Little Brown Bats (Myotis lucifugus): ecology of a White-nosed syndrome affected population.

Abstract

White-nose syndrome (WNS) is currently classified as an emerging disease, caused by the fungus, Geomyces destructans, currently affecting hibernating bats across the Appalachian range, into Canada and locations in the Midwest (USGS, 2011). The effects of the disease have been devastating, with bats at infected sites showing 87-95% mortality and complete loss of populations in some caves (Blehert, 2009, Frick, 2010). One of the most significant findings to date is that WNS affected bats exhibit depleted white and brown fat reserves by mid-winter and, although this is not the causal factor for development of WNS, it has been found to be the ultimate cause of bat death in affected hibernacula (Blehert, et al. 2009). In addition, studies have found that bats in White-Nose syndrome areas may be entering hibernation with lower stores of body fat, predisposing them to starvation when affected by G. destructans (Kunz, 2009). The Chautauqua Institution (CI), Chautauqua, NY is home to approximately 5,000 little brown bats (Myotis lucifugus) in maternity colonies occupying the attics and crawlspaces of the 750, lakeside seasonal homes and buildings there (Neilson, 1991, Syme, 2001, this study). The population is assumed to be affected by White-Nose syndrome since approximately 30% of the bats captured from two of the colonies during the summer of 2010 exhibited White-nose syndrome type wing damage and the fungus was identified in hibernacula approximately 75 km from the (CI) the preceding winter, 2009-2010 (USGS, 2011). However, this population appears to be stable, although affected by WNS. We studied the feeding-ecology of this population to determine if there were factors contributing to increased survival in WNS affected bats that reside at the CI. We found that preferred prey (Diptera) numbers were more than adequate for reproduction and pre-hibernation fat deposition and were not affected by either precipitation levels or ambient temperature. We also found that bats exhibiting WNS type wing damage did not have significantly different body mass indices (BMI's) than their unaffected conspecifics. Bats at the CI have maintained BMI in comparison to historical data. This combined with an abundance of roosts may contribute to the stability of a WNS affected population.-- (leaf 2) The capture of large numbers of bats from given populations has been a challenge since bat trapping schemes were first devised. The two most commonly employed devices are the harp trap, utilizing a series of parallel wires to disrupt bats in flight and mist nets, borrowed from avian research, that function to entangle bats that contact it while in flight. Modifications to both have been made to increase their efficiency but both still suffer from relatively low capture rates, and can be cumbersome to use. We have constructed and utilized a trap for bats that has capture rates of between 80 and 100% when deployed at the entrances to maternity roosts of little brown bats (Myotis lucifugus). Our trap incorporates a mechanism for detaching the bag holding captured bats and attaching a new bag so that trapping can continue uninterrupted while processing of captured bats can begin. Using this trap we were able to capture 456 bats in one evening using 4 holding bags in succession. The principles used in the angle trap could be applied to larger, megachiropteran species as well as more open environments, such as flyways and feeding sites. -- (leaf 36)