Distribution and abundance of a critically endangered lemur species, Microcebus gerpi, in eastern Madagascar: a preliminary study

The critically endangered GERP’s Mouse Lemur (Microcebus gerpi) was so far only known from one single location (Sahafina), a small forest patch of lowland rainforest in eastern Madagascar. The goal of this study was therefore to study for the first time the distribution, abundance and the ecology of this largely understudied and threatened lemur species. In particular, we aimed to (1) determine the limits of the distribution of M. gerpi, (2) estimate its abundance throughout its distribution boundaries, (3) determine its sensitivity to habitat degradation, and (4) formulate recommendations for an effective conservation of the GERP’s mouse lemur in view of intensified land use strategies and habitat loss. A total of seven sites, including three littoral forest sites (1 to 17 m a.s.l.) and four low to mid altitude montane forest sites (29 to 487 m a.s.l.) were visited between August and December 2018, and systematic census observations, capture sessions, and habitat characterization were carried out in each of them. Microcebus gerpi was present in all sites between the rivers Ivondro and Mangoro and its abundance ranges from 2.1 to 5.8 individuals per ha. It showed no clear general response to habitat fragmentation or disturbance. However, this species was found in higher abundance in less disturbed and protected habitats. In contrast, it had its lowest abundance in the long-term disturbed littoral forest and in a less disturbed montane forest which is bordered by slash-and-burn cultivation. Based on lemur census results and the general condition of the habitats, the Sahafina Forest is the most appropriate among all sites for the conservation of M. gerpi, but requires effective protection measures to assure the long-term survival of viable mouse lemur populations in this highly fragmented landscape. Moreover, sustainable development actions should be undertaken in this region in order to minimize the forest loss.