Bite force in the strictly subterranean rodent family of African mole-rats (Bathyergidae) : the role of digging mode, social organization and ecology

Abstract

Bite force is an ecologically relevant performance trait that has been measured to better understand the adaptations to diet and habitat use. Moreover, bite force is relevant in understanding reproductive success, as well as inter- and intraspecific competition. African mole-rats (Bathyergidae, Rodentia) are a unique clade of mammals that use different digging strategies, show different types of social organization and occur in ecologically diverse savanna habitats in sub-Saharan Africa. Whereas previous studies have suggested these animals have exceptionally high bite forces, the ecological and other proximate and ultimate drivers of variation in bite force in the group remain unstudied. In the present study we measured in vivo bite force of 394 adult specimens from 10 African mole-rat species including all genera within the family. Our results show that in African mole-rats digging mode is a major driver of variation in bite force, with chisel-tooth diggers being stronger biters than scratch diggers. Moreover, species living in habitats characterized by low and irregular precipitation patterns and in soils with a high content of coarse particles have a higher bite force than species occupying habitats with a regular rainfall pattern and fine soil types. This suggests that bite force in bathyergids has evolved in concert with rainfall and soil characteristics of different savanna habitats, which have contributed to the successful radiation of these subterranean mammals across sub-Saharan Africa.