New take on a decades-old technique: the applications of ⁸⁷Sr/⁸⁶Sr and δ²H to establish patterns in migration and dispersal of terrestrial wildlife species

A thorough body of literature establishes the use of intrinsic marking techniques for studying continent scale, seasonal migrations of organisms. However, there is great potential for these techniques to infer movements across a smaller landscape and greater range of timescales than previously demonstrated. Here, we used multiple tissues (bones, teeth, fur) and several isotopic systems (δ²H, δ³⁴S, ⁸⁷Sr/⁸⁶Sr) to predict seasonal and lifetime movements of Myotis lucifugus in Newfoundland, Canada. Using regional ⁸⁷Sr/⁸⁶Sr estimates calculated from the fur of known origin individuals, we inferred movements of unknown origin individuals relative to three geologically distinct regions. Additionally, although the δ³⁴S results were inconclusive, using a newly developed δ²H in precipitation (δ²Hp) isoscape, we determined probabilistic summer residency locations for the same individuals. These inferences and predictions, combined with the absolute difference between ⁸⁷Sr/⁸⁶Sr values of teeth and bones (|⁸⁷Sr/⁸⁶SrT-⁸⁷Sr/⁸⁶SrB|), provided evidence that M. lucifugus in Newfoundland exhibit a high rate of migratory movements within and between regions, but rarely disperse on the regional level, and don’t appear to have sex-biased dispersal. Employing these results as a case study, we establish the potential for these techniques to illuminate many unanswered questions related to migratory theory and the protection of imperiled species.