The gut morphology of the African ice rat, Otomys sloggetti robertsi, shows adaptations to cold environments and sex-specific seasonal variation.

We studied the gut morphology of the ice rat Otomys sloggetti robertsi, a non-hibernating murid rodent endemic to the sub-alpine and alpine regions of the southern African Drakensberg and Maluti mountains. The gut structure of O. s. robertsi is well adapted for a high fibre, herbivorous diet, as is the case with other members of its subfamily Otomyinae. Despite the broad similarity in gross gut morphology with mesic- and arid-occurring otomyines, O. s. robertsi has a larger small intestine, caecum, stomach volume and parts of the colon, which we suggest are adaptations for increased energy uptake and/or poor diet quality in alpine environments. However, O. s. robertsi has a smaller larger intestine than other otomyines, perhaps because it occupies a mesic habitat. Seasonal sexual differences occurred, with females increasing dimensions of the stomach, small intestine length, caecum, and large intestine in summer. Sexual asymmetry in gut morphology may be related to increased energy requirements of females during pregnancy and lactation, indicating phenotypic plasticity in response to poor quality vegetation and a shorter growing season in alpine habitats.