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.