title: The role of basking in the development of endothermy and torpor in a marsupial.
abstract: Marsupials have a slow rate of development and this allows a detailed examination of thermoregulatory developmental changes and stages. We quantified the cooling rates of marsupial dunnarts (Sminthopsis crassicaudata) at 40-56 days (d) old, and torpor and basking behaviour in animals given the option to bask in four age groups from 60 to 150 d. The development of thermoregulation was a continuum, but was characterised by three major thermoregulatory stages: (1) at 40 d, animals were unable to maintain a constant high body temperature during short-term cold exposure; (2) at 60 d, animals could maintain a high Tbfor the first part of the night at an ambient temperature of 15.0 ± 0.7 °C; later in the night, they entered an apparent torpor bout but could only rewarm passively when basking under a heat lamp; (3) from ~90 d, they expressed prolonged torpor bouts and were able to rewarm endogenously. Young newly weaned 60 d animals were able to avoid hypothermia by basking. In this case, basking was not an optional behavioural method of reducing the cost of rewarming from torpor, but was essential for thermoregulation independent of the nest temperature. Results from our study suggest that basking is a crucial behavioural trait that permits young marsupials and perhaps other juvenile altricial mammals to overcome the developmental stage between poikilothermy early in development and full endothermy later in life.
authors.affiliation: Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, 2351, Australia. cwacker4@gmail.com.
authors.forename: Chris B
authors.initials: CB
authors.lastname: Wacker
authors.affiliation: Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, 2351, Australia.|Physiology, School of Medical Sciences, Bosch Institute, The University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Bronwyn M
authors.initials: BM
authors.lastname: McAllan
authors.affiliation: Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, 2351, Australia.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Körtner
authors.affiliation: Centre for Behavioural and Physiological Ecology, Zoology, University of New England, Armidale, NSW, 2351, Australia.
authors.forename: Fritz
authors.initials: F
authors.lastname: Geiser
mesh_terms: D000367:Age Factors; D000818:Animals; D001481:Basal Metabolism; D001522:Behavior, Animal; D004734:Energy Metabolism; D004777:Environment; D008394:Marsupialia / Q000145:classification / Q000254:growth & development* / Q000523:psychology; D009043:Motor Activity; D022722:Thermogenesis; D013997:Time Factors; D064348:Torpor
keywords: Basking; Development; Marsupial; Sminthopsis; Thermal energetics; Torpor