This is the best-studied of the three Hapalemur griseus subspecies. Home range size has been estimated to be as much as 15 to 20 ha at Ranomafana (Wright, 1989; Overdorff et al., 1999; Tan, 1999). Group size varies from two to seven, and groups can contain more than one breeding female (Pollock, 1986b; Tan, 1999). Territories are defended by scent-marking, vocal displays, and chasing. Both males and females are reported to disperse from their natal groups. Bamboo constitutes at least three-quarters of the diet, primarily new shoots and leaf bases to which these lemurs gain access by pulling new leaves from the end of a branch, biting the soft base, and discarding the tough leaf blade. Other food items include fig leaves, grass stems, young leaves, small fruits, flowers, and fungi (Wright, 1986; Overdorff et al., 1997; Tan, 1999). The birth season is essentially October–January, following a gestation of 137–140 days (Petter and Peyriéras, 1970a; Pollock, 1986b; Wright, 1990; Tan, 2000). Single infants are the rule, and the inter-birth interval is typically one year. Infants are first carried in the mother’s mouth, then on her back a few weeks after birth, and eventually she is able to “park” them for short periods while she forages (Tan, 2000).