Cheirogaleid distribution in western Madagascar

The largest remaining tract of western dry deciduous forest in Madagascar is located in the region of Menabe Central and harbors a species-rich lemur community. The distribution and abundance of lemur species have never been assessed across the forests of the Menabe Central. We therefore surveyed populations of three species of the family Cheirogaleidae (Cheirogaleus medius, Mirza coquereli, Phaner pallescens) via distance sampling on 35 1-km line transects to estimate overall population densities and to investigate the regional distribution against the backdrop of anthropogenic activities.

Corresponding to species-specific ecological demands, we documented divergent spatial population structures for the three species across Menabe Central. Cheirogaleus medius occurred in comparably high population densities in all forest regions, whereas the abundance of M. coquereli and P. pallescens was substantially lower and their distribution more heterogeneous. Moreover, regional distribution patterns revealed differential susceptibilities to human impact: C. medius largely relies on non-degraded habitat and both C. medius and P. pallescens avoid human environments spatially. In contrast to results of earlier studies, M. coquereli appeared to be fairly resilient to disturbances.

Thus, this cheirogaleid assemblage varied in composition
across heterogeneous habitats and was deprived where anthropogenic pressure was particularly intense. In order to prevent biodiversity loss in Menabe Central, effective protection of Kirindy and Ambadira Forests, and the narrow remaining forest corridor connecting them, will be crucial.