Author: Debra A. ScottPublisher:
ISBN:
Category : Bats
Languages : en
Pages : 196
Book Description
Abstract: Urban expansion fragments natural habitats, which can increase susceptibility of wildlife to invasive species, predation, disease, and pollution. However, these habitat fragments may benefit some wildlife species. Recently, many organizations have made efforts to maintain and restore (e.g. through prescribed burning, invasive/exotic species removal, snag recruitment, drain tile disablement, and deer population control) natural areas in metropolitan areas, which led to changes in forest structure, such as reduced tree and shrub densities and decreased canopy cover. Habitat restoration may affect how species, such as bats, use forest fragments in urban environments. Bats are highly vague and are able to exploit habitat patches, particularly woodlands, in urban landscapes. In North America, bats use forests for foraging, roosting, and/or rearing young. Previous studies have shown a positive relationship between bat activity and woodlands in urban environments, and have suggested the importance of microhabitat to bat activity. I determined relationships between (1) restoration efforts and general bat activity, (2) general bat activity and microhabitat charactersitics (3) interspecific variation with woodland variables, and (4) roost selection of northern myotis (Myotis septentrionalis) and red bats (Lasiurus borealis) in woodland fragments. During 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. Restoration variables and general bat activity were compared using linear regression and Akaike's Information Criterion (AIC) for model selection. Prescribed burning and invasive species removal were positively related to general bat activity. Relationships between general bat activity and vegetation variables were determined using mixed-effects linear regression models. Model fit was compared using AIC. 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 with site and year as covariables to determine relationships between vegetation variables and bat species. Red bats 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. Silver-haired bat (Lasionycteris noctivagans) activity was associated with more open forests. Big brown bats (Eptesicusfuscus) were not strongly associated with any measured vegetation variable. In 2005, I radio-tracked 5 northern myotis and 6 red bats to determine roost, plot, and stand characteristics that may clarify roost selection in urban environments. Northern myotis' roosts were positively associated with snags that had exfoliating bark and were located in unrestored woodlands. Red bat roosts were primarily located in unrestored woodlands and in residential lawns. These results suggest bats may respond to some forms of woodland restoration in urban landscapes. Sites that had repeated measures of restoration had greater overall bat acitivity. However, species-specific responses to vegetation and to roost selection differed and should be taken into consideration when developing management plans.