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Stawski C, Simmonds EG. Contrasting physiological responses to habitat degradation in two arboreal mammals. iScience 2021; 24:103453. [PMID: 34988391 PMCID: PMC8710554 DOI: 10.1016/j.isci.2021.103453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 10/14/2021] [Accepted: 11/11/2021] [Indexed: 11/19/2022] Open
Abstract
To cope with the challenges presented by habitat degradation and loss, animals must often respond by adjusting physiological and behavioral mechanisms. Here we quantified physiological and behavioral traits, including body temperature and food consumption, of two mammals with differing thermoregulatory strategies in response to changes in climate and habitat. We show that both species responded to challenging climatic conditions by increasing torpor use to save energy, yet their responses were impacted by varying vegetation levels. Sugar gliders decreased torpor use in a dense habitat likely due to a signal of greater food production and protection from predators. Conversely, eastern pygmy possums employed more torpor perhaps to build up fat reserves in anticipation of leaner times. Indeed, in dense habitat eastern pygmy possums did not alter food intake yet showed an increase in body mass, whereas sugar gliders consumed less food and lost body mass, revealing the large energetic savings provided by torpor. Physiological responses to habitat degradation differ among mammals Hibernating eastern pygmy possums employ less torpor in degraded habitat Whereas sugar gliders, daily heterotherms, employ more torpor in degraded habitat These differing responses are perhaps due to perceived predation risk
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Affiliation(s)
- 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, 7491 Trondheim, Norway
- Corresponding author
| | - Emily G. Simmonds
- Department of Mathematical Sciences and Centre for Biodiversity Dynamics, Norwegian University of Science and Technology, 7491 Trondheim, Norway
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2
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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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Hume T, Geiser F, Currie SE, Körtner G, Stawski C. Responding to the weather: energy budgeting by a small mammal in the wild. Curr Zool 2019; 66:15-20. [PMID: 32467700 PMCID: PMC7245004 DOI: 10.1093/cz/zoz023] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 05/02/2019] [Indexed: 11/12/2022] Open
Abstract
Energy conservation is paramount for small mammals because of their small size, large surface area to volume ratio, and the resultant high heat loss to the environment. To survive on limited food resources and to fuel their expensive metabolism during activity, many small mammals employ daily torpor to reduce energy expenditure during the rest phase. We hypothesized that a small terrestrial semelparous marsupial, the brown antechinus Antechinus stuartii, would maximize activity when foraging conditions were favorable to gain fat reserves before their intense breeding period, but would increase torpor use when conditions were poor to conserve these fat reserves. Female antechinus were trapped and implanted with small temperature-sensitive radio transmitters to record body temperature and to quantify torpor expression and activity patterns in the wild. Most antechinus used torpor at least once per day over the entire study period. Total daily torpor use increased and mean daily body temperature decreased significantly with a reduction in minimum ambient temperature. Interestingly, antechinus employed less torpor on days with more rain and decreasing barometric pressure. In contrast to torpor expression, activity was directly related to ambient temperature and inversely related to barometric pressure. Our results reveal that antechinus use a flexible combination of physiology and behavior that can be adjusted to manage their energy budget according to weather variables.
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Affiliation(s)
- Taylor Hume
- 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
| | - Shannon E Currie
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, 2351, Australia.,Leibniz Institute for Zoo and Wildlife Research, Alfred-Kowalke-Str. 17, Berlin, 10315, Germany
| | - Gerhard Körtner
- 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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Turbill C, Stojanovski L. Torpor reduces predation risk by compensating for the energetic cost of antipredator foraging behaviours. Proc Biol Sci 2018; 285:20182370. [PMID: 30963890 PMCID: PMC6304060 DOI: 10.1098/rspb.2018.2370] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Accepted: 11/27/2018] [Indexed: 11/12/2022] Open
Abstract
Foraging activity is needed for energy intake but increases the risk of predation, and antipredator behavioural responses, such as reduced activity, generally reduce energy intake. Hence, the mortality and indirect effects of predation risk are dependent on the energy requirements of prey. Torpor, a controlled reduction in resting metabolism and body temperature, is a common energy-saving mechanism of small mammals that enhances their resistance to starvation. Here we test the hypothesis that torpor could also reduce predation risk by compensating for the energetic cost of antipredator behaviours. We measured the foraging behaviour and body temperature of house mice in response to manipulation of perceived predation risk by adjusting levels of ground cover and starvation risk by 24 h food withdrawal every third day. We found that a voluntary reduction in daily food intake in response to lower cover (high predation risk) was matched by the extent of a daily reduction in body temperature. Our study provides the first experimental evidence of a close link between energy-saving torpor responses to starvation risk and behavioural responses to perceived predation risk. By reducing the risk of starvation, torpor can facilitate stronger antipredator behaviours. These results highlight the interplay between the capacity for reducing metabolic energy expenditure, optimal decisions about foraging behaviour and the life-history ecology of prey.
