Tall Timber: Roost Tree Selection of Reproductive Female Silver-Haired Bats (LASIONYCTERIS NOCTIVAGANS)

Abstract

Habitat loss is the most significant contributor to the extinction of species worldwide, and yet for many species, habitat requirements remain largely unknown. Identifying habitat is important, especially because the most cost effective strategy for conservation and management is preserving habitat before it is converted or degraded rather than trying to restore it after the fact. Identifying habitat is also important from a scientific perspective because it can help to explain some of the ecological choices made by individuals when potentially conflicting priorities exist. Habitat requirements change for many species, both seasonally and throughout their life cycles, and identifying habitat during key developmental or life history periods will provide further information about priorities of these species. North American bat species show distinct differences in the habitat they use during the summer and winter, which provides us with an opportunity to understand how the selection pressures of reproduction have shaped the habitat use of these species. Silver-haired bats (Lasionycteris noctivagans) are small Vespertilionids that are solitary during their regional seasonal migration, but form small groups or maternity colonies of reproductive females on the summering ground. I captured female silver-haired bats during the reproductive season in Cypress Hills Interprovincial Park, Saskatchewan, Canada and characterized the trees that they roosted in during the day to understand why they chose the roosts that they did. These bats chose trees that were near other dead trees with cavities, presumably to reduce the cost of roost switching, a behaviour commonly undertaken by tree-roosting Vespertilionids. Bats also chose trees that were in plots with higher basal area. Roost choices did not vary over the course of the reproductive season, likely because the priorities of pregnant and lactating bats were similar. I quantified the roost characteristics chosen by silver haired bats while pregnant and lactating. The analysis suggests that the surrounding trees can also be important factors in roosting decisions. Protecting habitat critical for reproduction can be an important conservation step, but understanding why it is critical can yield even more clues for managing both natural resources and bats species.