The genera Meles and Martes both belong to the family Mustelidae, both exhibit similar life history traits, ecology and foraging behaviour, and yet while Meles species are facultatively social, all Martes species are solitary. We compare and contrast the socio-biology of these two genera, establishing that as generalist omnivores both experience similar conditions of resource dispersion, but have intrinsic differences in their morphological and physiological capacity to exploit resources. The rotund body-type of badgers predisposes them to be able to tolerate conditions of restricted food security, by buffering periods of scarcity with increased body-mass. Badgers also use torpor to cope with seasonal food scarcity, and conserve energy by remaining within complex subterranean dens. Martens, in contrast, must maintain a lean, elongate body-type for effective hunting and thus do not store energy as increased body-mass to a comparable extent. Martens do not exhibit torpor and their dens are simple. We conclude that these differences prevent martens from being able to tolerate restricted food security; the type of precursive aggregation fundamental to the formation of social groups observed in badgers. We argue that the Japanese badger is transitionary in the development of integrated social organisation, forming spatial groups with extended juvenile philopatry.