Distribution, Population Structure and Habitat Use of Microcebus berthae Compared to Those of Other Sympatric Cheirogalids.

We aimed to identify the geographical and biotic limitations of Microcebus berthae , the smallest extant primate. Furthermore we analyzed the mating system of two local populations and their habitat use in relation to microhabitat structures and to those of Microcebus murinus and Cheirogaleus medius , two potentially competing lemur species. The range of Microcebus berthae is restricted to ≤220 km[sup 2] in the dry deciduous forest of western Madagascar. A very optimistic estimate of the total population size is ca. 7900 individuals. During a 13-mo mark-recapture study individuals were trapped from May 1995 to May 1996 at permanent trap locations 50 m apart over 2 study areas of ca. 25 ha each. The spacing of trap locations where individuals have been retrapped indicate that males have larger home ranges than those of females, which in concert with multiple intra- and intersexual range overlap indicates a promiscuous mating system. In contrast to the other 2 species, Microcebus berthae maintained specific habitat utilization patterns at 2 sites with different vegetation structures. Their habitat use in relation to vegetation characteristics differed from that of Cheirogaleus medius but not from that of Microcebus murinus . Co-occurrence patterns of Microcebus berthae and M. murinus deviated significantly from random and resembled a checkerboard distribution possibly generated by competitive exclusion. Thus, according to the niche concept, Microcebus berthae seem to be separated from Cheirogaleus medius by differences in food composition and habitat requirements, while they avoid direct competition with M. murinus by spatial separation. [ABSTRACT FROM AUTHOR]