DEFINITION AND GENERAL DESCRIPTION
Squirrels, family Sciuridae are represented in Australia by two introduced species, the American Grey Squirrel (Sciurus carolinensis) Gmelin 1788 and the Northern Palm Squirrel (Funambulus pennantii) Wroughton 1905.
Sciurids are distinguished from the only other family of Rodentia in Australia, the Muridae, by their external form, in particular a tail bushy to the base, and by skull differences, notably the presence of premolar teeth and a pronounced supra-orbital spine (Watts & Aslin 1981).
HISTORY OF DISCOVERY
Both species were privately introduced to Australia in the 19th Century; Grey Squirrels to Melbourne, Victoria, about 1880 (Seebeck 1984) and Palm Squirrels to Perth, Western Australia about 1898 (Jenkins 1977). Subsequently, Grey Squirrels were introduced to Ballarat, Victoria, in 1937 and Palm Squirrels to Taronga Zoo, Sydney, New South Wales, perhaps during the 1920s.
The Grey Squirrel is now apparently extinct in Australia (Seebeck 1984). Palm Squirrels are extinct in Sydney, but a flourishing feral colony based on Perth Zoo still exists. A captive colony has been established (1979) at Melbourne Zoo, Victoria. A similar colony at Adelaide Zoo has died out.
Museum specimens of Grey Squirrels (from Ballarat) are housed at the Museum of Victoria (Seebeck 1984), and of Palm Squirrels at the Western Australian Museum, the Australian Museum, the South Australian Museum and the Australian National Wildlife Collection (CSIRO).
Research on both species in Australia has mostly been limited to recording distribution and anecdotal information on habits and behaviour (Barrett 1934; Sedgwick 1968; Watts & Aslin 1981; Seebeck 1984), although one post- graduate study was carried out on Palm Squirrels (Wright 1972). Both species have been studied extensively overseas: Grey Squirrels in the United States and England (Shorten 1951; Lloyd 1962; Madson 1964; Barkalow & Shorten 1973) and Palm Squirrels in India and Pakistan (Prasad et al. 1966; Purohit, Kametkar & Prakash 1966; Prakash, Kametkar & Purohit 1968; Prakash 1975; Chaudry & Beg 1977).
Australian zoos, at times, have exhibited perhaps a dozen other species of sciurid, including species of Sciurus, Callosciurus, Ratufa, Cynomys and Marmota (Rix 1978), but none of these has ever established feral populations.
MORPHOLOGY AND PHYSIOLOGY
External Characteristics, Size and Body Wall
Both species are characteristically squirrel-like in appearance, with close, dense body fur and thick bushy tails, which Grey Squirrels can hold up and forward along the back. They have a broad, rounded head with large eyes and prominent rounded or triangular ears (Fig. 46.1).
The Grey Squirrel is dorsally a grizzled pale grey, due to the long straight guard hairs which are banded alternately grey and white. A rufous colouration suffuses the head, ears and in the axils of the forearm. There is a faint rufous mid-dorsal stripe. The belly is white, as are the feet. The tail fur is very long (at least four