Thermoregulatory differences in African mole-rat species from disparate habitats: Responses and limitations

McGowan, Natasha E.; Scantlebury, David; Bennett, Nigel C.; Maule, Aaron G.; Marks, Nikki J.

doi:10.1016/j.jtherbio.2019.102495

Cited by 14 publications

(13 citation statements)

References 48 publications

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“…However, increased soil moisture during summer may provide a cooling effect via conduction to decrease body temperature during or after activity bouts by pressing their ventral surface against a cooler surface (Okrouhlík et al, 2015;Vejmělka et al, 2021). Seasonal changes in daily activity would be an effective thermoregulatory adaptation to reduce the risk of overheating while digging (Goldman et al, 1997;McGowan et al, 2020). Locomotor activity was concentrated during periods of lower temperatures in laboratory studies (van Jaarsveld et al, 2019;Hart et al, 2021) and in periods of moderate temperature in wild studies (this study, Šklíba et al, 2014, 2016b).…”

Section: Discussionmentioning

confidence: 99%

Seasonal Changes in Locomotor Activity Patterns of Wild Social Natal Mole-Rats (Cryptomys hottentotus natalensis)

et al. 2022

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Differences in individual locomotor activity patterns may be linked to a number of ecological factors, such as changes in ambient temperature or photoperiod. Observations on subterranean mammals suggest that they exhibit diel rhythms despite the lack of visual cues in their underground burrows, but it is unknown how seasonality and individual characteristics affect their activity. In this study we use RFID technology to monitor daily activity patterns of wild, social Natal mole-rats (Cryptomys hottentotus natalensis) during the summer and winter to investigate how their activity varies with season and whether their activity depends on individual characteristics such as body mass, sex and reproductive status. We found that in winter, individuals were more active during the time with the highest soil temperatures, whereas in summer, they showed a bimodal activity pattern during early morning and late afternoon coinciding with cooler soil temperatures. Individual characteristics, including reproductive status, did not affect general activity indicating that reproductive and non-reproductive individuals contribute equally to cooperative behaviors. We suggest that the activity patterns may be a behavioral adaptation to avoid extreme burrow temperatures and a mechanism to maintain a stable core body temperature. We highlight the advantages of RFID technology to study wild small mammal movements.

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Section: Discussionmentioning

confidence: 99%

Seasonal Changes in Locomotor Activity Patterns of Wild Social Natal Mole-Rats (Cryptomys hottentotus natalensis)

et al. 2022

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“…The remaining colony members are reproductively suppressed, and a marked division of labor, with breeders spending approximately half as much time foraging as their non-breeding counterparts, is apparent (Scantlebury et al, 2006c;Lacey and Sherman, 2009;Oosthuizen and Bennett, 2015;Francioli et al, 2020;Houslay et al, 2020). Furthermore, they persist over a wide range of climates, elevations and substrates from both mesic and arid environments, with behavioral and physiological adaptations being suggested to correspond to the macroclimate they experience (Bennett et al, 1988;Faulkes et al, 2004;McGowan et al, 2020;Wallace et al, 2021). For example, species of African mole-rats that inhabit soft sandy substrates with a mesic climate are often solitary, possess a larger body masses and use both their teeth and forelimbs, "scratch digging", to dig, such as those species belonging to the genus of Bathyergus (Bennett and Faulkes, 2000).…”

Section: Introductionmentioning

confidence: 99%

“…The added energy expenditure necessary for digging, in conjunction with the fact that African mole-rats obtain all their nutrient and water requirements from the storage organs of underground geophytes (Bennett et al, 1994;Bennett and Jarvis, 1995;Spinks et al, 1999;Malherbe et al, 2003), has been suggested to exacerbate the selection pressures placed upon African mole-rats to enable them to locate adequate resources for survival and reproduction (Bennett and Faulkes, 2000). The energetic cost of digging under the unique microclimate within the tunnels they inhabit has been hypothesized to lead to lower RMRs and body temperatures displayed by African mole-rats in comparison to aboveground rodent species (McNab, 1966;Shkolnik and Schmidt-Nielsen, 1976;Bennett et al, 1992McGowan et al, 2020) and a social and eusocial lifestyle in species inhabiting very arid environments [the ' Arid-Food-Distribution-Hypothesis ; Lacey and Sherman (1997)].…”

