Social behavior and space-use of young of ground-dwelling squirrel species with different levels of sociality [Comportement social et utilisation de l'espace des jeunes écureuils terrestres avec différents niveaux de socialité].

Résumé

Comparisons among young of ground-dwelling squirrels species with diffrent adult sociality indicate patterns of interaction during development that may influence the evolution of complex sociality. Social behavior nd spatial overlap of weaned young with their mothers, littermates, non-littermate young, and adult conspecifics were compared among Gunnison's prairie dog (Cynomys gunnisoni), Yellow-bellied marmots (Marmota flaviventris), Columbian ground squirrels (Spermophilus columbianus), and thirteen-lined ground squirrels (S. tridecemlineatus). The adult social organiszation 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 youg 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 occured 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 mittermates, and occured 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 o littermates. Thus, in the more social ground-dwelling squirrels species, cohesive behaviors between mother and offspring oassociated with prolonged spatil overlap probably is the mechanism that establish es social groups and represents post-weaning parental reproductive investment in nonreproductive offspring. However, the tokerance and amicability of adults toward young other than their own offspring is likely a crucial step in the evolution of complex sociality.