Habitat use, selection, and population density of chameleon communities (Calumma spp.) in the fragmented central highlands forests of Madagascar

The Central Highlands forests of Madagascar are critical habitats for a diverse faunal assemblage, including reptiles. These forests, once extensive and connected, are now fragmented with substantial degradation. As a result, the many sensitive and threatened species residing in these remaining forest fragments are at risk of local extirpation. Without targeted evaluation of suitable remaining habitat, as well as an understanding of species’ tolerances to changes in this habitat, it is impossible to predict population persistence. To assess the impacts of forest fragmentation across potentially sensitive species, we examined the local abundance and microhabitat selection of an endemic Malagasy chameleon assemblage (Chamaeleonidae: Calumma) across three forest patch remnants in the Central Highlands. We estimated population sizes and densities of four sympatric taxa, Calumma crypticum, C. gastrotaenia, C. globifer, and the C. nasutum group. Our results revealed that abundance is influenced by seasonal variation and that population structure is female-biased for all four species. Surprisingly, despite being threatened species due to population fragmentation and declines, C. globifer was abundant during wet season, with high densities in some forest patches (up to 88 individuals/ha). We identified spatial and temporal niche overlap among all four species, with niche preference strongly partitioned by roost site preference with evidence of vertical stratification. Chameleon community structure within these forest patches appears to be primarily driven by microhabitat use and, to a lesser extent, overall habitat type. Population responses to rapid land-use change and overall habitat fragmentation within the remaining Central Highlands forests require further demographic studies to best inform future management and conservation strategies.