A population survey of sympatric cheirogaleids in southwestern Madagascar

Zombitse-Vohibasia National Park harbours a species-rich but understudied lemur community in southwestern Madagascar. Local population estimates are dated or absent for its four sympatric species of Cheirogaleidae: the grey mouse lemur (Microcebus murinus), Coquerel's giant mouse lemur (Mirza coquereli), fat-tailed dwarf lemur (Cheirogaleus medius) and pale fork-marked lemur (Phaner pallescens). To provide local density and encounter rate estimates for these cheirogaleids, we conducted line transect surveys in the Zombitse sector of the National Park over a three-week period in December 2018–January 2019. We calculated densities of 37.4 Mir. coquereli individuals/km² (95% CI = 20.4–68.6) and 230.8 C. medius individuals/km² (95% CI = 172.6–308.6). Our results highlight the conservation importance of Zombitse-Vohibasia as a stronghold for these restricted and threatened species. The sample sizes for Mic. murinus and P. pallescens were insufficient for generating population estimates. Considering that Microcebus spp. are typically amongst the most abundant mammals at a given site, further studies are needed to investigate and verify this apparent scarcity.