Winter roosting ecology of tricolored bats (Perimyotis subflavus) in trees and bridges

Abstract

Tricolored bats (Perimyotis subflavus) that roost in subterranean hibernacula have experienced precipitous declines from white-nose syndrome (WNS); however, understudied populations also use during winter non-subterranean roosts such as tree cavities, bridges, and foliage. Our objectives were to determine winter roost use by tricolored bats in an area devoid of subterranean roosts, determine roost microclimates to relate them to growth requirements of the fungal causal agent of WNS, and determine habitat factors influencing winter tree selection. From November to March 2017–2019, we used radiotelemetry to track 15 bats to their day roosts in the upper Coastal Plain of South Carolina and recorded microclimates in accessible tree cavities and bridges. We also characterized habitat and tree characteristics of 24 used trees and 153 random, available trees and used discrete choice models to determine selection. Roost structures included I-beam bridges, cavities in live trees, and foliage. Bridges were warmer and less humid than cavities. Roost temperatures often were amenable to fungal growth (< 19.5°C) but fluctuated widely depending on ambient temperatures. Bats used bridges on colder days (8.7°C ± 5.0 SD) and trees on warmer days (11.3°C ± 5.4). Bats selected low-decay trees closer to streams in areas with high canopy closure and cavity abundance. Bats also appeared to favor hardwood forests and avoid pine forests. Our results suggest that access to multiple roost microclimates might be important for tricolored bats during winter, and forest management practices that retain live trees near streams and foster cavity formation in hardwood forests likely will benefit this species. Our results also suggest tricolored bats using bridge and tree roosts might be less susceptible to WNS than bats using subterranean hibernaculum roosts. Thus, forests in areas without subterranean hibernacula in the southeastern United States that support bats during winter might represent important refugia from WNS for multiple species.

Changes in hibernating tricolored bat (Perimyotis subflavus) roosting behavior in response to white‐nose syndrome

“…However, warmer temperatures in southern hibernacula resulting in faster fungal growth rates could counter this effect. In the southeastern U.S., temperatures in hibernacula used by tricolored bats are often in the optimal range for P. destructans growth (i.e., 12.5–15.8°C) (Lutsch, 2019 ; Meierhofer et al, 2019 ; Newman et al, 2021 ; Sirajuddin, 2018 ) and the relatively warm hibernacula temperatures in the southeast may explain the high mortality rates observed in this region (>90%) since the arrival of WNS (Pete Pattavina, pers. comm.).…”

“…Historically, the tricolored bat was one of the most common bat species in southern hibernacula (Meierhofer et al, 2019 ; Perry & Jordan, 2020 ; Stevens et al, 2017 ). In addition to hibernating in underground structures such as caves, mines, and tunnels, they also use above‐ground structures such as bridges, culverts, storm drains, water wells, and trees (Ferrara & Leberg, 2005 ; Fujita & Kunz, 1984 ; Goering, 1954 ; Newman et al, 2021 ; Sandel et al, 2001 ; Sasse et al, 2011 ). In northern portions of their range, tricolored bats that hibernate in caves and mines usually select the warmest (7.3–11.8°C) and most humid sites within the hibernaculum (Briggler & Prather, 2003 ; Kurta & Smith, 2014 ; Raesly & Gates, 1987 ), but in Florida, where caves are warmer, they select cooler caves (13.0°C; Smith et al, 2021 ).…”

Wildlife Use of Anthropogenic Structures: A Comprehensive Review of Bridge Use by Bats

“…Similarly, Newman et al . (2021) discovered P. subflavus roosting on metal, ribbed sheets bolted to a bridge ceiling as well as on concrete I-beams. As seen in natural cave roosts, roost locations selected at bridges can vary between species, time of year, and seasonally.…”

Population structure and habitat preference of cave crickets (<i>Rhaphidophora</i> sp. (Orthoptera: Rhaphidophoridae)) in Sanghyang Kenit cave, Citatah karst area, West Java

“…Bats population in Sanghyang Kenit was distributed from twilight to dark zones, which generated guano piles on the cave floor. Commensurate with cave crickets, bats prefer humid and dark places for their roosting sites (Furey & Racey 2016;Lizarro et al 2020;Newman et al 2021). The measurement of soil pH showed that twilight and dark zones have more acidic pH than the entrance.…”