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Fjelldal MA, Sørås R, Stawski C. Universality of torpor expression in bats. Physiol Biochem Zool 2022; 95:326-339. [DOI: 10.1086/720273] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Parker CA, Geiser F, Stawski C. Thermal physiology and activity in relation to reproductive status and sex in a free-ranging semelparous marsupial. CONSERVATION PHYSIOLOGY 2019; 7:coz073. [PMID: 31737272 PMCID: PMC6846706 DOI: 10.1093/conphys/coz073] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Revised: 06/26/2019] [Accepted: 08/21/2019] [Indexed: 06/10/2023]
Abstract
In a changing climate, southern hemisphere mammals are predicted to face rising temperatures and aridity, resulting in food and water shortages, which may further challenge already constrained energetic demands. Especially semelparous mammals may be threatened because survival of the entire population depends on the success of a single breeding event. One of these species, the yellow-footed antechinus, Antechinus flavipes, a small, heterothermic marsupial mammal, commences reproduction during winter, when insect prey is limited and energetic constraints are high. We examined the inter-relations between thermal and foraging biology of free-ranging A. flavipes and examined whether they use torpor for energy conservation, despite the fact that reproduction and torpor are considered to be incompatible for many mammals. Females used torpor during the reproductive season, but patterns changed with reproductive status. Prior to breeding, females used frequent (86% of days), deep and long torpor that was more pronounced than any other reproductive group, including pre-mating males (64% of days). Pregnant females continued to use torpor, albeit torpor was less frequent (28% of days) and significantly shorter and shallower than before breeding. Parturient and lactating females did not express torpor. During the mating period, males reduced torpor use (24% of days). Pre-reproductive females and pre-mating males were the least active and may use torpor to minimize predator exposure and enhance fat deposition in anticipation of the energetic demands associated with impending mating, gestation and lactation. Reproductive females were most active and likely foraged and fed to promote growth and development of young. Our data show that A. flavipes are balancing energetic demands during the reproductive season by modifying torpor and activity patterns. As the timing of reproduction is fixed for this genus, it is probable that climate change will render these behavioural and physiological adaptations as inadequate and threaten this and other semelparous species.
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Affiliation(s)
- Cassandra A Parker
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
| | - Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
| | - Clare Stawski
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW 2351, Australia
- Department of Biology, Norwegian University of Science and Technology, Trondheim 7491, Norway
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Geiser F, Bondarenco A, Currie SE, Doty AC, Körtner G, Law BS, Pavey CR, Riek A, Stawski C, Turbill C, Willis CKR, Brigham RM. Hibernation and daily torpor in Australian and New Zealand bats: does the climate zone matter? AUST J ZOOL 2019. [DOI: 10.1071/zo20025] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
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.
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Turbill C, Körtner G, Geiser F. Roost use and thermoregulation by female Australian long-eared bats (Nyctophilus geoffroyi and N. gouldi) during pregnancy and lactation. AUST J ZOOL 2019. [DOI: 10.1071/zo20036] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
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.
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Baloun DE, Guglielmo CG. Energetics of migratory bats during stopover: a test of the torpor-assisted migration hypothesis. J Exp Biol 2019; 222:jeb.196691. [DOI: 10.1242/jeb.196691] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 02/13/2019] [Indexed: 02/04/2023]
Abstract
The torpor-assisted migration hypothesis posits that migration is facilitated in bats by the use of torpor during stopover roosting periods, and predicts that at stopover bats regulate time in torpor facultatively so that daily energy expenditure is independent of ambient roosting temperature. Energy savings can thus be directed to migratory movement. However, direct measurements of total roosting energy expenditure in relation to ambient and body temperature are lacking. We captured migratory silver-haired bats (Lasionycteris noctivagans; ∼11g) at Long Point, Ontario, Canada in spring and fall 2016. We used quantitative magnetic resonance analysis to measure body composition change and energy expenditure over a twelve-hour roosting period in a ventilated incubator at 10, 17 and 25°C. We assessed the effects of season, body mass, sex and age on energy expenditure. We found that daily energy expenditure was independent of roosting temperature, and that this was achieved by flexible use of torpor. Variation in body mass at capture was driven mainly by differences in fat, and the amount of body fat was negatively related to torpor use, particularly in spring. Season, sex and age also affected torpor use and energy expenditure, notably with pregnant females being generally fatter and using less torpor than males in spring. We estimate that stopover contributes only 15-20% to the total energy costs of migration in bats compared to 70% or more in typical birds. This study provides support for the torpor-assisted migration hypothesis, and furthers our understanding of the energy budgets of migratory bats.
