Rainforest sifakas occupy home ranges of 30 to 80 ha. At Mantadia, two P. diadema groups used home ranges of 33 and 42 ha (Powzyk, 1997), while P. edwardsi at Talatakely have similar-sized home ranges (~ 38 ha; Wright, 1995; Powzyk, 1997), as do P. candidus at Marojejy (44 ha; E. Patel, personal communication). P. diadema groups in continuous forest at Tsinjoarivo occupy between 70 and 80 ha but groups in fragments occupy 20-37 ha (Irwin, 2006).
In contrast, sifakas in the drier forests of the north have smaller home ranges, similar to those of western sifakas (Jolly, 1966; Richard et al., 1991). Meyers (1993) reports home ranges for P. tattersalli at Daraina between 4.4 and 12.3 ha, and P. perrieri home ranges at Analamera during the short study of Lehman and Mayor (2004) were even smaller: 1 to 1.1 ha. It thus appears that local ecology determines home range size more than phylogeny: three "diadema group" sifakas in humid forests have large ranges, while two taxa in drier forests (one "diadema group," one P. tattersalli) have small ranges. Why drier forests sustain higher sifaka densities is not entirely clear, but it has been suggested that food quality is a key issue (e.g., Powzyk, 1997). Drier forests in western and northern Madagascar have higher leaf "quality" (measured as the ratio of extractable protein to acid detergent fiber; Ganzhorn, 1992). This difference (surprisingly) may outweigh the cost of food shortages during the protracted dry season.
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