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Boyers M, Parrini F, Owen-Smith N, Erasmus BFN, Hetem RS. Contrasting capabilities of two ungulate species to cope with extremes of aridity. Sci Rep 2021; 11:4216. [PMID: 33603115 PMCID: PMC7893036 DOI: 10.1038/s41598-021-83732-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 02/08/2021] [Indexed: 11/09/2022] Open
Abstract
Southern Africa is expected to experience increased frequency and intensity of droughts through climate change, which will adversely affect mammalian herbivores. Using bio-loggers, we tested the expectation that wildebeest (Connochaetes taurinus), a grazer with high water-dependence, would be more sensitive to drought conditions than the arid-adapted gemsbok (Oryx gazella gazella). The study, conducted in the Kalahari, encompassed two hot-dry seasons with similar ambient temperatures but differing rainfall patterns during the preceding wet season. In the drier year both ungulates selected similar cooler microclimates, but wildebeest travelled larger distances than gemsbok, presumably in search of water. Body temperatures in both species reached lower daily minimums and higher daily maximums in the drier season but daily fluctuations were wider in wildebeest than in gemsbok. Lower daily minimum body temperatures displayed by wildebeest suggest that wildebeest were under greater nutritional stress than gemsbok. Moving large distances when water is scarce may have compromised the energy balance of the water dependent wildebeest, a trade-off likely to be exacerbated with future climate change.
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Affiliation(s)
- Melinda Boyers
- Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, 2050, South Africa. .,Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, 2050, South Africa.
| | - Francesca Parrini
- Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Norman Owen-Smith
- Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Barend F N Erasmus
- Global Change Institute, University of the Witwatersrand, Johannesburg, 2050, South Africa.,Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, 0028, South Africa
| | - Robyn S Hetem
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, 2050, South Africa.,School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, 2050, South Africa
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Maloney SK, Marsh MK, McLeod SR, Fuller A. Heterothermy is associated with reduced fitness in wild rabbits. Biol Lett 2018; 13:rsbl.2017.0521. [PMID: 29212751 DOI: 10.1098/rsbl.2017.0521] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 11/14/2017] [Indexed: 11/12/2022] Open
Abstract
An increase in variation in the 24 h pattern of body temperature (heterothermy) in mammals can be induced by energy and water deficits. Since performance traits such as growth and reproduction also are impacted by energy and water balance, we investigated whether the characteristics of the body temperature rhythm provide an indication of the reproductive success of an individual. We show that the amplitude of the daily rhythm of body temperature in wild rabbits (Oryctolagus cuniculus) prior to breeding is inversely related to the number of pregnancies in the subsequent seven months, while the minimum daily body temperature is positively correlated to the number of pregnancies. Because reproductive output could be predicted from characteristics of the core body temperature rhythm prior to the breeding season, we propose that the pattern of the 24 h body temperature rhythm could provide an index of animal fitness in a given environment.
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Affiliation(s)
- Shane K Maloney
- School of Human Sciences, University of Western Australia, Stirling Highway, Crawley 6009, Australia .,Brain Function Research Group, School of Physiology, University of the Witwatersrand, Medical School, 7 York Road, Parktown 2193, South Africa
| | - Maija K Marsh
- Environment Department, University of York, Heslington, York YO10 5DD, UK
| | - Steven R McLeod
- Vertebrate Pest Research Unit, New South Wales Department of Primary Industries, Forest Road, Orange, New South Wales 2800, Australia
| | - Andrea Fuller
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Medical School, 7 York Road, Parktown 2193, South Africa
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Abstract
The thermoregulatory functions may vary with age. Thermosensitivity is active in neonates and children; both heat production and heat loss effector mechanisms are functional but easily exhaustable. Proportional and lasting defense against thermal challenges is difficult, and both hypothermia and hyperthermia may easily develop. Febrile or hypothermic responses to infections or endotoxin can also develop, together with confusion. In small children febrile convulsions may be dangerous. In old age the resting body temperature may be lower than in young adults. Further, thermosensitivity decreases, the thresholds for activating skin vasomotor and evaporative responses or metabolism are shifted, and responses to thermal challenges are delayed or insufficient: both hypothermia and hyperthermia may develop easily. Infection-induced fevers are often limited or absent, or replaced by hypothermia. Various types of brain damage may induce special forms of hypothermia, hyperthermia, or severe fever. Impaired mental state often accompanies hypothermia and hyperthermia, and may occasionally be a dominant feature of infection (instead of the most commonly observed fever). Aging brings about a turning point in women's life: the menopause. The well-known influence of regular hormonal cycles on the thermoregulation of a woman of fertile age gives way to menopausal hot flushes caused by estrogen withdrawal. Not all details of this thermoregulatory anomaly are fully understood yet.
