Prolonged Torpor in Goodman's Mouse Lemur (Microcebus lehilahytsara) from the High-Altitude Forest of Tsinjoarivo, Central-Eastern Madagascar.

Abstract

The nocturnal mouse and dwarf lemurs from Madagascar are known to express heterothermy. Whereas dwarf lemurs (Cheirogaleus) are obligate hibernators, mouse lemurs (Microcebus) can express a great range of heterothermic responses, including daily torpor, prolonged torpor or hibernation, depending on the species, population or individual. Although there is indirect evidence of heterothermy in a handful of mouse lemur species, direct physiological confirmation is currently limited to four: Microcebus berthae(dry forest), M. ravelobensis(dry forest), M. griseorufus(spiny forest), M. murinus(dry forest/littoral forest). We studied Goodman's mouse lemurs (M. lehilahytsara) at the high-altitude rain forest of Tsinjoarivo, central-eastern Madagascar. We captured a total of 45 mouse lemurs during pre- and post-torpor seasons. We recorded body mass and measured tail base circumference, which was used as proxy for fattening. Moreover, using telemetry, we obtained sporadic skin temperature data from a mouse lemur female between March and June. From June 9 to 16, we performed more intensive data sampling and thereby confirmed the expression of prolonged torpor in this female, when skin temperatures consistently displayed values below 25°C for more than 24 h. We documented 3 torpor bouts, 2 of which were interrupted by naturally occurring arousals. Torpor bout duration ranged from approximately 47 to maximally about 69 h. We found similarities between the Goodman's mouse lemur torpor profile and those known from other species, including the fact that only a portion of any mouse lemur population deposits fat stores and undergoes torpor in a given year. The variable expression of heterothermy in Goodman's mouse lemurs contrasts with obligatory hibernation displayed by two sympatric species of dwarf lemurs, suggesting cheirogaleids use a range of metabolic strategies to cope with seasonality and cold environments.