Social behavior and space-use of young of ground-dwelling squirrel species with different levels of sociality

Publisher Website
Google Scholar
Abstract
Comparisons among young of ground-dwelling squirrel species with different adult sociality indicate patterns of interaction during development that may influence the evolution of complex sociality. Social behavior and spatial overlap of weaned young with their mothers, littermates, non-littermate young, and adult conspecifics were compared among Gunnison's prairie dogs (Cynomys gunnisoni), yellow-bellied marmots (Marmota flaviventris), Columbian ground squirrels (Spermophilus columbianus), and thirteen-lined ground squirrels (S. tridecemlineatus). The adult social organization of these species differs markedly: Gunnison's prairie dogs are highly social, yellow-bellied marmots and Columbian ground squirrels are relatively less social, and thirteen-lined ground squirrels are asocial. In young Gunnison's prairie dogs, social cohesion and spatial overlap were high not only with the mother and littermates, but with all members of the harem. In yellow-bellied marmots, social cohesion occurred with all members of the matriline, but spatial overlap was less extensive than in prairie dogs. In Columbian ground squirrels, amicable social interactions of young were confined to the mother and littermates, and occurred less frequently than among the prairie dogs. Young of thirteen-lined ground squirrels interacted little and overlapped only briefly with their mothers; cohesive interactions were limited to littermates. Thus, in the more social ground-dwelling squirrel species, cohesive behaviors between mother and offspring associated with prolonged spatial overlap probably is the mechanism that establishes social groups and represents postweaning parental reproductive investment in non-reproductive offspring. However, the tolerance and amicability of adults toward young other than their own offspring is likely a crucial step in the evolution of complex sociality.