Seasonal effects on thermoregulatory abilities of the Wahlberg's epauletted fruit bat (Epomophorus wahlbergi) in KwaZulu-Natal, South Africa

Downs, Colleen T.; Zungu, Manqoba M.; Brown, Mark

doi:10.1016/j.jtherbio.2011.12.003

Cited by 21 publications

(29 citation statements)

References 85 publications

(108 reference statements)

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“…The lack of seasonal changes in the M b of E. wahlbergi in this study contrasts with the significantly higher M b (by ~15%) in winter reported for a captive population of the same species (Downs et al, 2012). The latter population originated from a site near the east coast of South Africa that is more mesic than our study area.…”

Section: Discussioncontrasting

confidence: 98%

“…In northtemperate climates, winter acclimatisation in birds typically involves the upregulation of both M sum and BMR (reviewed by McKechnie and Swanson, 2010;Swanson, 2010), whereas in subtropical habitats avian BMR is generally lower in winter than in summer (Smit and McKechnie, 2010). Among mammals, winter decreases in body mass are generally associated with proportional reductions in BMR in species smaller than 100 g, whereas intermediate-sized (0.1-10 kg) species typically show winter increases in BMR (Lovegrove, 2005 (Almeida and Cruz-Neto, 2011;Coburn and Geiser, 1998) or increase in winter (Downs et al, 2012). Seasonal acclimatisation in mammalian M sum has received far less attention; Lovegrove (Lovegrove, 2005) found limited evidence for winter increases in non-shivering thermogenesis (NST) capacity among small mammals, and most other studies have similarly focused on NST rather than M sum (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Many endotherms respond to seasonal variation in energy requirements and/or food availability by means of acclimatisation involving changes in both M sum and/or BMR, with the direction and magnitude of these changes varying widely among and within species (Lovegrove, 2005;Swanson, 2010). In northtemperate climates, winter acclimatisation in birds typically involves the upregulation of both M sum and BMR (reviewed by McKechnie and Swanson, 2010;Swanson, 2010), whereas in subtropical habitats avian BMR is generally lower in winter than in summer (Smit and McKechnie, 2010 (Almeida and Cruz-Neto, 2011;Coburn and Geiser, 1998) or increase in winter (Downs et al, 2012). Seasonal acclimatisation in mammalian M sum has received far less attention; Lovegrove (Lovegrove, 2005) found limited evidence for winter increases in non-shivering thermogenesis (NST) capacity among small mammals, and most other studies have similarly focused on NST rather than M sum (e.g.…”

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Summit metabolism and metabolic expansibility in Wahlberg's epauletted fruit bats (Epomophorus wahlbergi): seasonal acclimatisation and effects of captivity

Minnaar

Bennett

Chimimba

et al. 2013

Journal of Experimental Biology

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Summit metabolism (M sum ), the maximum rate of resting metabolic thermogenesis, has been found to be broadly correlated with climatic variables and the use of heterothermy in some endotherms. Far less is known about M sum and metabolic expansibility [ME, the ratio of M sum to basal metabolic rate (BMR)] in bats compared with many other endotherm taxa. We measured BMR and M sum during winter and summer in captive and wild populations of a pteropodid from the southern subtropics, Wahlberg's epauletted fruit bat (Epomophorus wahlbergi) in Pretoria, South Africa. The M sum of fruit bats ranged from 5.178±0.611 W (captive, summer) to 6.006±0.890 W (captive, winter), and did not vary significantly between seasons. In contrast, BMR decreased by 17-25% in winter. The combination of seasonally stable M sum but flexible BMR resulted in ME being significantly higher in winter than in summer, ranging from 7.24±1.49 (wild, summer) to 13.11±2.14 (captive, winter). The latter value is well above the typical mammalian range. Moreover, both M sum and ME were significantly higher in captive bats than in wild individuals; we speculate this represents a phenotypic response to a reduction in exerciseassociated heat production while in captivity. Our data for E. wahlbergi, combined with those currently available for other chiropterans, reveal that M sum in bats is highly variable compared with allometrically expected values for other mammals.KEY WORDS: Acclimatisation, Cold exposure, Helox, Phenotypic flexibility, Thermogenic capacity INTRODUCTIONThe lowest environmental temperature to which an endotherm can defend normothermic body temperature (T b ) is determined primarily by its maximum capacity for metabolic thermogenesis (Scholander et al., 1950). Summit metabolism (M sum ) is the maximum rate of resting metabolic thermogenesis in the absence of exercise-associated heat production (Swanson et al., 1996) [also referred to as cold-induced peak metabolic rate (Wiersma et al., 2007)]. Among mammals, metabolic expansibility [ME, the ratio of M sum to basal metabolic rate (BMR); also referred to as factorial aerobic scope] is typically 4-8, but may be as high as 10-13 (Careau, 2013;Hinds et al., 1993). Most avian ME values are similar to those typical of mammals, with maximum reported values of 9.0-9. production capacity is correlated with climate, with M sum generally being higher in species inhabiting colder regions (Rezende et al., 2004;Swanson and Garland, 2009).One endotherm order about which remarkably little is known in terms of resting heat production capacity is the Chiroptera. The first published estimate of M sum in a bat of which we are aware was for the molossid Tadarida brasiliensis, in which mass-specific M sum was equivalent to ~21× BMR (Canals et al., 2005). The very high ME value for T. brasiliensis contrasts with more recent data for three frugivorous phyllostomids (Artibeus lituratus, Sturnira lilium and Carollia perspicillata) in which ME ranged from 3.4 to 5.2 (Almeida and Cruz-Neto, 2011).A priori, two...

