Capacities for and constraints of heat dissipation are considered to be important factors governing maximum intensity and duration of physical activity. Subterranean mammals are endurance diggers, but because of lack of air currents in their burrows, high relative humidity and other physical constraints, the capacity of common mammalian cooling mechanisms underground is very limited. We analyzed surface and body core temperature changes after digging in soft and hard substrates in two species of African mole-rats (Bathyergidae, Rodentia); the social giant mole-rat Fukomys mechowii and the solitary silvery mole-rat Heliophobius argenteocinereus. As expected, we observed an increase of body core temperature in both species after digging in both substrates. Surprisingly, and contrary to our expectations, we observed remarkable decrease of mole-rats' surface temperature immediately after the end of the digging trials. This decrease was greater in soft and moister soil than that in hard and drier soil. Our results suggest that mole-rats may effectively avoid overheating in burrows by effective cooling while digging, especially in wet soil. This indicates that burrowing in soils moistened by rains could be easier than previously thought contributing thus to mole-rats success in challenging environment of subterranean burrows.

Department of Animal Physiology Faculty of Science University of South Bohemia in České Budějovice České Budějovice 370 05 Czech Republic

Department of General Zoology Faculty of Biology University of Duisburg Essen Essen 45117 Germany

Department of Technology and Animal Breeding Technique Institute of Animal Science Uhříněves Prague 104 00 Czech Republic

Department of Zoology Faculty of Science University of South Bohemia in České Budějovice České Budějovice 370 05 Czech Republic

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