Continental‐scale, seasonal movements of a heterothermic migratory tree bat

Abstract

Long-distance migration evolved independently in bats and unique migration behaviors are likely, but because of their cryptic lifestyles, many details remain unknown. North American hoary bats (Lasiurus cinereus cinereus) roost in trees year-round and probably migrate farther than any other bats, yet we still lack basic information about their migration patterns and wintering locations or strategies. This information is needed to better understand unprecedented fatality of hoary bats at wind turbines during autumn migration and to determine whether the species could be susceptible to an emerging disease affecting hibernating bats. Our aim was to infer probable seasonal movements of individual hoary bats to better understand their migration and seasonal distribution in North America. We analyzed the stable isotope values of non-exchangeable hydrogen in the keratin of bat hair and combined isotopic results with prior distributional information to derive relative probability density surfaces for the geographic origins of individuals. We then mapped probable directions and distances of seasonal movement. Results indicate that hoary bats summer across broad areas. In addition to assumed latitudinal migration, we uncovered evidence of longitudinal movement by hoary bats from inland summering grounds to coastal regions during autumn and winter. Coastal regions with nonfreezing temperatures may be important wintering areas for hoary bats. Hoary bats migrating through any particular area, such as a wind turbine facility in autumn, are likely to have originated from a broad expanse of summering grounds from which they have traveled in no recognizable order. Better characterizing migration patterns and wintering behaviors of hoary bats sheds light on the evolution of migration and provides context for conserving these migrants.

Origins and migratory patterns of bats killed by wind turbines in southern Alberta: evidence from stable isotopes

“…Our data show that migratory bats killed in southwestern Alberta may come from forests hundreds of kilometers away and potentially from large catchment areas, as was recently reported in the European study by Voigt et al (2012) and a North American study by Cryan et al (2014). Thus, the impacts of these fatalities may have broad-reaching ecological consequences.…”

“…To investigate the summer distribution and Cryan et al (2014) to assign a likelihood of geographic origin. To geographically assign individuals using IsoMAP, d…”

“…For hoary bats, we used the relationship published by Cryan et al (2014). However, there is no published relationship for silver-haired bats, so we examined both the Cryan et al (2014) relationship and the relationship published by Popa-Lisseanu et al (2012).…”

“…For hoary bats, we used the relationship published by Cryan et al (2014). However, there is no published relationship for silver-haired bats, so we examined both the Cryan et al (2014) relationship and the relationship published by Popa-Lisseanu et al (2012). The latter relationship is based on multiple species of European bats, presumably making it more universal than other, more species-specific equations (e.g., Britzke et al 2009, Fraser et al 2012 We used Shapiro-Wilk W tests to test for normality.…”

“…Stable-isotope analysis of bat tissue has been used in numerous dietary studies (Fleming et al 1993, Voigt and Kelm 2006, Popa-Lisseanu et al 2007, Painter et al 2009, Cryan et al 2012, and also to investigate the origins and migratory movements of bats. (Cryan et al 2004, Cryan et al 2014. Combining this relationship with capture and museum records demonstrated that some hoary bats migrate long-distances (.2000 km; Cryan et al 2004).…”