Sanford's brown lemur (Eulemur sanfordi), or Sanford's lemur is a species of strepsirrhine primate in the family Lemuridae. Sanford's brown lemur was previously considered a subspecies of the common brown lemur (Eulemur fulvus) but was raised to full species in 2001. It is named after Leonard Cutler Sanford, a trustee of the American Museum of Natural History.
This species is found at the very northernmost tip of Madagascar, ranging from Antsiranana to Ampanakana. Their populations are concentrated in a few forests – Ankarana, Analamerana and Montagne d'Ambre, with a small disjunct population in the Daraina region. The Manambato river is the southern limit of its range, although hybrids of the Sanford's brown lemur and white-fronted brown lemur appear to occur between Vohemar and Sambava. This species occurs in tropical moist, dry lowland and montane forests up to elevations of 1,400 m.
In Ankarana it appears to favor secondary forest and is active at both day and night. Sanford's brown lemur is said to display a cathemeral activity pattern, becoming most active in the afternoon and evening with occasional bouts at night.
Sanford's brown lemur is reported to associate with the crowned lemur during the wet season, a time of greater food availability. This friendly behavior would explain the occasional reports of hybrids between the two species.
Sanford's brown lemur troop sizes range from 3 to 15 individuals, numbers varying depending on location. Each troop defends a territory of up to 14 hectares, and will chase off intruding groups with territory calls rather than defending home ranges violently
