Variation of social strategies within and between individual black-tailed prairie dogs (Cynomys ludovicianus) during the reproductive season

Abstract

Sociality describes the tendency for members of a species to associate in a group based on social attraction. To balance the trade-offs of sociality, the fitness consequences (and therefore proclivity towards being social) should be expected to vary across individuals and within the same individual, across time. We used social network analysis to evaluate the causes and consequences of within- and between-individual variation in sociality in a wild population of black-tailed prairie dogs (Cynomys ludovicianus) during the reproductive season. We hypothesised that individuals would adjust their behaviours based on a key life-history event: reproduction. We assessed this variation by comparing differences in social behaviour between individuals in different life history stages and within individuals across the reproductive season. We predicted breeding females would increase their agonistic interactions to protect their offspring from infanticide during reproduction, while non-reproductive individuals would increase their affiliative interactions to maintain stability in their social network and increase their indirect fitness. We found that the number of social interactions decreased after reproduction for all individuals. Breeding females did not increase their agonistic interactions compared to other groups, but instead had overall decreased social interactions during reproduction, which corresponded with increased fitness. For non-breeding females, an increase of affiliative social interactions correlated with increased indirect fitness as we predicted. Our multiple-level, temporally structured analyses revealed under-realised complexities regarding within- and between-individual variation in social interactions, suggesting reproductive status dictates different social strategies to optimise fitness. Social living with conspecifics confers a range of costs and benefits, the trade-offs of which are expected to change based on life history. Therefore, individuals should modulate their sociality across life history transitions to optimise fitness. Reproductive status is known to affect socio-behavioural decisions across taxa. We used a highly social species, black-tailed prairie dogs, to investigate variation in social structure across the reproductive season, and understand both the causes and consequences of individual variation in social structure. Prairie dogs offered easily observable, dynamic social behaviours and quantifiable fitness consequences to truly demonstrate acute social change. Our results suggest that there is variation of social interactions not only within individuals over time, but also between reproductive groups in the same time period. Our analyses suggest that social variation has important consequences for fitness and should further stimulate study of temporally based analyses of social behaviour.