Abstract :
[en] Tropical forests are home to the widest variety of organisms, currently estimated at around 50% of all species on the planet. They also provide important ecosystemic services, particularly in terms of global climate regulation, storage of vast amounts of carbon and oxygen production. Unfortunately, they are also extremely threatened by increased anthropogenic pressure, both direct and indirect. Indeed, deforestation and habitat fragmentation are considered to be the main threats to biodiversity today. Madagascar, one of the world’s main “hotspots” of biodiversity, has not been spared; about 90% of the island’s forest cover has disappeared and the current deforestation rates remain very high. The Island, a world priority in terms of conservation material, is notably home to an endemic group of primates, lemurs, who are completely linked to their forest habitat and for whom the state of conservation is particularly alarming.
This research project focuses on the impact of forest fragmentation on a strictly tree-dwelling species of primate in Madagascar. The study model, Lepilemur mittermeieri, is a small, little-known, folivorous and nocturnal primate, who is threatened with extinction (IUCN, 2012) and is restricted to the Ampasindava peninsula, north-west of Madagascar. This lepilemur is completely dependent on the forests of the peninsula, whose area is continuously shrinking under anthropogenic pressure. L. mittermeieri can be considered the archetype of a tree-dwelling species of primate with small distribution areas and whose habitat is threatened. The general objective of this research is to explore the ecology of L. mittermeieri and the conservation issues related to its preservation. This work is based on three specific objectives: one, to collect the first data on this species; two, to understand habitat use by L. mittermeieri; and three, to examine the future of the species in a fragmented forest environment. This work is therefore carried out on two scales, that of the individual and that of the distribution area, the Ampasindava peninsula.
At the individual scale, we studied the species ecology by focusing on the range and sleeping sites features, as well as the diet of the species and the social structure. By radio-tracking, we were able to follow about twenty individuals and highlight that the average range of L. mittermeieri is around 2 ha. We identified, on average, 4.7 sleeping sites per individual, mostly clusters of vegetation, always occupied by a single individual and almost never shared over time. Sleeping sites are mainly located in the core area of the home range. L. mittermeieri diet is diverse, with a minimum of 77 vegetable species, some of which are more commonly consumed. The species seems rather solitary, but not especially territorial as ranges overlap, even between males.
At the scale of the Ampasindava peninsula, this study shows that L. mittermeieri is found in fragments of different size, altitude and forest type. We found a density of 1.4 individuals/ha, which could represent a total population of some 10.000 individuals if the hypothesis of homogeneity within different forest fragments is confirmed. This first estimate must be taken with precaution. We also calculated an increasing rate of deforestation on the peninsula, reaching 3.14%/year between 2000 and 2014. This is confirmed by a significant reduction in the number of forest core areas and increasing fragmentation. L. mittermeieri is present in narrow forest strips indicating that the species still has the resources to survive. There is no obvious indication that the long-term survival of the species is assured.
To conclude, this work highlights the extent and speed of deforestation and fragmentation of forest habitats on the Ampasindava peninsula. The recent development of a rare earth mining project is increasing the pressure on biodiversity in this region. This work emphasizes the importance and the urgency of implementing an action plan for the conservation of L. mittermeieri.
