Previous studies of the pouched mouse (Saccostomus campestris) have revealed that during reproduction there is no increase in food consumption, although resting energy demands, measured by respirometry, increase substantially. One explanation for this anomalous situation is that these mice may routinely use torpor to compensate their energy budgets.
We measured the daily energy expenditure of eleven individual pouched mice over three consecutive days using the doubly-labelled water technique. The mice were housed in cages where they had free access to food and water, at an average temperature of 26.5 °C, and exposed to a natural photoperiod (February Pretoria).
There was a large day-to-day variation in energy expenditure within each individual. The coefficient of variation in daily energy demand averaged 24.5%. By comparing the correlation of estimates for consecutive and nonconsecutive days we established that this variation was not a consequence of errors in the isotopic technique.
The scaling exponent of the measures of energy expenditure to mass was 1.196 (sd = 0.37: not significantly different to 1.0). We corrected all the estimates to a mean mass of 61.3 g using a scaling exponent of 1.0. We then compared the daily energy demands with expected energy requirements for endothermic animals at rest in respirometers. All the estimates of daily energy expenditure exceeded those anticipated from the resting costs, and averaged about 2.1× greater. We found no compelling evidence therefore that Saccostomus campestris routinely utilizes long (>8 hours) bouts of torpor to compensate its energy budget.
Purchase
Buy instant access (PDF download and unlimited online access):
Institutional Login
Log in with Open Athens, Shibboleth, or your institutional credentials
Personal login
Log in with your brill.com account
Drent R., Daan S.The prudent parent: energetic adjustments in avian breeding. Ardea: 1980 272 285
Ellison G.T.H., Skinner J.D.The influence of ambient temperature on the spontaneous daily torpor in three karyotypic variants of pouched mice “Saccostomus campestris from Southern Africa. Journal of Thermal Biology 1990
Glazier D.S.Energetics of litter size of five species of Peromyscus with generalisation for other mammals Journal of Mammalogy 1985 66 629 642
Haim A., Ellison G.T.H., Skinner J.D.Saccostomus campestris 1988 123 127Thermoregulatory circadian rhythms in the pouched mouse Comparative Biochemistry and Physiology 91A
Haim A., Racey P.A., Speakman J.R., Ellison G.T.H., Skinner J.D.Seasonal acclimatization and thermoregulation in the pouched mouse (Saccostomus campestris) Journal of Thermal Biology 1991 16 13 17
Innes D.G.L., Millar J.S.Body weight, litter size and energetics of reproduction in Clethrionomys gapperi Microtuspennslyvanicus Canadian Journal of Zoology 1981 59 785 789
Kingdon J.East African Mammals An atlas of evolution in Africa Volume IIb Academic Press London 1974
Lifson N., McClintock R.M.Theory of use of the turnover rates of body water for measuring energy and material balance Journal of Theoretical Biology 1966 12 46 74
Nagy K.A.1980CO2 production in animals: analysis of potential errors in the doubly-labelled water method. American Journal of Physiology 238 R466-R473
Neal B.R.Seasonal feeding habits of small mammals in Kenya Z. Saugetierkd 1984 49 4 226 234
Nicoll M.E., Thompson S.D.Basal metabolic rate and the energetics of reproduction in therian mammals. Nature 321 1987 690 693
Packard G.C., Boardman T.J., The misuse of ratios to scale physiological data that vary allometrically with body size. New directions in ecological physiology Feder M.E., Bennett A.F., Burggren W.W., Huey R.B.Cambridge University Press Cambridge 1987 216 240
Peterson C.C., Nagy K.A., Diamond J.Sustained metabolic scope Proceedings of the National Academy of Science 1990 87 2324 2328
Perrin M.R., Clarke J.R.A preliminary investigation of the bioenergetics of pregnancy and lactation of Praomys natalensis Saccostomus campestris South African Journal of Zoology 1987 22 2 77 82
Racey P.A., Speakman J.R.The energy costs of pregnancy and lactation in hetero thermic bats Symposia of the Zoological Society of London 1987 57 107 125
