Thermal behaviour of lesser short-tailed bats (Mystacina tuberculata)

Zenon Czenze

Many clades of vertebrates employ “torpor” (a physiological state characterized by drastically lowered metabolic rate and body temperature) as a strategy to avoid severe environmental conditions, conserve energy when food is scarce or unpredictable and reduce energy requirements (Wang, 1989, Grigg et al., 2004, Geiser, 2004). Rates of metabolism during torpor are typically less than 3% of euthermic rates at the same ambient temperature (Ta)

(Speakman & Rowland, 1999). The duration and depth of this torpor is highly variable between species, sexes, and individuals.

New Zealand provides a unique opportunity to study effects of a subtropical to temperate latitudinal gradient on torpor expression as it ranges from cold-temperate and sub-alpine/alpine with Ta as low as -10 °C in winter in the south to sub-tropical in the north. New Zealand is also home to lesser short-tailed bats (Mystacina tuberculata), an endemic and threatened bat species which provides a good opportunity to assess torpor expression in the wild. This species roosts communally ranging up to thousands of individuals (Sedgley, 2001), and many similar tree-roosting bats of the same family employ torpor to reduce thermoregulatory costs especially during pregnancy, relative to lactation (Willis et al., 2006). However, to date no work has examined torpor expression in New Zealand bats, despite its likely importance for roost requirements, survival and fitness.

This project will be the first to examine the potential heterothermic behaviour of M. tuberculata and will shed light on crucial aspects of this threatened animal’s life history. Additionally, this project will lead to exciting breakthroughs about the influence of and interactions between climate, reproductive status, Ta, and prey availability on torpor expression in free- ranging endotherms.