Seasonal Body Temperature Fluctuations and Energetic Strategies in Free-Ranging Eastern Woodchucks (Marmota Monax)

Zervanos, Stam M.; Salsbury, Carmen M.

doi:10.1644/1545-1542(2003)084<0299:sbtfae>2.0.co;2

Cited by 32 publications

(17 citation statements)

References 33 publications

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“…Any change in T set will lead to a corresponding change in the lower and upper threshold of thermoregulatory responses. It is well known that T set , BMR, and body core temperature (T c ) can fluctuate on a circadian and circannual basis (3,27,36,74). Therefore, it is most likely that prolonged peripheral cooling in red deer associated with a reduction of heart rate is the result of an expansion of the amplitude of the circadian T set rhythm.…”

Section: Annual Changes Of Mrs and Underlying Causessupporting

confidence: 56%

Nocturnal hypometabolism as an overwintering strategy of red deer (Cervus elaphus)

Arnold

Ruf

Reimoser

et al. 2004

American Journal of Physiology-Regulatory, Integrative and Comp

126

143

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. Nocturnal hypometabolism as an overwintering strategy of red deer (Cervus elaphus). Am J Physiol Regul Integr Comp Physiol 286: R174-R181, 2004. First published September 11, 2003 10.1152/ajpregu.00593.2002Herbivores of temperate and arctic zones are confronted during winter with harsh climatic conditions and nutritional shortness. It is still not fully understood how large ungulates cope with this twofold challenge. We found that red deer, similar to many other northern ungulates, show large seasonal fluctuations of metabolic rate, as indicated by heart rate, with a 60% reduction at the winter nadir compared with the summer peak. A previously unknown mechanism of energy conservation, i.e., nocturnal hypometabolism associated with peripheral cooling, contributed significantly to lower energy expenditure during winter. Predominantly during late winter night and early morning hours, subcutaneous temperature could decrease substantially. Importantly, during these episodes of peripheral cooling, heart rate was not maintained at a constant level, as to be expected from classical models of thermoregulation in the thermoneutral zone, but continuously decreased with subcutaneous temperature, both during locomotor activity and at rest. This indicates that the circadian minimum of basal metabolic rate and of the set-point of body temperature regulation varied and dropped to particularly low levels during late winter. Our results suggest, together with accumulating evidence from other species, that reducing endogenous heat production is not restricted to hibernators and daily heterotherms but is a common and well-regulated physiological response of endothermic organisms to energetically challenging situations. Whether the temperature of all tissues is affected, or the body shell only, may simply be a result of the duration and degree of hypometabolism and its interaction with body size-dependent heat loss. hypometabolism; hypothermia; winter adaptation; body temperature regulation MANY UNGULATES ARE CAPABLE of withstanding long and cold winters with low food availability. Large body size, excellent fur insulation, and countercurrent heat exchange mechanisms contribute to minimize energy requirements under cold load. However, reduced heat loss alone can hardly explain the substantially lowered metabolic rate (MR) of northern ungulates and the apparently ubiquitous decrease of voluntary food intake during winter (4,13,18,28,35,37,42,44,59,63,72). The search for mechanism to explain reduced energy expenditure during winter has so far produced equivocal results. Studies on white-tailed deer [Odocoileus virginianus (66)], moose [Alces alces (56, 57)], roe deer [Capreolus capreolus (69)], and wapiti [Cervus elaphus nelsoni (49)] reported that animals had reduced MRs during winter. However, other studies failed to find any differences between summer and winter basal metabolic rate (BMR) and concluded that seasonal variations in MR were merely consequences of different activity levels and failures to measure animals within thei...

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Section: Annual Changes Of Mrs and Underlying Causessupporting

confidence: 56%

Nocturnal hypometabolism as an overwintering strategy of red deer (Cervus elaphus)

Arnold

Ruf

Reimoser

et al. 2004

American Journal of Physiology-Regulatory, Integrative and Comp

126

143

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“…By Jun., adult males began to gain mass and weighed more than females, as seen in other woodchuck populations (Hamilton 1934; Snyder et al. 1961; Zervanos & Salsbury 2003). Nearly all females over 2 yr old bred in this population, and energetic demands of reproduction could explain the delay in weight gain until later in summer (Armitage et al.…”

Section: Discussionmentioning

confidence: 66%

Social Organization in Woodchucks (Marmota monax) and its Relationship to Growing Season

Maher

2006

Ethology

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Among sciurids, delayed dispersal may result from slow rates of maturation associated with short growing seasons and large body mass. However, woodchucks (Marmota monax) experience a range of ecological conditions and display behavioral flexibility, often ignored in models of sociality. To investigate relationships between social organization and growing season, I collected data on interaction rates, timing of dispersal, and body mass of woodchucks in southern Maine, and I gathered comparative data from the literature. Interaction rates peaked in spring then declined, with agonistic interactions exceeding amicable interactions in adults and in yearling males. Adult males and females weighed comparable amounts early and late in the season, but female weights lagged behind those of males in early summer. Woodchucks did not attain adult mass until after their second hibernation period. Nearly 50% of juveniles postponed dispersal beyond their first summer, and nearly half of those individuals remained philopatric in the following year. Populations faced with longer growing seasons matured more slowly, but timing of dispersal did not correspond to growing season or maturation rate. Other ecological factors, including burrow density, or benefits associated with joint hibernation, may influence timing of dispersal and degree of sociality and deserve further study.

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“…broweri appears to have a strategy for entering torpor that differs from the uninterrupted pattern of decrease in body temperature typical of S. parryii (KARPOVICH et al 2009), M. marmota (ARNOLD 1988, ORTMANN & HELDMAIER 2000, M. monax (ZERVANOS & SALSBURY 2003), and M. aviventris (WOODS et al 2002). In M. broweri, T b drops rapidly (-5.87 °C/hr) from euthermic body temperatures during arousal to an average of 21.5 °C, at which point cooling slows dramatically to an ambient temperature-related rate less than -0.43 °C/hr after a small 1.2 °C temperature increase (Fig.…”

Section: Discussionmentioning

confidence: 86%

Body temperature patterns during hibernation in a free-living Alaska marmot (Marmota broweri)

Lee

Barnes

Buck

2009

Ethology Ecology & Evolution

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Seasonal Body Temperature Fluctuations and Energetic Strategies in Free-Ranging Eastern Woodchucks (Marmota Monax)

Cited by 32 publications

References 33 publications

Nocturnal hypometabolism as an overwintering strategy of red deer (Cervus elaphus)

Nocturnal hypometabolism as an overwintering strategy of red deer (Cervus elaphus)

Social Organization in Woodchucks (Marmota monax) and its Relationship to Growing Season

Body temperature patterns during hibernation in a free-living Alaska marmot (Marmota broweri)

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