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 (<i>Cheirogaleus</i>) are obligate hibernators, mouse lemurs (<i>Microcebus</i>) 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: <i>Microcebus berthae</i>(dry forest)<i>, M. ravelobensis</i>(dry forest), <i>M. griseorufus</i>(spiny forest)<i>, M. murinus</i>(dry forest/littoral forest). We studied Goodman’s mouse lemurs (<i>M. lehilahytsara</i>) 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.

Seasonal Differences in the Encounter Rate of the Fat-Tailed Dwarf Lemur (Cheirogaleus medius) in the Transitional Forests of Northwest Madagascar: Implications for Reliable Population Density Assessment

“…This is a well-known trait in mouse lemurs (genus Microcebus) (Kobbe et al, 2011;Lovegrove et al, 2014;Ortmann et al, 1997;Schmid, 2000), but it also occurs in the Javan slow loris (Nycticebus javanicus), the African lesser bushbaby (Galago moholi), the hairy-eared dwarf lemur (Allocebus trichotis), and possibly Coquerel's giant mouse lemur (Mirza coquereli) (Dausmann, 2014;Dausmann & Warnecke, 2016;Nowack et al, 2010). However, some strepsirrhines, such as the dwarf lemurs of the Cheirogaleus genus (Dausmann & Warnecke, 2016), the pygmy slow loris (N. pygmaeus) (Ruf et al, 2015), Goodman's mouse lemur (M. lehilahytsara) (Andriambeloson et al, 2020), the reddish-gray mouse lemur (M. griseorufus) (Kobbe et al, 2011), and the brown mouse lemur (M. rufus) (Atsalis, 1999) enter torpor for prolonged periods of several days or months (hibernation) if they are able to store enough energy reserves. Studying such species is therefore difficult, because they are inactive and undetectable for long periods of the year.…”

Morphological variability or inter‐observer bias? A methodological toolkit to improve data quality of multi‐researcher datasets for the analysis of morphological variation

“…Several mouse lemur species (e.g., M. berthae and M. murinus at Kirindy, Schmid, 2000; M. griseorufus , Génin, 2008; M. lehilahytsara , Randrianambinina et al, 2003, Andriambeloson et al, 2020; M. ravelobensis , Thorén et al, 2011; M. rufus , Atsalis, 1999, Ramananjato et al, 2022) can cope with thermoregulatory challenges under low temperatures using torpor or even hibernation (Blanco et al, 2018; Salewski & Watt, 2016). This may help to explain why more than 78% of the variation in body mass and body length could not be explained by climatic factors.…”

“…Phylogenetic constraints on body size are indicated by the observation that several smaller taxa ( M. berthae, M. myoxinus, M. lehilahytsara, M. rufus ) form a distinctive clade of small‐bodied mouse lemur species (Louis & Lei, 2016), that can occur not only in sympatry with other larger species but also across a variety of environments in eastern and western Madagascar. These include the highly seasonal western dry deciduous forests with their clear separation into a hot rainy season (4–6 months) and a cooler dry season lacking precipitations almost entirely (6–8 months), the central highlands that undergo substantial seasonal temperature fluctuations, and the eastern lowland rainforests that exhibit the least climatic variations across the year (Andriambeloson et al, 2020; Blanco et al, 2015; Evasoa et al, 2018). A comprehensive evaluation of the relative impact of environmental variables and phylogenetic constraints on the morphology of mouse lemurs is currently hampered by a lack of a fully resolved phylogeny of all currently described mouse lemur lineages.…”

Population genomic structure in Goodman’s mouse lemur reveals long-standing separation of Madagascar’s Central Highlands and eastern rainforests

“…If M. lehilahytsara has adaptive traits that allowed the species to expand its range into the CHS while related species were restricted to lowland forests, M. lehilahytsara may have been more robust to Pleistocene climate change and even more recent anthropogenic disturbances. M. lehilahytsara has been regarded as a highland specialist (Radespiel et al, 2012) and has been documented to be able to enter a state of prolonged torpor (Blanco et al, 2017;Andriambeloson et al, 2020). We hypothesize that the capacity for extended torpor in M. lehilahytsara is an adaptive trait that has facilitated its increased geographic range compared to most other mouse lemur species.…”