Line-transect surveys were conducted at a small remnant of semideciduous Atlantic Forest to estimate primate density and population size. The Mata São José has about 230 ha and it is located between Rio Claro and Araras (São Paulo State, southeastern Brazil). This forest fragment holds 23 non-volant mammal species distributed in seven orders e 13 families. From July 1999 to January 2001, a total of 125 km were walked and three primate species were recorded. The densities were estimated based on Distance software. Brown capuchin monkey Cebus nigritus (Goldfuss, 1809) (Cebidae) presented the highest population density (24.5 individuals/ km², ranging between 19.6 and 32.6 individuals/ km²). Titi monkeys Callicebus nigrifrons (Spix, 1823) (Pitheciidae) and tufted ear marmosets Callithrix aurita (É. Geoffroy, 1812) (Callitrichidae) presented 3.5 individuals/ km² (ranging between 2.8 to 4.6 individuals/ km²). Total population size of brown capuchin monkeys was 56 individuals (ranging between 45 to 75 individuals) and the titi monkeys and tufted ear marmosets were eight individuals (ranging between six to 10 individuals). Titi monkeys and tufted ear marmosets are vulnerable to extinction and both persist at Mata São José, but at low population densities. These primate species are at local extinction risk, because populations at low densities are more suscetible to stochastic events, inbreeding depression and environmental variation. Translocation is the only plausible management action that could avoid local extinction of these primates.
Atlantic forest; census; forest fragmentation; line-transect method; primates
