Silvis, A., A.B. Kniowski, S.D. Ghert, and W.M. Ford. 2014. Roosting and foraging social structure of the endangered Indiana bat (Myotis sodalis) . PLos ONE 9(5):1-12 (e9637)
Social dynamics are an important but poorly understood aspect of bat ecology. Herein we use a combination of graph theoretic and spatial approaches to describe the roost and social network characteristics and foraging associations of an Indiana bat (Myotis sodalis) maternity colony in an agricultural landscape in Ohio, USA. We tracked 46 bats to 50 roosts (423 total relocation events) and collected 2,306 foraging locations for 40 bats during the summers of 2009 and 2010. We found the colony roosting network was highly centralized in both years and that roost and social networks differed significantly from random networks. Roost and social network structure also differed substantially between years. Social network structure appeared to be unrelated to segregation of roosts between age classes. For bats whose individual foraging ranges were calculated, most shared foraging space with at least one other bat. In total, 47% and 43% of Indiana bat dyads in 2009 and 2010 respectively showed more than expected overlap of foraging areas. Colony roosting area differed between years, reflecting an increase in roost network centralization, but the roosting area centroid shifted only 332 m. In contrast, whole colony foraging area use was similar between years. Random roost removal simulations suggest that Indiana bat colonies may be robust to loss of a limited number of roosts, but may respond differently from year to year. Our study emphasizes the utility of graphic theoretic and spatial approaches for examining the sociality and roosting behavior of bats. Detailed knowledge about the relationships between social and spatial aspects of bat ecology could greatly increase conservation effectiveness by allowing more structured approaches to roost and habitat retention, and possibly creation, for the Indiana bat as well as other tree-roosting, socially-aggregating bat species.