusively at night, often shortly before sunrise, although in some individuals minimum T b occasionally occurred during the day. The interspecific variation in T b patterns among Elephantulus species recorded to date reiterates the importance of ecological determinants of heterothermy that interact with factors such as body mass and phylogeny.