We probably all know someone who lives a solitary life. But not everyone realises that there are solitary individuals in the animal kingdom, too. Examples of solitary species are some shrews, and large predators, such as black bears (Ursus americanus) and leopards (Panthera pardus).
Solitary living is defined by the social organisation of individuals, where both males and females sleep and forage alone for more than 50% of the time and mainly meet for courtship and mating.
My PhD advisor, Carsten Schradin, and I have examined solitary living among mammals based on evidence from palaeontology as well as from comparative studies. Our findings suggest that these mammals’ ancestors lived in pairs, not alone – which suggests that solitary living must have evolved as a specific adaptation.
