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.