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Affiliation(s)
- Dylan E. Baloun
- Department of Biology, Advanced Facility for Avian Research, University of Western Ontario, London, Ontario, Canada
| | - Christopher G. Guglielmo
- Department of Biology, Advanced Facility for Avian Research, University of Western Ontario, London, Ontario, Canada
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Geiser F, Stawski C, Wacker CB, Nowack J. Phoenix from the Ashes: Fire, Torpor, and the Evolution of Mammalian Endothermy. Front Physiol 2017; 8:842. [PMID: 29163191 PMCID: PMC5673639 DOI: 10.3389/fphys.2017.00842] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 10/09/2017] [Indexed: 12/02/2022] Open
Affiliation(s)
- Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, Australia
| | - Clare Stawski
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, Australia
| | - Chris B Wacker
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, Australia
| | - Julia Nowack
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, Australia.,Department of Integrative Biology and Evolution, Research Institute of Wildlife Ecology, University of Veterinary Medicine Vienna, Vienna, Austria
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Black or white? Physiological implications of roost colour and choice in a microbat. J Therm Biol 2016; 60:162-70. [PMID: 27503729 DOI: 10.1016/j.jtherbio.2016.07.015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 07/15/2016] [Indexed: 12/16/2022]
Abstract
Although roost choice in bats has been studied previously, little is known about how opposing roost colours affect the expression of torpor quantitatively. We quantified roost selection and thermoregulation in a captive Australian insectivorous bat, Nyctophilus gouldi (n=12) in winter when roosting in black and white coloured boxes using temperature-telemetry. We quantified how roost choice influences torpor expression when food was provided ad libitum or restricted in bats housed together in an outdoor aviary exposed to natural fluctuations of ambient temperature. Black box temperatures averaged 5.1°C (maximum 7.5°C) warmer than white boxes at their maximum daytime temperature. Bats fed ad libitum chose black boxes on most nights (92.9%) and on 100% of nights when food-restricted. All bats used torpor on all study days. However, bats fed ad libitum and roosting in black boxes used shorter torpor and spent more time normothermic/active at night than food-restricted bats and bats roosting in white boxes. Bats roosting in black boxes also rewarmed passively more often and to a higher skin temperature than those in white boxes. Our study suggests that N. gouldi fed ad libitum select warmer roosts in order to passively rewarm to a higher skin temperature and thus save energy required for active midday rewarming as well as to maintain a normothermic body temperature for longer periods at night. This study shows that colour should be considered when deploying bat boxes; black boxes are preferable for those bats that use passive rewarming, even in winter when food availability is reduced.
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Jonasson KA, Guglielmo CG. Sex differences in spring migration timing and body composition of silver-haired batsLasionycteris noctivagans. J Mammal 2016. [DOI: 10.1093/jmammal/gyw119] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Stawski C, Körtner G, Nowack J, Geiser F. The importance of mammalian torpor for survival in a post-fire landscape. Biol Lett 2016; 11:20150134. [PMID: 26063748 DOI: 10.1098/rsbl.2015.0134] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Wildfires have increased in frequency and intensity worldwide with climate change as a main driving factor. While a number of studies have focused on population changes in regard to fires, there are essentially no quantitative data on behavioural and physiological adjustments that are vital for the persistence of individuals during and after fires. Here we show that brown antechinus, a small insectivorous marsupial mammal, (i) endured a prescribed fire in situ, (ii) remained in their scorched home range despite unburned areas nearby, and (iii) substantially increased post-fire torpor use and thus reduced foraging requirements and exposure to predators. Hence, torpor is a physiological adaptation that, although not quantified in this context previously, appears to play a key role in post-fire survival for this and other heterothermic species.
