Migration, Diet, or Molt? Interpreting Stable‐Hydrogen Isotope Values in Neotropical Bats

Abstract

ABSTRACTMigratory behavior in bats is poorly described, particularly in the Neotropics. Stable‐hydrogen isotope (δD) analysis may allow tracking of altitudinal movements of bats but has not been explored. δD values in rainwater (δDp) deplete linearly with altitude and are reflected in the keratinous tissues of animals through diet. A mismatch between keratin δD (δDk) and that expected at the capture site based on δDp can indicate prior migration. We collected rainwater, claws and hair from eight bat species at two lower‐montane forest sites in Nicaragua. Claw δD for Carollia brevicauda and hair and claws for Desmodus rotundus (known to be non‐migratory) fell within the predicted range based on rainwater (−17 to −60‰) suggesting these tissues were synthesized at the study site. δD tissue values for Artibeus toltecus, Sturnira lilium, Glossophaga soricina, Anoura geoffroyi, and hair for C. brevicauda were more negative than predicted for the capture site (−60‰) suggesting tissue synthesis at higher elevation and migration downslope to the capture site. However, our study area represents the highest elevation in the region; the nearest appropriate higher elevations are 350–500 km away and seasonal migration is expected to be<200 km. Thus we consider that seasonal shifts in δDp (9 to −45‰) may result in differences in species which molt at different times, and that diet may have driven differences in δD. Our results suggest that the effects of molt timing and diet may first need to be understood before δD may be successfully used to track bat movements.