Assessing Cave Bat Populations

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White-nose syndrome (WNS) is an emergent fungal disease caused by Pseudogymnoascus destructans (Pd) that has caused the death of over 6 million bats since its initial detection in 2006. Pd has spread rapidly throughout the eastern United States and has been detected in both Alabama and Georgia, the two states bordering Florida. As WNS moves further south, the threat to Florida’s cave bats appears imminent. Gathering detailed information about current cave bat populations and their distribution before the arrival of WNS will allow Florida to better assess impacts that do occur, track the spread of WNS, and further develop WNS response actions.

Since 2014, FWC researchers have visited over 160 Florida caves to assess the status of cave-roosting bats prior to the arrival of WNS and to survey for signs of the disease. During each winter survey researchers examine bats for physical signs of the white Pd fungus on the nose, wings, ears and/or tail and look for dead or dying bats on the ground. A small subset of bats are held under a UV light to look for fluorescence of the Pd fungus on the wing membranes. Researchers also swab bats from caves considered to be at increased risk of infection (large numbers of bats or high levels of human visitation) and submit them to the USGS Wildlife Health Center for analysis. So far Florida appears to be WNS free, the only state east of the Mississippi River that can make this claim.

In addition to monitoring and surveillance efforts, FWC researchers are evaluating several other aspects of cave bat biology. Currently, we are assessing occupancy and abundance of cave bats to identify important hibernacula and monitor population trends. Researchers are also evaluating the role of cave structure, microclimate and landscape-level factors on the presence and abundance of bats using caves at winter roosts to better inform cave management activities. In addition, researchers are assessing the winter use of culverts by bats to determine if they provide important winter habitat, may potentially spread Pd in regions where caves are not present and could potentially function as WNS treatment sites. Lastly, we are using stable isotope analysis to determine the summering ground of bats to determine the potential influence of migration on disease transmission into the state.