40-50 m for females; in Perth the range was 50–135 m, that of males averaging about 90 metres. The species is not territorial, although the animals may defend nest and roost sites. Dominant males, may however, kill persistent intruders. During reproductive activity, females are thought to initiate courtship.
Predation in the wild is apparently low (varanid lizards are reported predators). In Australia, introduced mammalian predators do not seem to be a major problem, but corvids and diurnal raptors harass squirrels (Scanlan et al. 1978). Wright (1972) reported predation of Palm Squirrels by captive hawks and brolgas at the Zoo and by rats, cats and Nankeen Night-herons. Perhaps the greatest predation was by humans; active population culling by Zoo staff is used to limit populations and there may be some mortality during and consequent upon annual pruning of palm trees. Road casualties are another human-based cause of mortality.
No specific diseases have been reported for the species. In India, several nematode parasites have been reported (Johnson 1975) and in Australia, megostigmatid mites (Ornithonyssus bacoti) were present on some squirrels (Agriculture Protection Board of Western Australia, personal communication 1986). Wright (1972) found a coccidiosid, possibly Eimeria sciuri, in the gut of two specimens examined.
The native habitat of the Grey Squirrel is dense hardwood forests, particularly those of oak, hickory and walnut, but in Australia it was found only in suburban parks and gardens (Seebeck 1984). It never became established in natural forest and healthy populations seemed to depend on being fed by humans. In North America, the species encounters some competition from the Fox Squirrel (Sciurus niger) and in the United Kingdom, the Grey Squirrel has been implicated with a dramatic reduction in range of the European Red Squirrel (Sciurus vulgaris). Recent work suggests that it is effective in preventing recolonisation by the latter species (Tittensor 1977).
The flea Orchopeas howardi, is specific to the Grey Squirrel with which it was introduced to England, but is not recorded from Australia, although other fleas, mites and lice have been reported. Viruses (foot and mouth disease, leptospirosis, mange), coccidiosis and shock disease are reported for Grey Squirrels (Tittensor 1977).
Predation in the wild, especially on young animals, is widespread and many natural predators are implicated. In Australia, dogs, cats and humans were important predators (Seebeck 1984). Reported overlapping home ranges varied from 1–20 ha, with male ranges greater than those of females. Population densities range between one and 13 squirrels ha-1 and often depend on food abundance. At Ballarat, the maximum population was estimated as about 100, a density of about 1 ha-1. Mass migrations have been recorded in North America, but not in other populations – these are thought to be the result of food crop failure.
Feeding behaviour, courtship and reproductive behaviour are described above. Feeding and other activities are generally not observed until several hours after sunrise and there is a peak in activity 1–2 hours before sunset (Wright 1972). Basking is a usual precursor to morning activity and as shade increased in late afternoon, the animals tend to be quiet. Palm Squirrels avoid heat stress by sheltering in canopy vegetation and limit foraging activity when ambient temperatures are high (Ghosh 1975). Squirrels are tolerant of each other when feeding, often forming large groups. Scanlan et al. (1978) observed much chasing upon encounter, accompanied by chattering. Squirrels at Como High School, Perth, tended to seek shelter when students were out of class and be active in the open during class hours.