Edge effects are caused by the penetration of abiotic and biotic conditions from the matrix into forest interiors. Although edge effects influence the biogeography of many tropical organisms, they have not been studied directly in primates. Edge effects are particularly relevant to lemurs due to the loss of 80-90% of forests in Madagascar. In this study, data are presented on how biotic edge effects influenced the distribution and density of lemurs in the Vohibola III Classified Forest in southeastern Madagascar. In total, 415 lemur surveys were conducted during June-October 2003 and May-September 2004 along six 1,250-m transects that ran perpendicular to the forest edge. Data were also collected on lemur food trees along the six transects (density, height, diameter at breast height, area, volume, and distance to forest edge). Four nocturnal species (Avahi laniger, Cheirogaleus major, Lepilemur microdon, and Microcebus rufus) and four diurnal species (Eulemur rubriventer, Eulemur fulvus rufus, Hapalemur grisesus griseus, and Propithecus diadema edwardsi) were sighted during surveys. Regression analyses of lemur densities as a function of distance to forest edge provided edge tolerances for A. laniger (edge-tolerant), M. rufus (edge-tolerant), E. rubriventer (edge-tolerant or omnipresent), and H. g. griseus (omnipresent). The density and distribution of M. rufus and their foods trees were correlated. Edge-related variations in food quality and predation pressures may also be influencing lemurs in Vohibola III. Tolerance for edge effects may explain, in part, how lemurs have survived extreme habitat loss and forest fragmentation in southeastern Madagascar.

Forest edges are dynamic zones characterized by the penetration (to varying depths and intensities) of conditions from the surrounding environment (matrix) into the forest interior. Although edge effects influence many tropical organisms, they have not been studied directly in primates. Edge effects are particularly relevant to lemurs because of the highly fragmented forest landscapes found in Madagascar. In this study, data are presented regarding how the densities of six lemur species (Avahi laniger, Cheirogaleus major, Eulemur rubriventer, Hapalemur griseus griseus, Microcebus rufus, and Propithecus diadema edwardsi) varied between six 500-m interior transects and six 500-m edge transects in the Vohibola III Classified Forest in SE Madagascar. Diurnal (n = 433) and nocturnal (n = 128) lemur surveys were conducted during June-October 2003 and May-November 2004. A. laniger, E. rubriventer, and H. g. griseus exhibited a neutral edge response (no differences in densities between habitats). M. rufus and P. d. edwardsi had a positive edge response (higher densities in edge habitats), which may be related to edge-related variations in food abundance and quality. Positive edge responses by M. rufus and P. d. edwardsi may ultimately be detrimental due to edge-related anthropogenic factors (e.g., hunting by local people). The negative edge response exhibited by C. major (lower densities in edge habitats) may result from heightened ambient temperatures that inhibit torpor in edge habitats.

Greater bamboo lemurs (Prolemur simus) are endemic to Madagascar and are the only recognized species within their genus. The IUCN lists the species as critically endangered, with very few confirmed distribution records and <200 individuals known in the wild. With the aim of contributing to its conservation, we attempted to find previously unknown sites containing the species. Working closely with local communities, and basing our methodology on the gathering of local knowledge, we surveyed 44 sites in and around the Ankeniheny-Zahamena Corridor.We found evidence of the presence of Prolemur simus at 18 sites. We made direct sightings at 6 sites, of a total of 65 confirmed individuals, and identified their characteristic feeding remains at the other sites. Twelve of the sites are located in midaltitude rain forest within the corridor, and 6 lie in isolated and degraded lowland areas outside the corridor. These discoveries more than double the number of sites where the species is known to occur, and extend its known range 85 km further north. We identified numerous threats to the newly discovered sites, including hunting pressure, habitat destruction, habitat disturbance, and habitat fragmentation. Demographic factors related to small population sizes and population isolation may also impact the viability of the populations. Our results illustrate the benefits of systematic gathering of local knowledge when searching for rare or secretive primates.

We investigated how greater dwarf lemur (Cheirogaleus major) densities, ambient air temperature, and dendrometrics (tree height and diameter) varied along forest edge-interior gradients in the Vohibola

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This paper describes the results of field surveys for two Endangered lemurs, Milne-Edward's sifaka Propithecus diadema edwardsi and the black and white ruffed lemur Varecia variegata variegata, in the unprotected Fandriana-Marolambo forest corridor in south-east Madagascar. Published range maps show P. d. edwardsi and V. v. variegata present in the corridor, although few surveys have been conducted in this area.A total of 292.9 km of surveys were conducted at eight sites in the corridor but P. d. edwardsi and V. v. variegata were each located at only one site. Absence of these species at other sites may be the combined result of altitudinal and anthropogenic effects. Conservation plans for P. d. edwardsi and V. v. variegata are complicated because gaps in forest cover prevent dispersal of conspecifics from nearby protected areas. Conservation authorities should be cautious in using range maps based on the presumed distribution of lemur species.

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To improve our knowledge of the distribution of the critically endangered greater bamboo lemur Prolemur simus, we surveyed 6 sites in eastern Madagascar. We found its characteristic feeding signs at 5 sites and made a direct sighting at one of these. One site represents a northern extension of 45 km of the known extant range of the species. Two sites are located in a forest corridor approximately halfway between the previously known southern and northern populations, therefore suggesting a broadly continuous distribution of the species within its range rather than the previously suspected distribution of two distinct populations separated by a distance of over 200 km. Our results illustrate the benefit of species-focussed surveys in determining the true distribution of endangered species, a realistic measure which is necessary in order to assess their current status and to prioritise long-term conservation interventions.