The effect of woodland restoration on bats in a metropolitan environment
Debra A. Scott, MS
Advisor: Stanley D. Gehrt
Urban expansion fragments natural habitats, which can increase wildlife susceptibility to invasive species, predation, disease, and pollution. However, these habitat fragments may be useful for some wildlife species. Recently, many organizations have made efforts to preserve and restore (e.g., prescribed burning, invasive/exotic species removal, snag recruitment, draintile disablement, and deer management) natural areas in metropolitan areas, which led to changes in forest structure, such as reduced tree and shrub densities and decreased canopy cover. This alteration may affect how species, such as bats, use forest fragments in urban environments.
Bats are highly vagile and are able to exploit habitat patches, particularly woodlands, in urban matrices. In North America, bats use forests for foraging, roosting, and/or rearing young. In this study, I determined relationships between (1) restoration efforts and general bat activity, (2) general bat activity and microhabitat characteristics (3) interspecific variation with woodland variables, and (4) roost selection of Myotis septentrionalis and Lasiurus borealis in woodland fragments.
In the summers of 2004 and 2005, I used ultrasonic detectors to monitor both general and species-specific bat activity in 9 forest preserves that are in various stages of restoration. I identified 5,074 of 7,652 collected bat passes to species during 5,760 detector hours. Prescribed burning and invasive species removal were positively related to general bat activity. General bat activity was positively related to small tree density (7.7-20 cm DBH) and inversely related to shrub density and clutter at 0-6 m heights.
I used partial canonical correspondence analysis to determine relationships between vegetation variables and inter-specific variation. L. borealis were associated with small and medium tree densities and inversely related to clutter at 0-9 m. Myotis spp. were positively associated with canopy cover, clutter at 6-9 m, and small and medium tree densities. Lasionycteris noctivagans activity was associated with more open forests. Eptesicus fuscus was not strongly associated with any measured vegetation variable. In 2005, I radio-tracked 5 M. septentrionalis and 6 L. borealis to determine roost, plot, and stand characteristics that may clarify roost selection in urban environments. M. septentrionalis roosts were positively associated with snags that had exfoliating bark and were located in unrestored woodlands. L. borealis roosts were primarily located in unrestored woodlands and in residential lawns. Bats tended to forage in areas that had received restoration and reduced understory clutter, but they may roost in unrestored portions of the woodlot.