Academic journal article The American Midland Naturalist

Multi-Scale Roost Site Selection by Rafinesque's Big-Eared Bat (Corynorhinus Rafinesquii) and Southeastern Myotis (Myotis Austroriparius) in Mississippi

Academic journal article The American Midland Naturalist

Multi-Scale Roost Site Selection by Rafinesque's Big-Eared Bat (Corynorhinus Rafinesquii) and Southeastern Myotis (Myotis Austroriparius) in Mississippi

Article excerpt

ABSTRACT.-Rafinesque's big-eared bats (Corynorhinus rafinesquii; RBEB) and southeastern myotis (Myotis austroriparius; SEM) are species of concern whose current population statuses are unknown. Bottomland hardwood forests are important roosting habitat for RBEB and SEM; however, ≥80% of these forests have been cleared or degraded in Mississippi. Limited information on roost site requirements exists across either species ranges; therefore, we conducted roost surveys for RBEB and SEM in bottomland and riparian hardwood forests on Noxubee National Wildlife Refuge, Legion State Park, and Tombigbee National Forest, Mississippi, during winter 2009-2010 and spring 2010. To compare seasonal roost selection for each species we compared tree species, used 95% confidence intervals (CIs) for three tree variables [diameter at breast height (DBH), cavity volume, and opening area] and logistic regression for four landscape variables (elevation, slope, distance to nearest stream, and distance to nearest road). We used Akaike's Information Criteria corrected for small sample size and model averaging to incorporate model selection uncertainty into parameter estimates of landscape models. Based on 95% CIs, RBEB and SEM in winter used trees with greater DBH and SEM used trees with larger cavities. However, during spring, RBEB and SEM occupied trees with comparable DBH and cavity size to unoccupied trees. At the landscape scale, RBEB used roost trees at lower elevations during winter and spring. During spring, SEM used trees further from roads (Importance weight = 0.76) at lower elevations (Importance weight = 0.29) and with less slope (Importance weight = 0.25). Understanding seasonal roost site selection will improve our ability to protect habitat to ensure viable populations of these bat species.

INTRODUCTION

Rafinesque's big-eared bat (Corynorhinus rafinesquii; RBEB) and Southeastern myotis (Myotis austroriparius; SEM) are rare bats of the southeastern United States and considered species of concern throughout their range (Harvey et ai, 2006). The current population statuses are unknown (Gooding and Langford, 2004; Harvey et al., 2006). Major threats to RBEB and SEM are habitat loss and degradation caused by urbanization and timber harvest (Clark, 1990; Cochran, 1999). Bottomland hardwood forests are important to SEM and RBEB (Clark et al., 1998; Cochran, 1999), providing roosting and foraging habitat (Tiner, 1984). Only 15-25% of precolonial bottomland hardwood forests remain in the southeastern United States; therefore, availability of roost trees for bats has decreased, likely leading to decreased abundance of SEM and RBEB in the region (Mississippi Museum of Natural Science, 2005).

Roosts are critical because of the role they serve in homeostasis and social interaction (Altringham, 1996). Tree cavity roosts are often considered limiting to bats and other wildlife, because their availability varies temporally and suitable cavity trees are needed across seasons over multiple years (Kunz and Lumsden, 2003; Barclay and Kurta, 2007). Roost tree availability can be limited by land-use practices including timber harvest (Campbell et ai, 1996; Sedgeley and O'Donnell, 1999). Large tracts of bottomland hardwood forests with suitable large diameter trees are necessary to maintain populations of RBEB and SEM (Clark, 1990). Rafinesque's big-eared bat and SEM in Louisiana are usually found in bottomland hardwood forests containing baldcypress (Taxodium distichum) and water túpelo (Nyssa aquatica) (Menzel et al., 2001) with mean diameter at breast height (DBH) of 120-155 cm (Gooding and Langford, 2004). Mirowsky and Horner (1997) suggested die ratio of cavity opening size to inside cavity dimensions could be important for maintaining stable temperatures, and large cavity openings may allow bats to escape predators. Tree features, such as tree diameter (DBH 40 cm) and cavity chamber morphology, were selected for investigation due to reported influence of diese metrics in roost tree use by RBEB and SEM (Gooding and Langford, 2004; Carver and Ashley, 2008). …

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