Reddish Vale Country Park
Native to the eastern and midwestern United States, and to the southerly portions of the eastern provinces of Canada, the grey squirrel was intoduced to Britain at the begining of the 20th century,
Gray squirrels are scatter-hoarders; they hoard food in numerous small caches for later recovery. Some caches are quite temporary, especially those made near the site of a sudden abundance of food which can be retrieved within hours or days for re-burial in a more secure site. Others are more permanent and are not retrieved until months later. It has been estimated that each squirrel makes several thousand caches each season. The squirrels have very accurate spatial memory for the locations of these caches, and use distant and nearby landmarks to retrieve them. Smell is used once the squirrel is within a few centimeters of the cache. It is one of very few mammalian species that can descend a tree head-first. It does this by turning its feet so that the claws of its hindpaws are backward pointing and can grip the tree bark.
Gray squirrels build a type of nest, known as a drey, in the forks of trees. The drey consists mainly of dry leaves and twigs. Squirrels may also nest in the loft or exterior walls of a house. In addition, the squirrel may inhabit a permanent tree den.
Gray squirrels are more active during the early and late hours of the day, and tend to avoid the heat in the middle of a summer day. They do not hibernate.
Predators include humans, hawks, cats, owls and dogs. Whilst gray squirrels fight among themselves over food sources, they have been known to mob potential predators such as domestic cats. They also have a complex, tag-team defensive system involving distracting would-be predators with vigorous shaking of their tails.
Grey squirrels spread rapidly across England and then became established in both Wales and parts of southern Scotland. On mainland Britain, it has almost entirely displaced the populations of native red squirrels.
In the United Kingdom, the gray squirrel has few natural predators. This has aided its rapid population growth and has led to the species being classed as a pest. Measures are being devised to reduce its numbers, including one plan for celebrity television chefs to promote the idea of eating the squirrels. In areas where relict populations of red squirrel survive, such as Anglesey and Brownsea, programs seeking to eradicate pest squirrels are in progress in an effort to allow red squirrel populations to recover.
Although complex and controversial, the main factor in the gray squirrel's displacement of the red squirrel is thought to be its greater fitness and, hence, a competitive advantage over the red squirrel on all measures. The gray squirrel tends to be larger and stronger than the red squirrel and has been shown to have a greater ability to store fat for winter. The squirrel can therefore compete more effectively for a larger share of the available food, resulting in relatively lower survival and breeding rates among the red squirrel. Parapox virus may also be a strongly contributing factor; red squirrels are fatally affected by the disease, while the gray squirrels are unaffected but thought to be carriers. The red squirrel is also less tolerant of habitat destruction and fragmentation which has led to its population decline, while the more adaptable grey squirrel has taken advantage and expanded.
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