硬木森林中蝙蝠活动的比较

A Comparison of Bat Activity in a Managed Central Hardwood Forest KATHERINE L. CALDWELL AND TIMOTHY C. CARTER Department of Biology, Ball State University Muncie, Indiana 47306 AND JASON C. DOLL Department of Biology, Ball State University, Muncie, Indiana 47306 Department of Biological and Physical Sciences, University of Mount Olive, 634 Henderson Street, Mount Olive, North Carolina 28365 ABSTRACT.—Bats exploit forest resources based on species-specific adaptations, resulting in differences in activity across forested landscapes. Forest management practices alter forests, impacting species differently and presumably affecting bat activity. Application of forest management that promotes species-specific bat conservation requires further understanding of bat response to silvicultural practices. We surveyed timber harvest treatments on two Indiana State Forests to compare bat activity across forest management treatments, in forests adjacent to harvests, and at locations across the harvest-forest gradient from May to July in 2013 and 2014. We used Wildlife Acoustics Song Meter SM2BATþ detectors and Kaleidoscope Pro analysis software to survey bats in relation to four treatment types: clear cut, patch cut, shelterwood preparatory cut, and intact forest. Detectors were deployed at two points within each treatment and three points on the forested periphery of treatments and recorded for three consecutive nights. We examined bat activity using N-mixture models that estimate abundance and probability of detection for an open population and used Akaike’s Information Criterion to select the best models. Based on identification of acoustic calls, eastern red bats and hoary bats were more active in harvest treatments than control treatments. Big brown, eastern red, and tri-colored bats were most active at harvest edges. Northern long-eared and Indiana/little brown bats were most active at harvest edges and in adjacent forest and hoary bats were most active at harvest centers. Differences in bat activity across these managed forests suggest bat assemblages benefit from management that employs an array of silvicultural methods, provides edge habitat, and maintains adjacent forest stands. Our results can be used to predict effects of forest management practices on species-specific bat activity to maximize bat usage of forests. INTRODUCTION Approximately 75% of forest cover has been lost in the state of Indiana over the last two centuries due to agricultural expansion, logging practices, urban development, and human population growth (Carman, 2013). Indiana’s forests are recovering as better management practices are implemented and farmland reverts to forest, yet forests are scarce and fragmented on much of the landscape. Additionally, increased land development and slowing in farmland reversion suggests Indiana’s forested land may be nearing a peak (Gormanson et al., 2016). Silvicultural practices that alter remaining forests must be well understood in regard to their ecosystem impacts to ensure the continual conservation of forest-dependent bats (Grindal, 1996; Hayes and Adam, 1996; Menzel et al., 2002). This is especially true in light of the recent drastic population declines associated with White-nose Syndrome (Blehert et al., 2009; and see USFWS, 2018). 225 Downloaded From: https://bioone.org/journals/The-American-Midland-Naturalist on 19 Dec 2019 Terms of Use: https://bioone.org/terms-of-use Access provided by University of LeicesterForest ecosystems serve as the primary habitat for many temperate bat species by providing essential foraging and roosting habitat (Barclay and Brigham, 1991; Barclay and Kurta, 2007). Bats are thought to select forested habitats based on four key characteristics: density of forest structure, roost availability, prey abundance, and water availability (Hayes and Loeb, 2007). All of these characteristics can be affected by forest management practices (Krusic et al., 1996; Fenton, 2001; Menzel et al., 2005). In particular timber harvests can directly alter forest structure and number of available roosts (Jones et al., 2000; Loeb and Waldrop, 2008; Adams et al., 2009). Bats vary in terms of morphology and echolocation call characteristics and these traits affect how bats forage in different habitats (Aldridge and Rautenbach, 1987; Norberg and Rayner, 1987; Humes et al., 1999; Menzel et al., 2002; Patriquin and Barclay, 2003). Largerbodied bats have high wing loadings and high aspect ratios resulting in faster flight with less maneuverability. These bats use lower frequency calls than smaller-bodied bats and calls of large bats attenuate at slower rates (Aldridge and Rautenbach, 1987). These morphological and echolocation characteristics promote in-flight prey capture and allow larger-bodied bats to forage efficiently in open areas (Aldridge and Rautenbach, 1987; Jones et al., 2000; Menzel et al., 2005). In contrast, smaller-bodied bats have lower wing loadings, wing aspect ratios, and higher frequency echolocation calls; therefore, these bats are slower and more maneuverable in flight but also have a shorter call range when compared to larger bats (Aldridge and Rautenbach, 1987; Norberg and Rayner, 1987). Smaller-bodied bats typically are categorized as clutter-adapted due to their ability