Variation in abundance and habitat use of the critically endangeredMicrocebus gerpiacross its fragmented range

Abstract

A link between the abundance of species and their degree of ecological specialization has previously been suggested within the primate order. Many species of lemurs were only recently described and even basic ecological data are not yet available for them. We investigated the habitat use, abundance, and habitat characteristics of the critically endangered Microcebus gerpi and evaluated potential impacts of vegetation structure and human disturbances on variations in its abundance. We determined abundance by systematic nocturnal surveys along 13 transects that were also used for characterizing the vegetation structure in seven study sites that were widely distributed within its range. Although M. gerpi occurred in all studied lowland rainforest and littoral forest fragments in central eastern Madagascar and therefore has a higher ecological plasticity and wider distribution than previously thought, its actual Area of Occupancy is very small (339.78 km2) due to an extreme degree of habitat fragmentation throughout its range. M. gerpi occurred with a mean encounter rate of 3.04 individuals/km but abundance varied substantially between sites (0.75–4.5 individuals/km). Statistical modeling revealed that the cover of small‐ to medium‐sized trees had a positive impact on the abundance of M. gerpi, whereas a composite disturbance score (CDS), formed on the basis of information on the prominence of fires, cattle, charcoal production and wood extraction inside and around the forest, had a negative impact on abundance. These results suggest that M. gerpi is slightly less threatened than expected because of its larger geographic range, but also that it responds negatively to human disturbances. These findings raise strong conservation concerns and question the long‐term viability of the remaining small and isolated populations of this arboreal solitary forager.