Section: Introductionmentioning

confidence: 99%

Energetics and Water Flux in the Subterranean Rodent Family Bathyergidae

et al. 2022

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The doubly labeled water (DLW) technique and indirect calorimetry enable measurement of an animal’s daily energy expenditure (DEE, kJ/day), resting metabolic rate (RMR, kJ/d), sustained metabolic scope (SusMS), body fat content (BF, %) as well as water turnover (WTO, ml/day), and water economy index (ml/kJ). Small mammals have been the primary focus of many of the DLW studies to date. From large multi-species analyses of the energetics and water flux of aboveground small mammals, well-defined trends have been observed. These trends mainly refer to an adaptive advantage for lower RMR, DEE, SusMS, WTO and WEI in more ariddwelling animals to increase water and energy savings under low and unpredictable resource availability. The study of the subterranean rodent family Bathyergidae (African mole-rats) has been of particular interest with regards to field metabolic rate and metabolic studies. Although a great deal of research has been conducted on the Bathyergidae, a complete overview and multi-species analysis of the energetics and water flux of this family is lacking. Consequently, we assessed DEE, RMR, SusMS, BF, WTO and WEI across several different species of bathyergids from various climatic regions, and compared these to the established patterns of energetics and water flux for aboveground rodents. There was notable variation across the Bathyergidae inhabiting areas with different aridities, often contrary to the variations observed in above-ground species. These include increased DEE and WEI in arid-dwelling bathyergid species. While the climate was not a clear factor when predicting the SusMS of a bathyergid species, rather the degree of group living was a strong driver of SusMS, with solitary species possessing the highest SusMS compared to the socially living species. We conclude that the constraints of the underground lifestyle and the consequent spectrum of social behaviors possessed by the family Bathyergidae are most likely to be more crucial to their energetics and water flux than their habitat; however other important unstudied factors may still be at play. More so, this study provides evidence that often unreported parameters, measured through use of the DLW technique (such as BF and WEI) can enable species to be identified that might be at particular risk to climate change.

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“…Although no NST estimation was performed, Boyles et al ., (2012) proposed that the longer and denser fur of C. h. pretoriae might be more important for thermoregulation of this species living in the colder environment than that of the Mashona mole‐rat Fukomys darlingi living in a warmer climate. Furthermore, McGowan et al ., (2020) evaluated T b and T s of different social bathyergids and suggested that species living in colder environments prioritize increasing heat generation and insulating against heat loss, such as is the case of Natal mole‐rat C. h. natalensis . Thus, bathyergid species living in cold conditions might show a tendency to follow an energy conservation strategy, taking advantage of the insulative fur (i.e., low C wet ) rather than increasing heat production.…”

Section: Discussionmentioning

confidence: 99%

Non‐shivering thermogenesis in four species of African mole‐rats differing in their sociality

et al. 2021

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Many mammalian species are adapted to living in burrows for most of their lives. Inhabiting such thermally stable environments may influence the variation on the species thermogenic capacity, particularly non‐shivering thermogenesis (NST). African mole‐rats (Bathyergidae) are subterranean rodents occurring in fynbos, grassland and wooded savannas across sub‐Saharan Africa that vary in the complexity of their social systems, ranging from strictly solitary to highly social species. The presence and magnitude of NST are well known in social bathyergids, but no such data exist for their solitary counterparts. In this study, we quantified NST in three solitary mole‐rat species represented by three distinct genera together with one social species. Our results showed that NST in all species is functional. Maximum metabolic rate after norepinephrine injection was equivalent to 269% of resting values in the social giant mole‐rat Fukomys mechowii and 166%, 282% and 157% in the three solitary species: the silvery mole‐rat Heliophobius argenteocinereus, the Cape mole‐rat Georychus capensis and the Cape dune mole‐rat Bathyergus suillus, respectively. To test our prediction that NST capacity is higher in solitary bathyergids, we combined our data with those available for other members of this family. In contrast to our prediction, NST did not differ between social and solitary bathyergids. Body mass, as the main factor, and minimum air temperature (Tmin), accounts for more than 80% of NST variation in bathyergid mole‐rats.

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Thermoregulatory differences in African mole-rat species from disparate habitats: Responses and limitations

Cited by 14 publications

References 48 publications

Seasonal Changes in Locomotor Activity Patterns of Wild Social Natal Mole-Rats (Cryptomys hottentotus natalensis)

Seasonal Changes in Locomotor Activity Patterns of Wild Social Natal Mole-Rats (Cryptomys hottentotus natalensis)

Energetics and Water Flux in the Subterranean Rodent Family Bathyergidae

Non‐shivering thermogenesis in four species of African mole‐rats differing in their sociality

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