Greater ecological flexibility in furry-eared dwarf lemurs versus sympatric Sibree's dwarf lemurs: Insights from tree-hole, nest, and underground occupancy.

Abstract

Wild primates spend a significant portion of their lives in resting sites that are critical for survival, providing protection from predators and against weather extremes. The small-bodied and heterothermic dwarf lemurs (Cheirogaleus spp.) inhabit diverse environments in Madagascar, where they face high predation risk and thermoregulatory constraints. These lemurs variably use nests and tree holes as resting sites, and tree holes and underground locations as hibernacula, depending on the species and habitat. Here, we compare resting-site ecology in the sympatric Sibree's (C. sibreei) and furry-eared (C. crossleyi) dwarf lemurs at Tsinjoarivo forest. Whereas C. sibreei is an ecological specialist restricted to the cold rainforests of eastern Madagascar above 1500 m, C. crossleyi is an ecological generalist widely distributed across the eastern rainforests and forest fragments of the central highlands. We collate data collected between 2007 and 2019 on a total of 62 radio-collared dwarf lemurs tracked at different times of the year. We demonstrate that C. sibreei exclusively used tree holes as resting sites, showed greater resting-site fidelity, began hibernating earlier in the season, and only showed evidence of torpor once underground. In contrast, C. crossleyi occupied more and diverse resting sites in the active season, including tree holes, nests, and even exposed branches, and entered hibernation later, with many individuals expressing torpor while in nests, i.e., before switching to underground hibernacula. Adapted to cold rainforests, C. sibreei prioritizes resting sites with greater thermal insulation and a long, stable hibernation season of up to seven months. C. crossleyi opts for greater flexibility in both resting-site ecology and torpor expression. Although Tsinjoarivo is likely the coldest habitat occupied by C. crossleyi, perhaps pushing this species to the limits of their thermal tolerance, their ecological flexibility may give them a competitive edge over C. sibreei given ongoing habitat degradation at this site.