Both squirrels are highly mobile, agile climbers, with the ability to jump rapidly and surely within the tree canopy or onto the ground. Grey Squirrels can run rapidly and speeds of up to 28 km / hour across open ground have been recorded (Layne & Benton 1954). They are also an accomplished swimmers (Barkalow & Shorten 1973).
Feeding and Digestive System
Both species are essentially herbivores, but their diet includes some animal material. In its native North American forests and in Great Britain, the Grey Squirrel feeds predominantly on acorns and nuts, particularly hickory nuts, as well as pecan, walnut, hazel and beech, among others. In spring, buds and flowers, especially pollen-rich male flowers of hardwoods, are eaten. Berries, fungi and bark are included in the diet and browse may be taken when food is scarce (Barkalow & Shorten 1973). In Great Britain, apparently in the search for sweet sap (Kenward 1984), these squirrels strip the bark of trees, particularly in plantations of beech and sycamore, and can cause considerable damage. Their numbers are controlled by shooting or poisoning.
Insect larvae and pupae are eaten when available, but not in large quantities. Madson (1964) reported that as much as 4% of their diet may consist of such material. Squirrels sometimes take eggs, nestlings, frogs and lizards and may obtain minerals and some vitamins by eating soil. Because Vitamin D forms on the fur in sunlight they ingest it during grooming (Barkalow & Shorten 1973). In Melbourne and Ballarat Grey Squirrels were fed cereals, especially maize, but obtained nuts, acorns, soft fruits (especially Moreton Bay Fig), seeds and berries as well as kitchen refuse from suburban parks and gardens. They drink water although some is obtained from their food.
The Grey Squirrel feeds in the tree canopy, frequently hanging head-down amongst the branches and holding food with its forepaws. When feeding at ground level, it may use a stump or log as a feeding table. Animals of this species eat about 90 g (fresh weight) of food per day (Madson 1964) and coprophagy has been observed. A digestive tract about 2.2 m long (Barkalow & Shorten 1973) and a relatively large caecum (90 mm), are well suited to this process (Barkalow & Shorten 1973).
As Grey Squirrels cannot hibernate they store food for the severe Northern Hemisphere winter by burying single nuts or acorns in the soil, from which they are retrieved when needed. The species is very efficient at finding buried food by scent. At Ballarat, Grey Squirrels regularly cached food (the process is instinctive), but population numbers were never sufficient for all such caches to be relocated.
Palm Squirrels eat seeds throughout the year, leaves and soft fruits during autumn, and insects, particularly locusts, during summer and do not cache food. Near human settlements, they feed extensively on kitchen refuse. In Perth, Sedgwick (1968) reported that they fed on refuse and food scraps (especially bread). Wright (1972) observed them in the Perth Zoo grounds feeding on the following: fruits of Phoenix, Ficus, Morus and Melia; seeds of Brachychiton; cones of Araucaria and Pinus; buds, grass, insects and animal food. Scanlan et al. (1978) reported that Palm Squirrels eat fruit, leaves and food scraps.
The dental formula for both species is I 1/1 C 0/0 PM 2/1 M 3/3. The incisors grow continuously and are maintained chisel-sharp, whereas the molars are rooted and have prominent ridges and cusps. PM1 is a simple, peg-like tooth, but PM2 is molariform.