Browsing by Author "Ruiz, G"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Energetics and torpor of a South American "living fossil", the microbiotheriid Dromiciops gliroides
    (2004) Bozinovic, F; Ruiz, G; Rosenmann, M
    We examined the energetics of the living fossil microbiotheriid Dromiciops gliroides, a nocturnal and rare small marsupial, endemic to the northern portion of the temperate forest of southern South America. We investigated the effects of changes at ambient temperature and food restriction on the energetics and patterns of torpor. We determined whether they exhibit shallow daily torpor or deep prolonged torpor like some Australian marsupials. Thermal conductance was 92.5% of the expected value for a similarly sized eutherian and basal metabolic rate was 82.9 and 58.6% of the predicted value for standard metatherians and eutherians, respectively. Euthermic D. gliroides showed daily fluctuations in body temperature, being significantly higher during the night. Dromiciops gliroides entered torpor and aroused spontaneously. The duration of torpor bouts increased in response to decreasing ambient temperature; torpor bout duration ranged from 10 h at 20degreesC to 120 h at 12.5degreesC. This study is the first record of deep torpor or hibernation for a South American mammal. Torpor in this species as well as in marsupials in general appears to be an opportunistic response to unpredictable biotic and abiotic conditions.
  • No Thumbnail Available
    Item
    Energetics thermoreoulation and torpor in the Chilean mouse-opossum Thylamys elegans (Didelphidae)
    (2005) Bozinovic, F; Ruiz, G; Cortés, A; Rosenmann, M
    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 (C-m) than Australian Ones. In fact, BMR was higher but C-m 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 C-m by its temperate habitats. Euthermic Chilean mouse-opossum showed daily fluctuations in body temperature being significantly hi-her 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 degrees 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.