CLIMATIC ADAPTATION OF BODY-SIZE AMONG POUCHED MICE (SACCOSTOMUS-CAMPESTRIS, CRICETIDAE) IN THE SOUTHERN AFRICAN SUBREGION

Morphological variation was studied among 209 pouched mice (Saccostomu s campestris, Peters, 1846) from 104 localities in the southem African subregion. Climatic variables for these localities were generated usi ng a climatic surface model developed with data from existing meteorol ogical stations. These estimates of temperature, rainfall and seasonal variability were strongly correlated with latitude, so that the diffe rent climatic factors covaried. Extemal measurements (body, tail and e ar length) and body mass were strongly correlated with condylo-basal s kull length which was taken as a more reliable measure of body size. G eographical variation in body size was significantly correlated with l atitude, temperature and seasonality although these correlations appea red to be largely the result of a positive relationship between size a nd rainfall. In contrast, temperature apparently had little effect on morphology as there were no clear correlations between temperature and the size of appendages (tail or ear length). Rainfall might be more i mportant than ambient temperature as a factor influencing body size in small fossorial and semi-fossorial mammals which spend most of their lives in warm subteffanean microhabitats. Meanwhile, the smaller body size of pouched mice from localities with lower rainfall may represent an adaptation to reduce total energy requirements in arid and semi-ar id areas where primary production and food availability is low.