The sexes are colored differently. In S. maculatus the adult males, unless completely white, are gray spotted with white above and white below. The females are uniformly gray and usually unspotted. The young go through a sequence of color changes. The fur is dense and woolly, the snout is short, and the ears are almost invisible.
Females have four mammae.
It does not use a den or nest but is reputed to build a small sleeping platform of leaves. It is mainly nocturnal and arboreal, climbs slowly and deliberately, maintains a strong grip with its feet, and bounds at the speed of a fast human walk when on the ground. Under natural conditions it has been observed to eat fruit, flowers, and leaves, but captives have readily taken dog food and chickens. Males are aggressive and cannot be housed together in captivity. There apparently is an extended breeding season in both New Guinea and Australia.