Acceptance of bats to gates at abandoned mines

Abstract

Caves and abandoned mines provide roosting habitat for bat species that depend on subterranean conditions. Disturbances at caves (e.g., commercial development, recreation) limit their availability to bats, in some cases shifting use to abandoned mines. However, abandoned mines pose public safety hazards and often are gated to reduce risk to humans while maintaining access to bats. To date there is limited information on species‐specific acceptance of gates at abandoned mines. We designed our research objectives to determine short‐term (1 week) behavioral responses of bats to gating, including gate material and height above ground, mid‐term (<1 yr) changes in bat use before and after gate installation, and long‐term changes (≥4 yrs) in use and factors influencing species presence. We used an in situ mock gate experiment, comparison of bat use before and after gating, and genetic identification of guano in gated mines for our short‐, mid‐, and long‐term studies, respectively. In our short‐term study, bats increased energetically demanding behaviors following gate installation. Although we detected no difference in responses to gate material or height, a less maneuverable bat species circled, collided, and landed more frequently on gates than did an agile species. In the mid‐term study, activity remained stable or increased at 73% of mines after gating compared to before gating, although number of maternity colonies decreased. In the long‐term study, elevation, portal area, number of mine levels, and entrances were more important than gates in predicting presence of 4 bat species, including 2 subterranean obligates. Species‐specific responses to gates appeared based on morphology and vocalization characteristics. Responses to gates shifted from negative in our short‐term study to positive in our long‐term study. Gate age and mine characteristics were more important predictors of use for most species than gate design. Although the complexity of subterranean habitats makes them difficult to replicate and many factors may influence how bats use this habitat, gates designed for bats (bat‐compatible) appear effective for many species. © 2018 The Wildlife Society.

A fecal sequel: Testing the limits of a genetic assay for bat species identification

“…While T . brasiliensis has been readily detected in lab and field scenarios with this marker and analysis pathway [3, 24], this study’s suggestion of a primer bias against T . brasiliensis DNA when it is rare suggests that additional samples may be required for studies in which detection of mollosids is critical, such as for endangered species.…”

“…To demonstrate the large-scale utility of our approach in screening roosts for presence of bat species, we collected guano from 41 abandoned mines in the U.S. Southwest (Arizona, Colorado, Nevada, New Mexico, and Utah) at elevations ranging from 331 to 2,495 m [24]. Abandoned mines in this region outnumber natural caves and are commonly used by bats as roosting habitat [33].…”

“…We targeted guano pellets that were whole and not disintegrating. Additional collection methods and site details are presented in [24]. We stored samples at 80°C until DNA extraction.…”

“…Users have included U.S. state and federal agencies (e.g., the National Park Service, Forest Service, Bureau of Land Management, state wildlife management departments, Departments of Transportation, Department of Agriculture, Department of Defense), non-governmental organizations, environmental consulting firms, and universities [23–25]. This assay, in addition to identifying bat species that use particular roosts [25], has also been employed to confirm visual identifications of captured bats [23], identify bat carcasses at windfarms, screen fertilizer to determine the species that contributed guano, detect nectar-feeding bats from saliva on agave flowers, and evaluate the effects of gates on bat use of mines [24].…”

A review of the major threats and challenges to global bat conservation

“…Installing bat‐friendly gates that permit bats to continue to use caves or mines while limiting human access can reduce disturbance to bats and increase use and colony size of bats for some species and regions . Some species may be intolerant of gating structures and installation should be tested and bat use monitored prior to wide‐scale implementation to ensure that gating leads to roost protection rather than abandonment . Gating may also require education and communication efforts to target audiences, such as recreational users, or the gates may be destroyed.…”