to forage within forest clutter where they may glean prey from vegetation surfaces in addition to capturing prey in flight (Norberg and Rayner, 1987). Previous work has shown that bats are generally more active in timber harvest areas than in unharvested forests (Grindal and Brigham, 1998; Humes et al., 1999; Menzel et al., 2005; Titchenell et al., 2011); however, effects vary by species due to differences in morphology and echolocation call structure. In particular, big brown bats (Eptesicus fuscus), eastern red bats (Lasiurus borealis), hoary bats (Lasiurus cinereus), and tri-colored bats (Perimyotis subflavus) show higher activity in cut areas in the coastal plain of the Carolinas (Menzel et al., 2002; Morris et al., 2010). Titchenell et al. (2011) found higher overall bat in shelterwood harvests, and Menzel et al. (2002) found more bat activity in group selection harvests compared to unharvested forest. Additionally, Patriquin and Barclay (2003) found an increase in total bat activity in clear cuts compared to unharvested forest in Alberta, Canada, but northern long-eared bats (Myotis septentrionalis), a clutter-adapted species, were less active in clear cuts. Clearly a more detailed understanding of timber harvest influence on bat species is needed to apply forest management strategies that promote bat conservation. Forest management practices such as timber harvests can create hard edges at the harvestforest interface. Bats use these edges for navigation, commuting, and foraging (Clark et al., 1993; Walsh and Harris, 1996; Grindal and Brigham, 1999; Hogberg et al., 2002). Forest edges may also offer greater insect availability (Grindal and Brigham, 1999; Morris et al., 2010), because these boundaries potentially act as windbreaks that concentrate large amounts of insects (Pasek, 1988; Swystun et al., 2001). Higher bat activity along harvest edges, rather than in harvest centers or forest interiors, has been widely documented (Menzel et al., 2002; Patriquin and Barclay, 2003). Krusic et al. (1996) found overall higher concentrations of bat activity at forest edges than at locations within forest interiors in a study in New Hampshire and Maine, but calls were not classified to species. A study in Alberta, Canada showed greater activity of northern long-eared and little brown bats (Myotis lucifugus) at harvest edges over harvest center (Hogberg et al., 2002). Alternately, Morris et al. THE AMERICAN MIDLAND NATURALIST 226 181(2) Downloaded From: https://bioone.org/journals/The-American-Midland-Naturalist on 19 Dec 2019 Terms of Use: https://bioone.org/terms-of-use Access provided by University of Leicester(2010) found northern long-eared and southeastern bats (Myotis austroriparius) foraging in stand interiors and avoiding edges in North Carolina. Though studies have documented increased bat use of harvest edges, results differ among studies and the extent of edge influence on bat activity in adjacent forest is not well understood. Jantzen and Fenton (2013) examined bat activity along a continuum across the agriculture-forest interface in Ontario, Canada, and found hoary bats, big brown/silver-haired bats (Lasionycteris noctivagans), northern long-eared bats, and little brown bats to show maximum activity along the edge. However, similar studies in a managed forest landscape are lacking (but see Menzel et al., 2002; Morris et al., 2010). Acoustic technology has been widely used in bat forest management studies and can yield stronger comparisons between treatments using statistical analyses that account for imperfect detection probability (P , 1) (Duchamp et al., 2006). Recent studies have used occupancy modeling to compare bat use of differing habitat types taking into account imperfect detection (Yates and Muzika, 2006; Hein et al., 2009; Bender et al., 2015); however, meeting the population closure assumption of occupancy analyses is challenging given bats are able to fly great distances in a short time frame. Estimating bat call abundance using Nmixture models for open populations that account for imperfect detection may be more suitable for studies that cannot ensure population closure between sites (Dail and Madsen, 2011). To examine the effect of timber harvest on bat activity at multiple scales, we conducted this study on Morgan-Monroe and Yellowwood State Forests, Indiana. Our study focused on several silvicultural treatments designed to regenerate oak (Quercus spp.) and hickory (Carya spp.) within the larger intact forests. Our objectives were: (1) to compare bat activity relative to forest treatment areas for common species on our study site and (2) to compare bat activity across the harvest-forest gradient. We hypothesized: (1) larger-bodied bats (big brown bat, hoary bat, and eastern red bat) would be more active in harvest treatments than in control treatments based on previous studies and smaller-bodied bats [northern longeared bat, Indiana bat (Myotis sodalis), little brown bat, and tri-colored bat] would be more active in control treatments than in harvest treatments; and (2) larger-bodied bats would be more active at the harvest edge based on previous research (Menzel et al., 2002; Morris et al., 2010) and smaller-bodied bats would be more active in interior forest due to their clutter tolerance.