Analysis of Stable Isotopes of Hydrogen to Determine Migrational Source of Silver-Haired Bats (Lasionycteris noctivagans) in Alabama

Abstract

Signatures of deuterium obtained from claws of 21 silver-haired bats (Lasionycteris noctivagans) were used to estimate the nearest probable pre-migratory location of these bats. For 5 consecutive weekends beginning 28 September 2007, bats were captured in mist nets at Walls of Jericho and near Paint Rock, Jackson Co., Alabama. In addition to the 21 silver-haired bats, 2 hoary bats (Lasiurus cinereus) and 2 big brown bats (Eptesicus fuscus) were preserved as museum specimens. Claw, wing, feces, and hair samples were taken from 1 big brown bat and 2 silver-haired bats (1 male and 1 female) for comparison between species. Mean value of signatures of deuterium in claws of silver-haired bats was -87.07‰ (SE = 14.67). I used GIS maps of the distribution of stable isotopes of hydrogen to determine estimates of distance traveled during migration using signatures of hydrogen isotopes. Data from analysis of stable isotopes support previous observations that silver-haired bats are migratory and provide evidence that they migrate great distances, possibly >1,600 km. There was a significant interaction of sex by night captured on signatures of deuterium (F2,20 = 5.7, P = 0.022). One-way ANOVAs revealed no difference between sexes (F1,20 < 0.001, P = 0.998) or night of capture (F7,20 = 0.46, P = 0.846) indicating no sex-specific differences in migration patterns or time-dependent variation in those patterns. Preliminary comparisons between 2 specimens of silver-haired bats and 1 big brown bat for claw, wing, hair, and fecal samples indicated that claws may be the best tissue to use for analysis of stable isotopes in studies of long-distance dispersal, and that male and female silver-haired bats may molt at different times; however a larger sample is needed to fully elucidate these relationships.