Formation of social patterns in a newly assembled group of Sowell's Short Tailed Bats (Carollia sowelli)

Group-living is a typical feature of bat ecology. The present study aims at factors that drive aggregation and the formation of social patterns by studying a newly assembled group of Carollia sowelli in two observation periods, shortly after capturing the individuals, and six weeks later. Based on focal sampling, videos were recorded for three hours after dusk to capture physical contacts and social interactions of bat dyads. Using SOCPROG2.8, dyadic contact rates were analysed in terms of individual-based gregariousness, as well as of individual preferences for specific associates, and compared with the number of sociopositive interactions in bat dyads. In both observation periods, gregariousness and individual preferences for specific associates were predictors of physical contact rates. The number of socio-positive interactions, namely allogrooming, greeting and sniffing, was significantly higher in the second observation period compared to the first. Moreover, the number of socio-positive interactions, and the individual preferences for specific associates, were positively and significantly correlated in the second period, only, indicating a formation of individualised relationships. In contrast, individual gregariousness did not differ between observation periods and was negatively correlated with the number of sociopositive interactions in the second period, confirming that higher interaction rates were not a simple consequence of increased physical contact. In sum, the present study provides evidence that individualised relationships were established in a newly assembled group of C. sowelli within six weeks.