Winter torpor and activity patterns of a fishing bat (Myotis macropus) in a mild climate

Small insectivorous bats often enter a state of torpor, a controlled, reversible decrease in body temperature and metabolic rate. Torpor provides substantial energy savings and is used more extensively during periods of low temperature and reduced prey availability. We studied torpor use and activity of a small (10.1 ± 0.4 g) fishing bat, Myotis macropus, during winter in a mild climate in Australia. We predicted that the thermal stability of water would make foraging opportunities in winter more productive and consistent in a riparian habitat compared to a woodland habitat, and therefore, fishing bats would use torpor less than expected during winter compared to other bats. Using temperature-sensitive radio transmitters, we recorded the skin temperature of 12 adult (6 M, 6 F) bats over 161 bat-days (13.4 ± 5.4 days per bat) during Austral winter (late May to August), when daily air temperature averaged 6.2–18.2°C. Bats used torpor every day, with bouts lasting a median of 21.3 h and up to 144.6 h. Multiday torpor bouts were more common in females than males. Arousals occurred just after sunset and lasted 3.5 ± 2.9 h. Arousals tended to be longer in males than females and to occur on warmer evenings, suggesting some winter foraging and perhaps male harem territoriality or other mating-related activity was occurring. The extensive use of torpor by M. macropus during relatively mild winter conditions when food is likely available suggests torpor might function to minimize the risks of mortality caused by activity and to increase body condition for the upcoming breeding season.

Light pollution: a landscape-scale issue requiring cross-realm consideration

Terrestrial, marine and freshwater realms are inherently linked through ecological, biogeochemical and/or physical processes. An understanding of these connections is critical to optimise management strategies and ensure the ongoing resilience of ecosystems. Artificial light at night (ALAN) is a global stressor that can profoundly affect a wide range of organisms and habitats and impact multiple realms. Despite this, current management practices for light pollution rarely consider connectivity between realms. Here we discuss the ways in which ALAN can have cross-realm impacts and provide case studies for each example discussed. We identified three main ways in which ALAN can affect two or more realms: 1) impacts on species that have life cycles and/or stages in two or more realms, such as diadromous fish that cross realms during ontogenetic migrations and many terrestrial insects that have juvenile phases of the life cycle in aquatic realms; 2) impacts on species interactions that occur across realm boundaries, and 3) impacts on transition zones or ecosystems such as mangroves and estuaries. We then propose a framework for cross-realm management of light pollution and discuss current challenges and potential solutions to increase the uptake of a cross-realm approach for ALAN management. We argue that the strengthening and formalisation of professional networks that involve academics, lighting practitioners, environmental managers and regulators that work in multiple realms is essential to provide an integrated approach to light pollution. Networks that have a strong multi-realm and multi-disciplinary focus are important as they enable a holistic understanding of issues related to ALAN.

Bat research in Australasia – in memory of Les Hall

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