Torpor in free-ranging antechinus: does it increase fitness?
Antechinus are small, insectivorous, heterothermic marsupial mammals that use torpor from late summer to early winter and reproduce once a year in late winter/early spring. Males die after mating, most females produce only a single litter, but some survive a second winter and produce another litter. As it is not known how these females manage to survive the second winter after the energetically demanding reproductive period and then reproduce a second time, we aimed to provide the first data on thermal biology of free-ranging antechinus by using temperature telemetry. Male Antechinus stuartii and Antechinus flavipes rarely entered torpor in autumn/early winter in the wild, expressing only shallow bouts of <2 h. Female A. stuartii used torpor extensively, employing bouts up to 16.7 h with body temperatures as low as 17.8 °C. Interestingly, although first and second year females used similar torpor patterns, torpor occurrence was almost twofold in second year (93 % of days) than first year females (49 %), and the proportion of the overall monitoring period animals spent torpid was 3.2-fold longer in the former with a corresponding shorter activity period. Our study suggests that intensive use of torpor is crucial for second year females for autumn and winter survival and production of a second litter. We provide the first evidence of an age-related pattern in daily torpor expression in free-ranging mammals and show that torpor use is a complex process that is affected not only by the current energy availability and thermal conditions but also by the reproductive history and age of individuals.
Centre for Behavioural & Physiological Ecology, Zoology, University of New England, Armidale, NSW, 2351, Australia, arojas2@myune.edu.au.
A Daniella
AD
Rojas
Gerhard
G
Körtner
Fritz
F
Geiser
D000818:Animals; D005260:Female; D008297:Male; D008394:Marsupialia / Q000502:physiology*; D012098:Reproduction / Q000502:physiology*; D064348:Torpor / Q000502:physiology*