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Strauss WM, Hetem RS, Mitchell D, Maloney SK, O'Brien HD, Meyer LCR, Fuller A. Body water conservation through selective brain cooling by the carotid rete: a physiological feature for surviving climate change? CONSERVATION PHYSIOLOGY 2017; 5:cow078. [PMID: 29383253 PMCID: PMC5778374 DOI: 10.1093/conphys/cow078] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 12/16/2016] [Accepted: 01/03/2017] [Indexed: 06/07/2023]
Abstract
Some mammals have the ability to lower their hypothalamic temperature below that of carotid arterial blood temperature, a process termed selective brain cooling. Although the requisite anatomical structure that facilitates this physiological process, the carotid rete, is present in members of the Cetartiodactyla, Felidae and Canidae, the carotid rete is particularly well developed in the artiodactyls, e.g. antelopes, cattle, sheep and goats. First described in the domestic cat, the seemingly obvious function initially attributed to selective brain cooling was that of protecting the brain from thermal damage. However, hyperthermia is not a prerequisite for selective brain cooling, and selective brain cooling can be exhibited at all times of the day, even when carotid arterial blood temperature is relatively low. More recently, it has been shown that selective brain cooling functions primarily as a water-conservation mechanism, allowing artiodactyls to save more than half of their daily water requirements. Here, we argue that the evolutionary success of the artiodactyls may, in part, be attributed to the evolution of the carotid rete and the resulting ability to conserve body water during past environmental conditions, and we suggest that this group of mammals may therefore have a selective advantage in the hotter and drier conditions associated with current anthropogenic climate change. A better understanding of how selective brain cooling provides physiological plasticity to mammals in changing environments will improve our ability to predict their responses and to implement appropriate conservation measures.
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Affiliation(s)
- W. Maartin Strauss
- Brain Function Research Group, School of Physiology, Faculty of Heath Sciences, University of the Witwatersrand, Johannesburg, 2193, South Africa
- Department of Environmental Science, University of South Africa, Johannesburg, 1709, South Africa
| | - Robyn S. Hetem
- Brain Function Research Group, School of Physiology, Faculty of Heath Sciences, University of the Witwatersrand, Johannesburg, 2193, South Africa
- School of Animal, Plant and Environmental Sciences, Faculty of Science, University of the Witwatersrand, Johannesburg, 2050, South Africa
| | - Duncan Mitchell
- Brain Function Research Group, School of Physiology, Faculty of Heath Sciences, University of the Witwatersrand, Johannesburg, 2193, South Africa
- School of Anatomy, Physiology, and Human Biology, University of Western Australia, Perth, WA 6009, Australia
| | - Shane K. Maloney
- Brain Function Research Group, School of Physiology, Faculty of Heath Sciences, University of the Witwatersrand, Johannesburg, 2193, South Africa
- School of Anatomy, Physiology, and Human Biology, University of Western Australia, Perth, WA 6009, Australia
| | - Haley D. O'Brien
- Department of Anatomy and Cell Biology, Oklahoma State University Center for Health Sciences, Oklahoma, OK 74107, USA
| | - Leith C. R. Meyer
- Brain Function Research Group, School of Physiology, Faculty of Heath Sciences, University of the Witwatersrand, Johannesburg, 2193, South Africa
- Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Pretoria, 0110, South Africa
| | - Andrea Fuller
- Brain Function Research Group, School of Physiology, Faculty of Heath Sciences, University of the Witwatersrand, Johannesburg, 2193, South Africa
- Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Pretoria, 0110, South Africa
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