Winter climate affects torpor patterns and roost choice in New Zealand lesser short‐tailed bats

Variation in winter conditions differentially impacts thermoregulation of endotherms, with some species using torpor as an energy‐saving strategy during periods of negative energy balance. We evaluated how differences in energy balance due to winter ambient temperatures ( T a ) , would lead to differing torpor expression and roost choice between populations. Here, we monitored T a and skin temperatures ( T sk ) of New Zealand lesser short‐tailed bats ( Mystacina tuberculata) using temperature telemetry from an inland population from Pureora, North Island and another from Hauturu/Little Barrier Island (Hauturu), an offshore island. Relative to Pureora, all recorded T a variables were higher in Hauturu. Hauturu bats used short torpor (<24 h) more frequently (51% of observational days) than their Pureora conspecifics (33%). Furthermore, minimum T sk of Hauturu bats correlated positively with mean T a and Hauturu bats were more likely to arouse on nights with warmer sunset T a . No correlation was found for Pureora bats. Torpor bout duration did not differ between sites. On Hauturu, bats preferred thermally unstable roosts and preferentially roosted inside dead punga/silver fern‐trees ( Cyathea dealbata ). As punga thermal characteristics did not differ from T a , Hauturu bats may take advantage of warm T a to reduce rewarming costs. We did not observe differences in any thermoregulatory variables between sexes in Hauturu. Differences in winter T a may differentially impact populations across a latitudinal gradient. Although bat populations in warmer climates are under less thermoregulatory stress, site and climate specific adaptations appear to be employed that affect roost choice and torpor patterns.