Bioenergetics of torpor in the Microbiotherid marsupial, Monito del Monte (Dromiciops gliroides): the role of temperature and food availability
- 266 Downloads
Torpor is the physiologically controlled reduction of metabolic rate and body temperature experienced by small birds and mammals when facing periods of low temperature and/or food shortage. In this study, we provide a first quantitative description of torpor in the relict marsupial Dromiciops gliroides by: (1) characterizing body temperature (T B) and torpor patterns, (2) evaluating the combined effects of ambient temperature and different levels of food restriction on torpor incidence and (3) exploring the metabolic depression during torpor. D. gliroides exhibited short bouts of torpor on a daily basis, during which T B decreased close to ambient temperature. During the active phase, T B also exhibited pronounced variation (range 34–38°C). In order to evaluate the consistency of torpor, we computed the repeatability of T B. Using the whole dataset, repeatability was significant (τ = 0.28). However, when torpid individuals were excluded from the analysis, repeatability was non-significant: some individuals were more prone to experience torpor than others. Our results indicate that this species also exhibits short bouts of daily torpor, whose depth and duration depends on the joint effects of T A and food availability. At T A = 20°C, the maximum torpor incidence was found at 70–80% food reduction, while at both extremes of the food continuum (100 and 0–10% food reduction) individuals were completely active, although considerable variation in T B was recorded. At T A = 10°C, individuals developed a deep form of torpor that was independent of the amount of food provided. On average, torpid D. gliroides reduced their metabolic rate up to 92% of their active values. In general, our results suggest that T A was the most immediate determinant of torpor, followed by energy availability.
KeywordsTorpor Repeatability Energetics Thermoregulation Dromiciops
This work was funded by FONDECYT grant No 1090423. Animal maintenance and capture were performed according current Chilean law, and SAG permit No 444-2007. We would like to thank reviewers for comments that greatly improved the manuscript.
- Arlettaz R, Ruchet C, Aeschimann J, Brun E, Genoud M, Vogel P (2000) Physiological traits affecting the distribution and wintering strategy of the bat Tadarida teniotis. Ecology 81:1004–4014Google Scholar
- Bozinovic F, Ruiz G, Cortes A, Rosenmann M (2005) Energetics, thermoregulation and torpor in the Chilean mouse-opossum Thylamys elegans (Didelphidae). Rev Chil Hist Nat 78:199–206Google Scholar
- Buck CL, Barnes BM (2000) Effects of ambient temperature on metabolic rate, respiratory quotient, and torpor in an arctic hibernator. Am J Physiol 279:R255–R262Google Scholar
- Geiser F, Ruf T (1995) Hibernation versus daily torpor in mammals and birds: physiological variables and classification of torpor patterns. Physiol Biochem Zool 68:935–966Google Scholar
- Marin-Vial P, Gonzalez-Acuna D, Celis-Diez JL, Cattan PE, Guglielmone AA (2007) Presence of Ixodes neuquenensis Ringuelet, 1947 (Acari: Ixodidae) on the endangered Neotropical marsupial Monito del Monte (Dromiciops gliroides Thomas, 1894, Microbiotheria: Microbiotheriidae) at Chiloe Island, Chile. Eur J Wildl Res 53:73–75CrossRefGoogle Scholar
- McKenna MC, Bell CJ (1997) Classification of mammals above the species level. Columbia University Press, New YorkGoogle Scholar
- McNab BK (2005) Uniformity in the basal metabolic rate of marsupials: its causes and consequences. Rev Chil Hist Nat 78:183–198Google Scholar
- Quinn GP, Keough MJ (2002) Experimental design and data analysis for biologists. Cambridge University Press, CambridgeGoogle Scholar
- StatSoft (2006) INC. STATISTICA (data analysis software system) version 6.1Google Scholar