Fragmentation effects in sympatric mouse lemurs (Microcebus spp.) in northwestern Madagascar

Habitat loss and fragmentation are among the most important factors threatening biodiversity worldwide. In Madagascar, forty-four percent of the native forest has been lost over the six last decades, but the effects of forest fragmentation on fauna are still not well understood. This study investigates how forest fragmentation affects the distribution and abundance of two species of mouse lemurs, Microcebus murinus and M. ravelobensis, in two fragmented landscapes, the Ankarafantsika National Park (ANP) and the Mariarano region. Field work was conducted in a total of 40 forest fragments and in 12 sites in adjacent continuous dry deciduous forest. Mouse lemurs were captured with Sherman traps (11,166 trap nights) that were installed three times along all each forest transect during twodry seasons (2017 and 2018). Whereas species representation in the continuous forest differed largely between the two landscapes, species representation was generally similar within the forest fragments in each region. The number of M. ravelobensis caught were positively correlated with the size of the forest when scaled by trapping effort (R2=0.354, n=52, p<0,01). However, there was neither a correlation between the number of M. murinus captured and forest size (R2=0.035, n= 52, n.s), nor between the number of captured animals of both species (R2=0.034, n=52, n.s). Species differences might be explained by different ecological niches and/or a different vagility. These results show mixed effects of forest fragmentation on mouse lemurs in northwestern Madagascar. Thus, maintaining large and diverse areas of forest is therefore important for their conservation and long-term survival.