Roosting behavior and habitat dynamics of male Indiana bats (Myotis sodalis) following a large-scale natural disturbance

Abstract

Indiana bats (Myotis sodalis) have been the subject of numerous ecological studies, partly because they are endangered. A majority of research has focused on maternity colonies and relatively less is known about males. Previous research identified habitat and described fidelity of a population of male Indiana bats at South Goldson Cave, Pulaski Co., Kentucky. Mortality of pine trees (Pinus) following a large infestation of southern pine beetles (Dendroctonus frontalis) at the site provided an opportunity to gain insight into ecological requirements of male Indiana bats, and determine if availability of dead trees influences fidelity. This dissertation 1) provides a summary of the conservation and life history of Indiana bats, 2) identifies microhabitat characteristics of male Indiana bats using natural roosts, and northern long-eared bats (Myotis septentrionalis) using bat boxes, 3) identifies macrohabitat variables that influenced selection by Indiana bats, 4) determines if fidelity changed following the infestation of southern pine beetles, and 5) estimates how long roosts may remain suitable for use by bats. Most roosts were under exfoliating bark of dead pine trees, ca. 9 m from the ground, with sunny or partially shaded conditions. Bat boxes were used infrequently by northern long-eared bats (7 of 46 boxes), primarily during summer. Inadequate temperature regimes may have limited use of bat boxes to summer. Habitats selected by Indiana bats occurred in stands 1) dominated by pines with few ‘other’ trees present, and 2) with greater mean diameters at breast height, basal area, abundant dead hardwoods, and less abundant living hardwoods. Use of core areas over time was influenced by local availability of dead trees. Bats used pine trees as they became available following the infestation of southern pine beetles. Fidelity increased slightly during 2001-2003, but was statistically similar to data reported prior to the infestation. Roosts decayed over time; most pines were predicted to become unsuitable 2-7 years from the date they were used by bats, whereas hardwoods were predicted to remain suitable indefinitely. Used habitats likely provided warm temperatures that aided in thermoregulation. Abundant dead hardwood trees in habitats that were used by Indiana bats suggests that 1) bats use areas with many potential alternate roosts, and 2) hardwoods may have been used frequently before natural disturbances killed large numbers of pines. Although male Indiana bats used ephemeral roosts created by natural disturbance, bats showed fidelity to core areas as well as individual trees. Importance of natural disturbances to bats may depend on time intervals between disturbances.