Revista Chilena de Historia Natural 78 (2): 199-206, 2005
RESEARCH ARTICLE
Energetics, thermoregulation and torpor in the Chilean mouse-opossum Thylamys
elegans (Didelphidae)
In this paper we studied the energetics and thermoregulation of the Chilean mouse-
opossum Thylamys elegans (Dielphidae) a nocturnal small marsupial, endemic of southern South America. We studied
their standard energetic and determined whether they exhibit shallow daily torpor or deep prolonged torpor as a function
of ambient temperature and food availability. Thylamys elegans partially supports the hypothesis that
Neotropical marsupials have somewhat a higher basal metabolic rate (BMR) and thermal conductance (Cm) than
Australian ones. In fact, BMR was higher but Cm was lower than expected for their body mass. The higher mass-
independent BMR of the Chilean mouse-opossum may be explained by its insectivorous food habits and its low Cm by its
temperate habitats. Euthermic Chilean mouse-opossum showed daily fluctuations in body temperature being significantly
higher during night time. In addition T. elegans entered in daily torpor and aroused spontaneously only was
food was absent. That is, this species display a facultative type of daily torpor because propensity to enter in torpor was
dependent of the combination of food absence and low ambient temperature. No torpor was observed when food was
available. During torpor ambient temperature was slightly above ambient temperature between 0.3 to 0.5 °C. Torpor in this
species as well as in marsupials in general, appears to be a flexible and an opportunistic response to unpredictable
environmental conditions.
Key words:
South America, Chile,
marsupials, energetic, thermoregulation, facultative torpor
