Now showing 1 - 3 of 3
  • Publication
    Roost use and thermoregulation by female Australian long-eared bats (Nyctophilus geoffroyi and N. gouldi) during pregnancy and lactation
    Small insectivorous bats commonly use torpor while day-roosting, even in summer. However, reproductive female bats are believed to benefit from avoiding torpor because a constant, elevated body temperature maximises the rate of offspring growth, which could increase offspring survival. We used temperature-sensitive radio-transmitters to locate roosts and document the thermal biology of pregnant and lactating females of Nyctophilus geoffroyi (9 g) and N. gouldi (11 g) at a woodland in a cool temperate climate. Unlike males, reproductive female Nyctophilus spp. roosted as small groups (<25) within insulated tree cavities. Roost switching occurred every 3.7 ± 1.5 (N. geoffroyi) or 1.7 ± 0.8 days (N. gouldi), and radio-tagged individuals roosted together and apart on different days. Skin temperature during roosting was most often between 32 and 36°C, and torpor was used infrequently. Male Nyctophilus have been shown in previous studies to use torpor daily during summer. These contrasting torpor patterns likely reflect the warmed cavities occupied by maternity colonies and the thermally unstable shallow crevices occupied by individual males. Our results support the hypothesis that availability of thermally suitable roosts will influence thermoregulatory patterns of reproductive females and hence the growth rates and survival of their offspring. Thus, it is important to conserve woodland habitat with trees in a range of decay stages to provide opportunities for selection and movement among roost trees by reproductive female bats.
  • Publication
    Hibernation and daily torpor in Australian and New Zealand bats: does the climate zone matter?
    (CSIRO Publishing, 2019) ;
    Bondarenco, Artiom
    ;
    Currie, Shannon E
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    ; ;
    Law, Bradley S
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    ;
    Riek, Alexander
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    ; ;
    Willis, Craig K R
    ;
    Brigham, R Mark

    We aim to summarise what is known about torpor use and patterns in Australian and New Zealand (ANZ) bats from temperate, tropical/subtropical and arid/semiarid regions and to identify whether and how they differ. ANZ bats comprise ~90 species from 10 families. Members of at least nine of these are known to use torpor, but detailed knowledge is currently restricted to the pteropodids, molossids, mystacinids, and vespertilionids. In temperate areas, several species can hibernate (use a sequence of multiday torpor bouts) in trees or caves mostly during winter and continue to use short bouts of torpor for the rest of the year, including while reproducing. Subtropical vespertilionids also use multiday torpor in winter and brief bouts of torpor in summer, which permit a reduction in foraging, probably in part to avoid predators. Like temperate-zone vespertilionids they show little or no seasonal change in thermal energetics during torpor, and observed changes in torpor patterns in the wild appear largely due to temperature effects. In contrast, subtropical blossom-bats (pteropodids) exhibit more pronounced daily torpor in summer than winter related to nectar availability, and this involves a seasonal change in physiology. Even in tropical areas, vespertilionids express short bouts of torpor lasting ~5 h in winter; summer data are not available. In the arid zone, molossids and vespertilionids use torpor throughout the year, including during desert heat waves. Given the same thermal conditions, torpor bouts in desert bats are longer in summer than in winter, probably to minimise water loss. Thus, torpor in ANZ bats is used by members of all or most families over the entire region, its regional and seasonal expression is often not pronounced or as expected, and it plays a key role in energy and water balance and other crucial biological functions that enhance long-term survival by individuals.

  • Publication
    Ecology and thermal physiology of an insectivorous bat restricted to subtropical and tropical Australia
    Bats of the mammalian order Chiroptera make up about one-fifth of all mammal species and a large proportion of bat species inhabit subtropical and tropical regions. Most bats, particularly microchiropterans, weigh well under 25 g and therefore expend large amounts of energy for normothermic thermoregulation. Consequently, many microchiropterans are heterothermic endotherms and use torpor for energy conservation. However, despite the large number of species inhabiting subtropical and tropical regions knowledge about torpor use in free-ranging subtropical and tropical microbats is scarce. This is largely due to the view that low and stable ambient temperatures (Ta) are necessary for torpor use. The aim of my project was to collect data on the skin temperature (Tskin) of free-ranging insectivorous northern long-eared bats ('Nyctophilus bifax'), which are restricted to the Australian tropics and subtropics. This was accomplished via temperature-telemetry. As weather, food availability and reproduction vary seasonally, I undertook seasonal studies on 'N. bifax' at a subtropical field site, because detailed knowledge on how free-ranging subtropical insectivorous bats cope with such changes is essentially non-existent. Winter studies were undertaken on 'N. bifax' in two different habitats, a subtropical region near the southern end of their range and a tropical region near the northern end of their range to determine whether they employ torpor and especially prolonged torpor, and also whether their thermal physiology varies within their range. Additionally, since few studies have examined the thermal energetics of torpor in species that inhabit only subtropical and tropical regions, I quantified the thermal energetics of 'N. bifax' during summer, winter and spring from a subtropical habitat and also during winter from a tropical habitat.