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Affiliation(s)
- Clare Stawski
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales 2351, Australia
| | - Gerhard Körtner
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales 2351, Australia
| | - Julia Nowack
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales 2351, Australia
| | - Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, New South Wales 2351, Australia
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Otto MS, Becker NI, Encarnação JA. Stage of pregnancy dictates heterothermy in temperate forest-dwelling bats. J Therm Biol 2014; 47:75-82. [PMID: 25526657 DOI: 10.1016/j.jtherbio.2014.11.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 11/19/2014] [Accepted: 11/19/2014] [Indexed: 10/24/2022]
Abstract
Bats face high energetic requirements, as powered flight is costly and they have a disadvantageous surface-to-volume-ratio. To deal with those requirements energy saving mechanisms, such as heterothermy (torpor), have evolved. Torpor during pregnancy, however, reduces rates of foetal development and consequently prolongs pregnancy. Therefore, heterothermy has a great effect on reproduction, as an unhindered parturition can only be assured by high body temperatures. Regardless of these adverse affects of torpor the energetic requirements of bats during reproduction urge for energy savings and bats are known to enter torpor during pregnancy. The species in the current study differ in their torpor patterns and thus their heterothermic strategy. However, we hypothesized, that species-specific heterothermic behaviour should be revoked at the end of pregnancy. We analyzed skin temperatures of Myotis bechsteinii, Myotis nattereri and Plecotus auritus during pregnancy and found no differences in torpor depth between species during the last phase of pregnancy. Furthermore, we could show that individuals entered torpor frequently during pregnancy and only minimized torpor during the last stage of pregnancy. This suggests that close to the end of pregnancy, heterothermy is restricted but not species-specific and the required energy is allocated otherwise.
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Affiliation(s)
- Matthias S Otto
- Mammalian Ecology Group, Department of Animal Ecology and Systematics, Justus-Liebig-University of Giessen, Heinrich-Buff-Ring 26, D-35392 Giessen, Germany.
| | - Nina I Becker
- Mammalian Ecology Group, Department of Animal Ecology and Systematics, Justus-Liebig-University of Giessen, Heinrich-Buff-Ring 26, D-35392 Giessen, Germany.
| | - Jorge A Encarnação
- Mammalian Ecology Group, Department of Animal Ecology and Systematics, Justus-Liebig-University of Giessen, Heinrich-Buff-Ring 26, D-35392 Giessen, Germany.
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McAllan BM, Geiser F. Torpor during reproduction in mammals and birds: dealing with an energetic conundrum. Integr Comp Biol 2014; 54:516-32. [PMID: 24973362 DOI: 10.1093/icb/icu093] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Torpor and reproduction in mammals and birds are widely viewed as mutually exclusive processes because of opposing energetic and hormonal demands. However, the reported number of heterothermic species that express torpor during reproduction is ever increasing, to some extent because of recent work on free-ranging animals. We summarize current knowledge about those heterothermic mammals that do not express torpor during reproduction and, in contrast, examine those heterothermic birds and mammals that do use torpor during reproduction. Incompatibility between torpor and reproduction occurs mainly in high-latitude sciurid and cricetid rodents, which live in strongly seasonal, but predictably productive habitats in summer. In contrast, torpor during incubation, brooding, pregnancy, or lactation occurs in nightjars, hummingbirds, echidnas, several marsupials, tenrecs, hedgehogs, bats, carnivores, mouse lemurs, and dormice. Animals that enter torpor during reproduction often are found in unpredictable habitats, in which seasonal availability of food can be cut short by changes in weather, or are species that reproduce fully or partially during winter. Moreover, animals that use torpor during the reproductive period have relatively low reproductive costs, are largely insectivorous, carnivorous, or nectarivorous, and thus rely on food that can be unpredictable or strongly seasonal. These species with relatively unpredictable food supplies must gain an advantage by using torpor during reproduction because the main cost is an extension of the reproductive period; the benefit is increased survival of parent and offspring, and thus fitness.