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Section: Discussioncontrasting

confidence: 98%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Summit metabolism and metabolic expansibility in Wahlberg's epauletted fruit bats (Epomophorus wahlbergi): seasonal acclimatisation and effects of captivity

Minnaar

Bennett

Chimimba

et al. 2013

Journal of Experimental Biology

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“…The rates of TEWL we observed in E. wahlbergi over the T a range of 10Њ-35ЊC are considerably higher than those reported previously for this species by Downs et al (2012). For instance, in our study, mean TEWL at T a ≈ 35ЊC was 7.73 mg g Ϫ1 h…”

Section: Discussioncontrasting

confidence: 79%

Partitioning of Evaporative Water Loss into Respiratory and Cutaneous Pathways in Wahlberg's Epauletted Fruit Bats (Epomophorus wahlbergi)

Minnaar¹,

Bennett²,

Chimimba³

et al. 2014

Physiological and Biochemical Zoology

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The relative contributions of respiratory and cutaneous evaporation to total evaporative water loss (TEWL) and how the partitioning of these two avenues varies with environmental temperature has received little attention in bats. We trained Wahlberg's epauletted fruit bats (Epomophorus wahlbergi) captured in Pretoria, South Africa, to wear latex masks while hanging in respirometry chambers, and we measured respiratory evaporative water loss (REWL) and cutaneous evaporative water loss (CEWL) over air temperatures (T a ) from 10Њ to 40ЊC. The bats' normothermic body temperature (T b ) was approximately 36ЊC, which increased at higher T a to 40.5Њ ‫ע‬ 1.0ЊC at T a ≈ 40ЊC. Both TEWL and resting metabolic rate (RMR) increased sharply at T a 135ЊC, with a mean TEWL at 40ЊC equivalent to 411% of that at 30ЊC. The increase in TEWL was driven by large increases in both CEWL and REWL. CEWL comprised more than 50% of TEWL over the entire T a range, with the exception of T a ≈ 40ЊC, where REWL accounted for 58% of evaporative water loss. Surface area-specific CEWL increased approximately sixfold with increasing T a . Thermoregulation at T a approaching or exceeding T b involved a considerable energetic cost, with RMR at T a ≈ 40ЊC exceeding by 24% that measured at T a ≈ 10ЊC. Our data do not support recent arguments that respiratory gas exchange across the wing membranes represents 5%-10% of the total in E. wahlbergi.

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“…Two populations of Wahlberg's epauletted fruit bats (Epomophorus wahlbergi) from South Africa showed seasonal changes in BMR in opposite directions, with one population decreasing whole-animal BMR by 16-25 % but another increasing it by 40 % (Minnaar et al 2014;Downs et al 2012). …”

Section: Discussionmentioning

confidence: 99%

Global patterns of seasonal acclimatization in avian resting metabolic rates

2015

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The adjustment of resting metabolic rates represents an important component of avian seasonal acclimatization, with recent studies revealing substantial differences between summer and winter in birds from a wide range of latitudes. We compared seasonal variation in basal metabolic rate (BMR) and summit metabolism (Msum) between temperate and tropical/subtropical latitudes, and examined correlations with latitude and temperature. The direction and magnitude of seasonal adjustments in BMR are broadly related to temperature and latitude, but are significantly more variable among tropical and subtropical species compared to those inhabiting temperate zones. Winter adjustments in BMR among subtropical species, when expressed relative to summer 1 values, range from decreases of approximately 35 % to increases of more than 60 %, whereas the majority of temperate-zone species show increases in BMR during winter. Relatively few seasonal Msum data exist for tropical/subtropical species, but those that are available involve responses ranging from winter decreases to increases of similar magnitude to those characteristic of many temperate-zone species. Recent studies also highlight the substantial variation in seasonal adjustments that may occur within species, and reiterate the need for further investigations of the relative roles of environmental variables such as temperature and food availability as determinants of seasonal metabolic variation.

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Seasonal effects on thermoregulatory abilities of the Wahlberg's epauletted fruit bat (Epomophorus wahlbergi) in KwaZulu-Natal, South Africa

Cited by 21 publications

References 85 publications

Summit metabolism and metabolic expansibility in Wahlberg's epauletted fruit bats (Epomophorus wahlbergi): seasonal acclimatisation and effects of captivity

Summit metabolism and metabolic expansibility in Wahlberg's epauletted fruit bats (Epomophorus wahlbergi): seasonal acclimatisation and effects of captivity

Partitioning of Evaporative Water Loss into Respiratory and Cutaneous Pathways in Wahlberg's Epauletted Fruit Bats (Epomophorus wahlbergi)

Global patterns of seasonal acclimatization in avian resting metabolic rates

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