First Direct Evidence of Long-distance Seasonal Movements and Hibernation in a Migratory Bat.

Theodore J Weller,Michael R Schirmacher,Cris D Hein,Felix Liechti,Kevin T Castle,Paul M Cryan

doi:10.1038/srep34585

Abstract

Understanding of migration in small bats has been constrained by limitations of techniques that were labor-intensive, provided coarse levels of resolution, or were limited to population-level inferences. Knowledge of movements and behaviors of individual bats have been unknowable because of limitations in size of tracking devices and methods to attach them for long periods. We used sutures to attach miniature global positioning system (GPS) tags and data loggers that recorded light levels, activity, and temperature to male hoary bats (Lasiurus cinereus). Results from recovered GPS tags illustrated profound differences among movement patterns by individuals, including one that completed a >1000 km round-trip journey during October 2014. Data loggers allowed us to record sub-hourly patterns of activity and torpor use, in one case over a period of 224 days that spanned an entire winter. In this latter bat, we documented 5 torpor bouts that lasted ≥16 days and a flightless period that lasted 40 nights. These first uses of miniature tags on small bats allowed us to discover that male hoary bats can make multi-directional movements during the migratory season and sometimes hibernate for an entire winter.

Highlights

Individuals of several species of North American bats make biannual migratory journeys between winter and summer habitat[1], yet compared to birds, our understanding of the details and destinations is nascent
We obtained 2, 4, and 6 global positioning system (GPS) fixes per bat that were recorded during October 2014
GPS tags allowed us to determine that some individuals make long distance, multi-directional movements during autumn while data loggers allowed us to demonstrate that hoary bats can engage in winter-long hibernation

Summary

Introduction

Individuals of several species of North American bats make biannual migratory journeys between winter and summer habitat[1], yet compared to birds, our understanding of the details and destinations is nascent. We attached data loggers that recorded light level, temperature, and activity, from which we obtained detailed information on individual hoary bats over periods spanning as long as an entire winter. These data recorded from small, free-ranging, migratory tree bats are the first of their kind and allow us to challenge two assumptions about hoary bats: (1) that their autumn migration routes are directional and generally linear and (2) that, unlike smaller cave-dwelling bats, they do not hibernate or use sequential bouts of multi-day torpor during winter

Methods

Results

Conclusion