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Affiliation(s)
- B M McAllan
- *Department of Physiology, School of Medical Sciences and Bosch Institute, The University of Sydney, Sydney, New South Wales 2006, Australia; Centre for Behavioural and Physiological Ecology, Department of Zoology, University of New England, Armidale, New South Wales 2351, Australia*Department of Physiology, School of Medical Sciences and Bosch Institute, The University of Sydney, Sydney, New South Wales 2006, Australia; Centre for Behavioural and Physiological Ecology, Department of Zoology, University of New England, Armidale, New South Wales 2351, Australia
| | - Fritz Geiser
- *Department of Physiology, School of Medical Sciences and Bosch Institute, The University of Sydney, Sydney, New South Wales 2006, Australia; Centre for Behavioural and Physiological Ecology, Department of Zoology, University of New England, Armidale, New South Wales 2351, Australia
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Affiliation(s)
- C. Stawski
- Institute of Environmental Sciences; Jagiellonian University; Kraków Poland
- Centre for Behavioural and Physiological Ecology, Zoology; University of New England; Armidale NSW Australia
| | - C. K. R. Willis
- Department of Biology and Centre for Forest Interdisciplinary Research; University of Winnipeg; Winnipeg Canada
| | - F. Geiser
- Centre for Behavioural and Physiological Ecology, Zoology; University of New England; Armidale NSW Australia
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McAllan BM, Feay N, Bradley AJ, Geiser F. The influence of reproductive hormones on the torpor patterns of the marsupial Sminthopsis macroura: bet-hedging in an unpredictable environment. Gen Comp Endocrinol 2012; 179:265-76. [PMID: 22974513 DOI: 10.1016/j.ygcen.2012.08.024] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 08/23/2012] [Accepted: 08/24/2012] [Indexed: 11/30/2022]
Abstract
Seasonal cycles of reproduction are common in many mammals and these are combined with the necessary energy budgeting for thermoregulatory challenges. Many mammals meet the challenge of changing environmental temperatures in winter by using torpor, a controlled reduction in body temperature and metabolic rate. We aimed to determine the effects of photoperiod and reproductive hormones on the seasonal cycles of reproduction and torpor use in a marsupial that commences reproduction in winter, the stripe-faced dunnart, Sminthopsis macroura. Males and females were placed under LD 14:10 and natural reproductive hormones blocked by either flutamide (males) or mifepristone (females) or tamoxifen (females). Reproductive parameters, metabolic rate and torpor variables were determined. The same animals were then placed under LD 10:14 and given testosterone (males) or progesterone (females) or oestrogen (females). Reproductive parameters, metabolic rate and torpor variables were measured. Body mass and tail widths (fattening indicator) in males were significantly affected by testosterone, and the effects were reversed by hormone blockers. Reproductive parameters were unaffected. Resting metabolic rate and ability to use torpor were not affected by treatment in males, however torpor characteristics, especially torpor bout duration, were affected by presence of testosterone in males. In females, body mass was unaffected by hormone presence, although tail widths were affected. Disruption of reproductive cycles occurred with hormone blockers in females, however, resting metabolic rate was not affected, and only presence of progesterone affected torpor characteristics in females. Our results differ from those found for rodents, where presence of testosterone abolishes the use of torpor in males, and oestrogen inhibits torpor use in females. Our study suggests that, in this mammal, metabolic responses to the presence or absence of reproductive hormones differs between males and females, and there is no absolute endocrinologically-driven reproductive season demarcated from the torpor season.
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Affiliation(s)
- B M McAllan
- Physiology, School of Medical Sciences, and Bosch Institute, The University of Sydney, NSW 2006, Australia.
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Downs C, Zungu M, Brown M. Seasonal effects on thermoregulatory abilities of the Wahlberg's epauletted fruit bat (Epomophorus wahlbergi) in KwaZulu-Natal, South Africa. J Therm Biol 2012. [DOI: 10.1016/j.jtherbio.2011.12.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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