Gromov V.G. 2017. The evolution of sociality in rodents: a family affair // Russian J. Theriol. Vol.16. No.1: 47–65 [in English].
Vladimir S. Gromov [email@example.com], A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninsky pr. 33, Moscow 119071, Russia.
ABSTRACT. Sociality means group-living. Among rodents, the most social species live in family groups that consist as a rule of not numerous individuals. Hence, the evolution of sociality among rodents is not a group-size evolution. A family-group lifestyle is associated with long-lasting pair bonds, participation of both parents in care of young, and cooperation in different activities. In family groups, cooperation starts from the very beginning when a breeding pair establishes, protects and marks its home range, digs burrows or constructs other shelters, and provides care-giving activities. Direct parental care (especially paternal care) by means of tactile stimulation of the young is suggested to promote long-lasting pair bonds and development of subsequent parental behaviors in sub-adult and adult males that is so typical of highly social rodent species. This phenomenon has an epigenetic nature and could be considered as ‘stimulation of similar with the similar’. Cooperation extends and intensifies when the size of family groups increases as a result of delayed dispersal of the offspring. According to the proposed conceptual model, family groups could be formed under any ecological conditions, irrespective of predation pressure or resource distribution, given that mating pairs and, furthermore, family groups are more competitive due to cooperation than solitary conspecifics. The main driving forces are proximate mechanisms related to tactile stimulation of young individuals during their early postnatal development and cooperation. This conceptual model provides a better understanding of the evolution of sociality (i.e. transition to a family-group lifestyle) in different rodent taxa.
KEY WORDS: rodents, sociality, evolution, family-group lifestyle, parental behavior, cooperation, tactile stimulation, epigenetic theory.