Basking African striped mice choose warmer locations to heat up: evidence from a field study

摘要

Basking in the sun is an important energy-saving tactic in ectotherm animals. It has also been recognized to be important in several mammal species, especially in arid environments. In particular, small mammals that have a greater surface-to-volume ratio can use basking to reduce metabolic energy expenditure by using external heat to maintain a high body temperature. If basking mainly functions to passively gain heat, animals should choose basking spots that offer a more favorable micro-climate for warming up. We tested this hypothesis in African striped mice (Rhabdomys pumilio), a diurnal species that is known to bask. Over 19 months, we displaced 138 individuals from their basking spots and immediately thereafter measured the temperature of the surface (T-s) at these spots. We expected that striped mice choose spots for basking that are warmer than random spots, especially in (1) the morning, when T-s is lower compared to afternoon, and (2) the dry season characterized by low food availability in which energy gain due to basking is more beneficial than in the moist season with high food availability. Moreover, we tested whether there are differences in relative safety (measured as available plant cover) at basking spots compared to random spots. Temperature of the surface (T-s) was significantly higher at basking spots than at random spots. However, we did not find any differences in Delta T in relation to season, time of the day or in the safety between basking and random spots. In conclusion, our study indicates that striped mice choose basking spots with a favourable microclimate characterized by higher surface temperature.