Twenty-one species of mouse lemurs are now recognized in Madagascar (Radespiel et al., 2012; Rasoloarison et al., 2013). They live in a wide variety of habitats, from the xerophytic forests of the south and southwest (Yoder et al., 2002; Rasoazanabary, 2004; Génin, 2008, Kobbe and Dausmann, 2009) to the dry deciduous forests of the west and north (Ganzhorn and Schmid, 1998; Schmid and Kappeler, 1998; Zimmermann et al., 1998), and to the low-, mid-, and high-altitude rainforests of the east (Atsalis, 1999; Lahann et al., 2006; Radespiel et al., 2008, 2012; Gligor et al., 2009; Blanco, 2011). Mouse lemurs do not live in high-altitude Erica-dominated heathland.
The xerophytic (or “spiny”) forests of southwestern Madagascar are some of the driest and most seasonal environments in all of Madagascar (Ratsirarson et al., 2001; Fenn, 2003; Génin, 2008; Kamilar and Muldoon, 2010). Dewar and Richard (2007) give it high marks for “unpredictability” – both in terms of month-to-month and year-to-year variation. Succulent, dry-loving plants belonging to the families Didiereaceae and Euphorbiaceae dominate the xerophytic bush of the Spiny Thicket Ecoregion (Fenn, 2003; Burgess et al., 2004). Only one species of mouse lemur thrives in these habitats, Microcebus griseorufus.
Among the western mouse lemur species, Microcebus murinus is the best studied. It has a broad geographic distribution and has been hailed as wide-niched. It lives in sympatry with other mouse lemur species that appear to have much narrower habitat preferences, including M. bongolavensis in the north (Radespiel et al., 2008), M. ravelobensis in the northwestern dry deciduous forest of Ampijoroa (Zimmermann et al., 1998), and M. berthae in the western dry deciduous forest of Kirindy (Schmid and Kappeler, 1994; Schwab and Ganzhorn, 2004). It also lives in sympatry with M. griseorufus in the southern dry forest of Berenty (Yoder et al., 2002) and the southeastern humid forest at Andohahela (Rakotondranary and Ganzhorn, 2011). At Kirindy, M. murinus prefers the moister forest habitats bordering the Kirindy River (Yoder et al., 2002; Rasoazanabary, 2006), and at Berenty Private Reserve, it avoids xerophytic forest (Yoder et al., 2002). In southeastern Madagascar, there is evidence of hybridization between M. griseorufus and M. murinus in the transitional forest corridor connecting the xerophytic forests (with M. griseorufus) located west of Ampihamy to the wetter littoral forests (with M. murinus) located east of Sarikady (Gligor et al., 2009).