Lemurs in a dying forest: Factors influencing lemur diversity and distribution in forest remnants of north-eastern Madagascar

A majority of Madagascar's iconic lemurs (Primates, Strepsirrhini) is threatened with extinction due to anthropogenic activities like land use change (deforestation) and bushmeat hunting. We used a multivariate approach combining land cover mapping, vegetation/degradation monitoring, the degree of anthropogenic disturbance and the status of forest protection by the local community to model their impact on lemur diversity, population densities and encounter rates within a rural area of lowland rain forest in north-eastern Madagascar. High mean annual deforestation rates (2.4%) were calculated since 1990, resulting in a landscape of small and isolated forest fragments. A limited number of eight lemur species belonging to five lemur families were encountered. Diurnal species were absent, while cathemeral lemurs avoided human disturbance. Small and nocturnal species were relatively abundant. Overall lemur diversity was best explained by forest size and a combination of disturbance and hunting. Encounter rates of three nocturnal taxa were influenced by forest size and habitat degradation. Community-level forest protection had no effect on lemur diversity, but coincided with lower levels of habitat degradation. Lemur population sizes were relatively small and only few forests remain that offer suitable habitats for viable populations. We highly recommend external conservation NGOs to support local forest management by improving the existing community-based approach. Actions should include expansion of protected habitats to increase population connectivity (reforestation) and to decrease lemur disturbance by villagers. Without external support, the last remaining forest habitats will be devastated within a few years resulting in the local extinction of most lemur populations.