HumphriesThomasKramer2001

Référence

Humphries, M.M., Thomas, D.W. and Kramer, D.L. (2001) Torpor and digestion in food-storing hibernators. Physiological and Biochemical Zoology, 74(2):283-292.

Résumé

Many species of hibernating mammals rely on hoarded food rather than body fat to support winter energy requirements. Here, we evaluate whether the associated ingestive and digestive requirements reduce the benefits that food-storing hibernators can accrue from torpor. Using a simple model, we predict (1) that digestive efficiency could either increase or decrease with increased use of torpor, depending on the Q10 of digestion relative to the Q10 of whole-animal metabolism and (2) that increased torpor will result in a linear decrease in energy consumption but an exponential increase in euthermic intake requirements. In 16 captive eastern chipmunks (Tamias striatus), the proportion of time that different individuals spent in torpor was highly variable (29.8% ± 5.9%; 0.0%-86.3%), positively correlated with dry matter digestibility (r2 = 0.53, P = 0.02) and negatively correlated with energy consumption (r2 = 0.72, P = 0.002). Thus, by both increasing conversion efficiency and reducing energy requirements, torpor appears to provide a double benefit for energy conservation by food-storing hibernators. Despite this, a comparative analysis shows that the euthermic intervals of food-storing rodents are four times as long and torpor intervals are half as long as that of fat-storing rodents. Given that required euthermic intake rates are expected to increase exponentially at high levels of torpor, the reduced torpor expression of food-storing species may result from constraints on their ability to load enough food into the gut when euthermic to cover the energy requirements of the subsequent torpor cycle.

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@ARTICLE { HumphriesThomasKramer2001,
    AUTHOR = { Humphries, M.M. and Thomas, D.W. and Kramer, D.L. },
    TITLE = { Torpor and digestion in food-storing hibernators },
    JOURNAL = { Physiological and Biochemical Zoology },
    YEAR = { 2001 },
    VOLUME = { 74 },
    PAGES = { 283-292 },
    NUMBER = { 2 },
    NOTE = { 15222152 (ISSN) Cited By (since 1996): 7 Export Date: 26 April 2007 Source: Scopus CODEN: PBZOF doi: 10.1086/319659 Language of Original Document: English Correspondence Address: Humphries, M.M.; Department of Biology; McGill University Montre?al, Que. H3A 1B1, Canada; email: murrayh@biol.lan.mcgill.ca References: Audet, D., Thomas, D.W., Evaluation of the accuracy of body temperature measurement using external radio transmitters (1996) Can J Zool, 74, pp. 1778-1781; Barclay, R.M.R., Kalcounis, M., Crampton, L.H., Stefan, C., Vonnhof, M.J., Wilkinson, L., Brigham, R.M., Can external radio-transmitters be used to assess body temperature and use of torpor in bats? 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    ABSTRACT = { Many species of hibernating mammals rely on hoarded food rather than body fat to support winter energy requirements. Here, we evaluate whether the associated ingestive and digestive requirements reduce the benefits that food-storing hibernators can accrue from torpor. Using a simple model, we predict (1) that digestive efficiency could either increase or decrease with increased use of torpor, depending on the Q10 of digestion relative to the Q10 of whole-animal metabolism and (2) that increased torpor will result in a linear decrease in energy consumption but an exponential increase in euthermic intake requirements. In 16 captive eastern chipmunks (Tamias striatus), the proportion of time that different individuals spent in torpor was highly variable (29.8% ± 5.9%; 0.0%-86.3%), positively correlated with dry matter digestibility (r2 = 0.53, P = 0.02) and negatively correlated with energy consumption (r2 = 0.72, P = 0.002). Thus, by both increasing conversion efficiency and reducing energy requirements, torpor appears to provide a double benefit for energy conservation by food-storing hibernators. Despite this, a comparative analysis shows that the euthermic intervals of food-storing rodents are four times as long and torpor intervals are half as long as that of fat-storing rodents. Given that required euthermic intake rates are expected to increase exponentially at high levels of torpor, the reduced torpor expression of food-storing species may result from constraints on their ability to load enough food into the gut when euthermic to cover the energy requirements of the subsequent torpor cycle. },
    KEYWORDS = { caching digestion metabolism torpor Tamias striatus },
    OWNER = { brugerolles },
    TIMESTAMP = { 2007.12.05 },
}

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