Abstract
Most North American bats undertake seasonal migrations and many aspects of bat migration are not well documented. Stable isotope analyses of animal tissues can elucidate migratory origin, but this technique has not been widely applied to bats. The objectives of this dissertation were i) to investigate North American bat migration using stable isotope analyses of fur and ii) to highlight some of the strengths and weaknesses of this analytical technique when applied to bat systems. I conducted stable hydrogen (δD), carbon (δ13C), and nitrogen (δ15N) isotope analyses on fur samples from five bat species.
First, I documented δDfur heterogeneity in summer resident populations of little brown bats (Myotis lucifugus), eastern red bats (Lasiurus borealis), hoary bats (Lasiurus cinereus) and silver-haired bats (Lasionycteris noctivagans). In some species, δDfur composition varied systematically within and among individual bats, age groups, species, sites, and over time. Future investigations should standardize fur collection according to the above variables and data from multiple species should not be pooled. Bats from proximate colonies can be discriminated using multiple stable isotopes and stable isotope correlations existed in some species. Multi-isotope studies may be used to detect population mixing.
Second, I investigated the origins of fall migrant L. noctivagans and L. borealis passing through an Ontario migration monitoring station. There was no stable isotope evidence that migrant L. noctivagans originated from a wide range of latitudes, or that latitudinal origin varied with time or migrant “wave”. Lasiurus borealis stable isotope results were variable between years and further work is required before stable isotope results can be used to draw ecological conclusions about this species.
Third, I investigated the annual migratory movements of tri-colored bats (Perimyotis subflavus), a presumed regional migrant. Stable hydrogen isotope results indicated that >30% of males migrated south in the fall. Only 16% of females migrated south and their movements were shorter than the male movements. Most of the migrants were captured at the northern and southern extremes of the species’ range. I concluded that these bats engage in a pattern of partial and differential latitudinal migration that has previously not been described for this species.