Shortridge C.C.The mammals of S.W. Africa. Volume I. Heinemann London 1971
Skinner J.D., Smithers R.H.N.The mammals of the Southern African sub region University of Pretoria Pretoria 1990
Smithers R.H.N., Wilson V.J.Check list and atlas of the mammals of Zimbabwe Rhodesia Mus. mem. Natl. mus. Moment Rhod 1979 9 1 147
Speakman J.R., Racey P.A., Plecotus auritus Fenton M.B., Racey P.A., Rayner J.M.V.Cambridge University Press 1987The energetics of pregnancy and lactation in the brown longeared bat In: Recent advances in the study of bats, Cambridge
Speakman J.R., Racey P.A.The doubly-labelled water technique for the measurement of energy expenditure in free-living animals Science Progress Oxford 1988a 72 227 237
Speakman J.R., Racey P.A.Validation of the doubly-labelled water technique in insectivorous bats Physiological Zoology 1988b 61 514 527
Speakman J.R., Nagy K.A., Masman D., Mook W.G., Poppitt S.D., Strathearn G.E., Racey P.A.Interlaboratory comparison of different analytical techniques for the determination of oxygen-18 abundance Analytical Chemistry 1990 62 703 708
Speakman J.R., Racey P.A., Burnett A.M.Metabolic and behavioral consequences of the procedures of the doubly-labelled water technique on white (MF1) mice Journal of Experimental Biology 1991 157 123 132
Studier E.H.Bioenergetics of growth, pregnancy, and lactation in the laboratory mouse. Comparative Biochemistry and Physiology 64A: 1979 473 481
Swanepoel P.The population dynamics of rodents at Pongola, northern Zululand, exposed to dieldrin cover spraying. Unpub. M.Sc. thesis, University of Pretoria 1972
Trayhurn P., Keith J.S., Racey P.A., Burnett A.M.Immunological identification of uncoupling protein in interscapular “brown” adipose tissue of suckling and adult pipistrelle bats “Pipistrellus pipistrellus. Comparative Biochemistry and Physiology 99B: 1991 317 320
Wong W.W., Klein P.D.A review of techniques for the preparation of biological samples for mass-spectrometric measurements of hydrogen-2/hydrogen-1 and oxygen-18/oxygen-16 isotope ratios Mass Spectrometry Reviews 1987 5 313 342
| All Time | Past 365 days | Past 30 Days | |
|---|---|---|---|
| Abstract Views | 2821 | 1005 | 17 |
| Full Text Views | 39 | 6 | 0 |
| PDF Views & Downloads | 7 | 0 | 0 |
Previous studies of the pouched mouse (Saccostomus campestris) have revealed that during reproduction there is no increase in food consumption, although resting energy demands, measured by respirometry, increase substantially. One explanation for this anomalous situation is that these mice may routinely use torpor to compensate their energy budgets.
We measured the daily energy expenditure of eleven individual pouched mice over three consecutive days using the doubly-labelled water technique. The mice were housed in cages where they had free access to food and water, at an average temperature of 26.5 °C, and exposed to a natural photoperiod (February Pretoria).
There was a large day-to-day variation in energy expenditure within each individual. The coefficient of variation in daily energy demand averaged 24.5%. By comparing the correlation of estimates for consecutive and nonconsecutive days we established that this variation was not a consequence of errors in the isotopic technique.
The scaling exponent of the measures of energy expenditure to mass was 1.196 (sd = 0.37: not significantly different to 1.0). We corrected all the estimates to a mean mass of 61.3 g using a scaling exponent of 1.0. We then compared the daily energy demands with expected energy requirements for endothermic animals at rest in respirometers. All the estimates of daily energy expenditure exceeded those anticipated from the resting costs, and averaged about 2.1× greater. We found no compelling evidence therefore that Saccostomus campestris routinely utilizes long (>8 hours) bouts of torpor to compensate its energy budget.
| All Time | Past 365 days | Past 30 Days | |
|---|---|---|---|
| Abstract Views | 2821 | 1005 | 17 |
| Full Text Views | 39 | 6 | 0 |
| PDF Views & Downloads | 7 | 0 | 0 |