Evidence of Latitudinal Migration in Tri-colored Bats, Perimyotis subflavus

Abstract

BackgroundAnnual movements of tri-colored bats (Perimyotis subflavus) are poorly understood. While this species has been considered a regional migrant, some evidence suggests that it may undertake annual latitudinal migrations, similar to other long distance North American migratory bat species.Methodology/Principal FindingsWe investigated migration in P. subflavus by conducting stable hydrogen isotope analyses of 184 museum specimen fur samples and comparing these results (δDfur) to published interpolated δD values of collection site growing season precipitation (δDprecip). Results suggest that the male molt period occurred between June 23 and October 16 and 33% of males collected during the presumed non-molt period were south of their location of fur growth. For the same time period, 16% of females were south of their location of fur growth and in general, had not travelled as far as migratory males. There were strong correlations between δDfur from the presumed molt period and both growing season δDprecip (males – r 2 = 0.86; p<0.01; females – r 2 = 0.75; p<0.01), and latitude of collection (males – r 2 = 0.85; p<0.01; females – r 2 = 0.73; p<0.01). Most migrants were collected at the northern (>40°N; males and females) and southern (<35°N; males only) extents of the species' range.Conclusions/SignificanceThese results indicate a different pattern of migration for this species than previously documented, suggesting that some P. subflavus engage in annual latitudinal migrations and that migratory tendency varies with latitude and between sexes. We suggest that this species' hibernation ecology makes it particularly susceptible to long winters, making migration from the northern extent of the species' range to more southern hibernacula preferable for some individuals. Fur δD values for some of the northern individuals may indicate an increase in the currently accepted northern range of this species. Sex-biased differences in migration may be the result of differences in reproductive pressures.

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

“…This timing of molt is similar to that observed in other bat species (Cryan et al 2012, Fraser et al 2012, Fraser et al 2013). Thus, fur collected along the migratory route is fur grown on the summering grounds during the current year's molt.…”

“…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. We considered variables to be nonnormal if P , 0.05, but if the W statistic was sufficiently close to one (i.e., !…”

“…Combining this relationship with capture and museum records demonstrated that some hoary bats migrate long-distances (.2000 km; Cryan et al 2004). Further studies have attempted to evaluate the use of stable-isotope analysis to assign origins to individuals of various bat species across Europe , the eastern United States (Britzke et al 2009, Sullivan et al 2012, and Canada (Fraser et al 2012 (Britzke et al 2009). Given the difficulty in studying bat migration, the ability to use endogenous markers, such as stable isotopes, offers a feasible alternative to more traditional but inefficient methods (i.e., banding or radiotracking).…”

Questions, ideas and tools: lessons from bat echolocation

“…Isotope analysis has provided evidence of long-distance migration by some bats (Cryan et al 2004;Fraser et al 2012) and has raised questions about their flight patterns ) and physiology (McGuire et al 2013). This leaves unanswered questions about what cues migratory and other bats use in large-scale navigation, perhaps the lure that originally drew Griffin to bats.…”

Moulting matters: the importance of understanding moulting cycles in bats when using fur for endogenous marker analysis

“…The use of endogenous markers to study migration has many benefits, including the requirement for only a small tissue sample that is usually collected nonlethally and the need to capture the study animal only once. Given the challenges inherent in capturing and tracking many species of bats, these techniques are promising for future bat research, and there are already many examples of studies using stable isotope analyses to study bat migration (Fleming et al 1993;Cryan et al 2004;Fraser et al 2010;Erzberger et al 2011;Britzke et al 2012;Fraser et al 2012;Ossa et al 2012;Popa-Lisseanu et al 2012;Sullivan et al 2012;Voigt et al 2012a). Fewer studies have examined trace element or strontium isotope compositions in bat tissues (but see Hickey et al 2001;Allinson et al 2006;Gashchak et al 2010;Ghanem et al 2013).…”