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Affiliation(s)
- Christopher Turbill
- Hawkesbury Institute for the Environment, Western Sydney University, Richmond, New South Wales, Australia
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Geiser F, Stawski C, Doty AC, Cooper CE, Nowack J. A burning question: what are the risks and benefits of mammalian torpor during and after fires? CONSERVATION PHYSIOLOGY 2018; 6:coy057. [PMID: 30323932 PMCID: PMC6181253 DOI: 10.1093/conphys/coy057] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 08/11/2018] [Accepted: 10/08/2018] [Indexed: 06/08/2023]
Abstract
Although wildfires are increasing globally, available information on how mammals respond behaviourally and physiologically to fires is scant. Despite a large number of ecological studies, often examining animal diversity and abundance before and after fires, the reasons as to why some species perform better than others remain obscure. We examine how especially small mammals, which generally have high rates of energy expenditure and food requirements, deal with fires and post-fire conditions. We evaluate whether mammalian torpor, characterised by substantial reductions in body temperature, metabolic rate and water loss, plays a functional role in survival of mammals impacted by fires. Importantly, torpor permits small mammals to reduce their activity and foraging, and to survive on limited food. Torpid small mammals (marsupials and bats) can respond to smoke and arouse from torpor, which provides them with the possibility to evade direct exposure to fire, although their response is often slowed when ambient temperature is low. Post-fire conditions increase expression of torpor with a concomitant decrease in activity for free-ranging echidnas and small forest-dwelling marsupials, in response to reduced cover and reduced availability of terrestrial insects. Presence of charcoal and ash increases torpor use by captive small marsupials beyond food restriction alone, likely in anticipation of detrimental post-fire conditions. Interestingly, although volant bats use torpor on every day after fires, they respond by decreasing torpor duration, and increasing activity, perhaps because of the decrease in clutter and increase in foraging opportunities due to an increase in aerial insects. Our summary shows that torpor is an important tool for post-fire survival and, although the physiological and behavioural responses of small mammals to fire are complex, they seem to reflect energetic requirements and mode of foraging. We make recommendations on the conditions during management burns that are least likely to impact heterothermic mammals.
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Affiliation(s)
- Fritz Geiser
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
| | - Clare Stawski
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
- Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway
| | - Anna C Doty
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
- Department of Biological Sciences, Arkansas State University, Jonesboro, AR, USA
| | - Christine E Cooper
- School of Molecular and Life Sciences, Curtin University, Perth, Western Australia
| | - Julia Nowack
- Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, Australia
- School of Natural Sciences and Psychology, Liverpool John Moores University, Byrom Street, Liverpool, UK
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Nowack J, Stawski C, Körtner G, Geiser F. Physiological and behavioral responses of an arboreal mammal to smoke and charcoal-ash substrate. Physiol Behav 2018; 184:116-121. [DOI: 10.1016/j.physbeh.2017.11.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 11/08/2017] [Accepted: 11/16/2017] [Indexed: 10/18/2022]
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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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More functions of torpor and their roles in a changing world. J Comp Physiol B 2017; 187:889-897. [PMID: 28432393 PMCID: PMC5486538 DOI: 10.1007/s00360-017-1100-y] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 11/26/2016] [Accepted: 02/26/2017] [Indexed: 02/06/2023]
Abstract
Increased winter survival by reducing energy expenditure in adult animals is often viewed as the primary function of torpor. However, torpor has many other functions that ultimately increase the survival of heterothermic mammals and birds. In this review, we summarize new findings revealing that animals use torpor to cope with the conditions during and after natural disasters, including fires, storms, and heat waves. Furthermore, we suggest that torpor, which also prolongs longevity and was likely crucial for survival of mammals during the time of the dinosaur extinctions, will be advantageous in a changing world. Climate change is assumed to lead to an increase in the occurrence and intensity of climatic disasters, such as those listed above and also abnormal floods, droughts, and extreme temperatures. The opportunistic use of torpor, found in many heterothermic species, will likely enhance survival of these challenges, because these species can reduce energy and foraging requirements. However, many strictly seasonal hibernators will likely face the negative consequences of the predicted increase in temperature, such as range contraction. Overall, available data suggest that opportunistic heterotherms with their flexible energy requirements have an adaptive advantage over homeotherms in response to unpredictable conditions.
