title: Hypothermia versus torpor in response to cold stress in the native Australian mouse Pseudomys hermannsburgensis and the introduced house mouse Mus musculus.
abstract: This study compared torpor as a response to food deprivation and low ambient temperature for the introduced house mouse (Mus musculus) and the Australian endemic sandy inland mouse (Pseudomys hermannsburgensis). The house mouse (mass 13.0+/-0.48 g) had a normothermic body temperature of 34.0+/-0.20 degrees C at ambient temperatures from 5 degrees C to 30 degrees C and a basal metabolic rate at 30 degrees C of 2.29+/-0.07 mL O2 g(-1) h(-1). It used torpor with spontaneous arousal at low ambient temperatures; body temperature during torpor was 20.5+/-3.30 degrees C at 15 degrees C. The sandy inland mouse (mass 11.7+/-0.16 g) had a normothermic T(b) of 33.0+/-0.38 degrees C between T(a) of 5 degrees C to 30 degrees C, and a BMR of 1.45+/-0.26 mL O2 g(-1) h(-1) at 30 degrees C. They became hypothermic at low T(a) (T(b) about 17.3 degrees C at T(a)=15 degrees C), but did not spontaneously arouse. They did, however, survive and become normothermic if returned to room temperature (23 degrees C). We conclude that this is hypothermia, not torpor. Consequently, house mice (Subfamily Murinae) appear to use torpor as an energy conservation strategy whereas sandy inland mice (Subfamily Conilurinae) do not, but can survive hypothermia. This may reflect a general phylogenetic pattern of metabolic reduction in rodents. On the other hand, this may be related to differences in the social structure of house mice (solitary) and sandy inland mice (communal).
authors.affiliation: Zoology, School of Animal Biology MO92, University of Western Australia, 35 Stirling Highway, Crawley, Perth, Western Australia 6009, Australia. tomlis01@student.uwa.edu.au
authors.forename: Sean
authors.initials: S
authors.lastname: Tomlinson
authors.forename: Philip C
authors.initials: PC
authors.lastname: Withers
authors.forename: Christine
authors.initials: C
authors.lastname: Cooper
mesh_terms: D000064:Acclimatization; D000818:Animals; D001143:Arousal; D001481:Basal Metabolism; D001522:Behavior, Animal; D001831:Body Temperature; D002940:Circadian Rhythm; D003080:Cold Temperature / Q000009:adverse effects*; D005508:Food Deprivation; D007035:Hypothermia / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology*; D053609:Lethargy / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D051379:Mice; D010101:Oxygen Consumption; D012919:Social Behavior; D013045:Species Specificity; D014904:Western Australia