Habitat use by the island lemurs of Nosy Be, Madagascar

Abstract

Madagascar's lemurs are threatened by forest loss, fragmentation, and degradation. Many species use flexible behaviors to survive in degraded habitat, but their ability to persist in very small areas may be limited. Insular lemurs, like those found on Nosy Be, an island off the northwestern coast of Madagascar, are at heightened risk of sudden population declines and extirpation. Nosy Be is home to two Critically Endangered species—the endemic Nosy Be sportive lemur (Lepilemur tymerlachsoni) and Claire's mouse lemur (Microcebus mamiratra)—as well as the Endangered black lemur (Eulemur macaco). Most of the remaining forest on Nosy Be is protected by the 862‐ha Lokobe National Park. To document how Nosy Be lemurs use their restricted habitat, we conducted vegetation and reconnaissance surveys on 53 transects in and around Lokobe. We collected data on tree size, canopy cover, understory visibility, and elevation for 248 lemur sightings. We used a spatially explicit, multi‐species occupancy model to investigate which forest‐structure variables are important to lemurs. Our results represent some of the first data on habitat use by insular lemurs. Black lemurs preferred significantly larger trees and areas with less dense understory. They also occurred significantly less outside of Lokobe National Park, even when accounting for sampling effort and geography. The distributions of the sportive and mouse lemurs were not related to the forest structure variables we documented, but they did negatively predict each other—perhaps because their habitat requirements differ. These results also underscore the importance of the national park to protecting the black lemur population on Nosy Be and raise questions about what factors do influence the distribution of Nosy Be's smaller lemurs. Close monitoring is needed to prevent these populations and the ecosystem services they provide from disappearing, as have other island lemurs.

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

“…Because of various types of human activities, habitats were partially degraded and, as a consequence, the vegetation structure varied between sites and even between transects within a given site, although causal relationships cannot be evaluated in detail within this study. However, human activities such as wood extraction may explain, for example, the rather limited tree cover for large trees with DBH > 10 cm (D1, mean: 43.3%) and the regular occurrence of canopy gaps (mean = 18.0%), which indicates a higher disturbance of the canopy than in the primary and secondary forest parts of the Lokobe National Park (Nosy Bé), another site of lowland rainforest on Madagascar (Tinsman et al, 2022). Conversely, the M. gerpi sites showed relatively high densities of small‐ and medium‐sized trees, which may not yet be extensively used for wood extraction.…”

“…Twenty further fragments ranged between 1.0 and 10.0 km 2 in size, while most fragments (n = 6324) were even smaller (Figure 5). ( Tinsman et al, 2022). Conversely, the M. gerpi sites showed relatively high densities of small-and medium-sized trees, which…”