Field studies of P. edwardsi have been carried out at Ranomafana National Park (Wright et al., 1987, 1997; Wright, 1995, 1998; Hemingway, 1995, 1996). There it is found in primary and secondary forests at middle to high elevations (600–1,600 m). The typical group size is 3–9, and groups range over areas of 100–250 ha. Population density estimates are relatively low at 8 individuals/km2. There are healthy populations south of Ranomafana National Park as well, but densities are also very low.
Infants typically are born in June and July. They transfer from their mother’s belly to her back after about three to four weeks, and ride comfortably there at about two months of age. Infant mortality has been calculated at almost 50% before the age of one year. Predation, especially by the fossa (Cryptoprocta ferox), is a significant cause of mortality, but some infant losses are also attributable to infanticide by unrelated male sifakas.
The diet consists mostly of leaves, fruit, seeds, and flowers, with approximately a dozen different plant species being sampled each day. However, dietary composition appears to vary significantly, not only from month to month but also from year to year (Hemingway, 1995, 1996).