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Matthews JK, Stawski C, Körtner G, Parker CA, Geiser F. Torpor and basking after a severe wildfire: mammalian survival strategies in a scorched landscape. J Comp Physiol B 2016; 187:385-393. [DOI: 10.1007/s00360-016-1039-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Revised: 09/14/2016] [Accepted: 09/30/2016] [Indexed: 11/24/2022]
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Nowack J, Delesalle M, Stawski C, Geiser F. Can hibernators sense and evade fires? Olfactory acuity and locomotor performance during deep torpor. Naturwissenschaften 2016; 103:73. [DOI: 10.1007/s00114-016-1396-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 07/27/2016] [Accepted: 07/29/2016] [Indexed: 10/21/2022]
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Post-wildfire physiological ecology of an Australian microbat. J Comp Physiol B 2016; 186:937-46. [PMID: 27245066 DOI: 10.1007/s00360-016-1003-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/05/2016] [Accepted: 05/17/2016] [Indexed: 10/21/2022]
Abstract
Historical patterns of wildfires are being altered as a result of changing climate and therefore are becoming an increasingly pressing global issue. How small mammals deal physiologically with changes in landscape and food availability due to fire remains largely unknown, although recent studies on small heterothermic terrestrial mammals have shown an increase in post-fire torpor use to reduce energy and foraging requirements. However, data on the behavioural and physiological responses of bats after fires are scarce, although potentially these volant species may differ from terrestrial mammals. Therefore, we investigated the post-fire thermal biology and activity of lesser long-eared bats (Nyctophilus geoffroyi) using temperature-telemetry in Warrumbungle National Park, NSW, which experienced a devastating wildfire in 2013. The study comprised two field seasons, one in 2013 within 4 months after the fire, and one in 2015 two years after the fire to identify potential changes in behaviour and physiology. Interestingly, soon after the fire, bats showed significantly shorter torpor bout duration (11.8 ± 12.5 h) and longer normothermia duration (8.7 ± 4.6 h) in comparison to those in 2015 (torpor bout duration: 24.1 ± 23.5 h; normothermia duration: 2.5 ± 1.5 h). Insect availability was significantly (20-fold) higher in 2013 than in 2015, which was likely an important factor resulting in the short average torpor bout duration by N. geoffroyi after the fire. Our data indicate that volant bats appear to show the opposite post-fire behavioural and physiological responses to small terrestrial mammals, showing longer normothermic and active periods and shorter torpor bouts to capitalise on an increase in available post-fire resources.
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Phenotypic plasticity of post-fire activity and thermal biology of a free-ranging small mammal. Physiol Behav 2016; 159:104-11. [PMID: 27001165 DOI: 10.1016/j.physbeh.2016.03.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 03/06/2016] [Accepted: 03/10/2016] [Indexed: 11/20/2022]
Abstract
Ecosystems can change rapidly and sometimes irreversibly due to a number of anthropogenic and natural factors, such as deforestation and fire. How individual animals exposed to such changes respond behaviourally and physiologically is poorly understood. We quantified the phenotypic plasticity of activity patterns and torpor use - a highly efficient energy conservation mechanism - in brown antechinus (Antechinus stuartii), a small Australian marsupial mammal. We compared groups in densely vegetated forest areas (pre-fire and control) with a group in a burned, open habitat (post-fire). Activity and torpor patterns differed among groups and sexes. Females in the post-fire group spent significantly less time active than the other groups, both during the day and night. However, in males only daytime activity declined in the post-fire group, although overall activity was also reduced on cold days in males for all groups. The reduction in total or diurnal activity in the post-fire group was made energetically possible by a ~3.4-fold and ~2.2-fold increase in the proportion of time females and males, respectively, used torpor in comparison to that in the pre-fire and control groups. Overall, likely due to reproductive needs, torpor was more pronounced in females than in males, but low ambient temperatures increased torpor bout duration in both sexes. Importantly, for both male and female antechinus and likely other small mammals, predator avoidance and energy conservation - achieved by reduced activity and increased torpor use - appear to be vital for post-fire survival where ground cover and refuges have been obliterated.
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Verde Arregoitia LD. Biases, gaps, and opportunities in mammalian extinction risk research. Mamm Rev 2015. [DOI: 10.1111/mam.12049] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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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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