1Ramanamanjato and Ganzhorn, 2001; 2 Ganzhorn, 1995; 3 Goodman and Rasolonandrasana, 2001; 4 Ganzhorn, 1987; 5 Ganzhorn et al., 1997; 6 Rasoloarison et al., 2000; 7 Hawkins et al., 1998; 8 Schwab and Ganzhorn, 2004; 9 Rendigs et al., 2003; 10 Zimmermann et al., 1998; 11 Ratsirarson and Ranaivonasy, 2002; 12 Irwin et al., 2001; 13Rasoazanabary, 2004; 14Irwin et al., 2000; 15 Goodman and Schütz, 2000;
16Rakotondravony and Radespiel, unpublished data; 17Hawkins, 1999; 18Randrianarisoa et al., 1999; 19 Rauh, 1992; 20 Sterling and Ramaroson, 1996; 21Duckworth etal., 1995; 22Jolly etal., 2002; 23Yoder et al., 2002.
some species have been found in as many as five different broad habitat types and over a rainfall and altitude gradient (M. murinus, M. rufus group), others have been observed in only one (M. berthae) or two (M. myoxinus) types of forest and seem to lack environmental gradients within their distribution range. However, an interpretation of these findings in terms of higher or lower adaptive flexibility seems to be too premature, since (1) habitat classifications provided in publications are usually very broad, and (2) habitat diversity may also correlate with the number of studies conducted on the respective species. A literature search performed in the Database PrimateLit (http://primatelit.library.wisc.edu/) with scientific species names as search variables revealed a significant positive correlation between the time span since the first record (in years) and the number of hits for each species (range of time span: 5-61 years, range of hits: 25-1389; Spearman rank correlation: r = 0.913, n = 8, p <0.05).
Detailed studies on microhabitat characteristics were so far performed only on three mouse lemur species occurring in sympatric pairs in Kirindy (M. murinus and M. berthae) and Ampijoroa (M. murinus and M. ravelobensis). These studies revealed species-specific differences between used and unused microhabitats in all three species, although the findings were ambivalent for M. murinus. In some studies M. murinus was positively associated with microhabitats in relatively intact primary and diverse forest types (Ganzhorn and Schmid, 1998; Ramanamanjato and Ganzhorn, 2001; Rendigs et al., 2003). Other studies indicated that M. murinus may not be very specialized (Schwab and Ganzhorn, 2004), may well survive in disturbed forests (Ganzhorn, 1995; Radespiel and Raveloson, 2001), and occurs even in secondary growth (Ganzhorn and Schmid, 1998) or plantations (Ganzhorn, 1987), although reproductive success and therefore long-term population viability may be reduced under these highly disturbed circumstances. Whereas the first line of argument suggests a considerable vulnerability of M. murinus to human disturbances and therefore has important conservation implications, the second line of reasoning implies only low conservation priority for this species. Further studies are urgently needed to decide which of these contradictory conclusions most accurately describes the ecological requirements of this species.
M. berthae was concluded to possess high habitat specificity due to its high affinities to vines (used as sleeping sites) and to relatively open forest in the intermediate layer at 1.6-6.0 m (Schwab and Ganzhorn, 2004). This specificity was taken to explain the small distribution range of this species as well as its vulnerability toward being outcompeted by its larger sister species M. murinus which occurs in the same area.
Similar to M. berthae, M. ravelobensis seems to show a preference for vines (also used as sleeping sites) and was furthermore associated with relatively open microhabitats (i.e., higher cover of herb layer [Rendigs et al., 2003]). In a further study, these findings were interpreted as signs of ecological differentiation between the golden-brown and the sympatric grey mouse lemur in Ampijoroa, since they coincide well with species-specific sleeping site ecology (see below, Radespiel et al.,
2003a). The general applicability of these findings needs to be tested by examining more populations from different origins for each of these species.
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