Grey Squirrel
The Grey Squirrel is a tree squirrel native to eastern North America where it is known as the Eastern Gray Squirrel. In Europe, where it is known as the Grey Squirrel, it is regarded as an invasive species.
The head and body length of the Grey Squirrel ranges from 9 to 12 inches with a tail of 7.5 to 10 inches. It has predominantly grey fur with a white underside and it has a large bushy tail. Males and females are similar in size and colouration.
The Grey Squirrel can be found in east and mid-west USA and the south of the eastern provinces of Canada. It was introduced to Vancouver Island in west Canada and has spread widely from there and was also introduced to and thrives in west USA. It has additionally been introduced in to the UK, Ireland, Italy, South Africa and Australia (where it was extinct by 1973).
Following its introduction to the UK from the USA in the late 19th/early 20th century, the Grey Squirrel spread rapidly across England and then became established in both Wales and parts of southern Scotland. On mainland UK, it has almost entirely displaced the populations of the native Red Squirrel. In the UK, the Grey Squirrel is not regulated by natural predators, other than the Pine Marten, which is generally absent from England and Wales. 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. In areas where relict populations of the Red Squirrel survive, such as the islands of Anglesey in Wales and Brownsea in Dorset, programmes exist to eradicate the Grey Squirrel in an effort to allow the Red Squirrel population to recover.
The main factor in the Grey Squirrel's displacement of the Red Squirrel is thought to be its greater fitness, hence a competitive advantage over the Red Squirrel. The Grey 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. It 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. Parapoxvirus may also be a strongly contributing factor. The Red Squirrel has long been fatally affected by the disease whilst the Grey Squirrel is both unaffected but thought to be a carrier. The Red Squirrel is also less tolerant of habitat destruction and fragmentation which has led to its population decline, whilst the more adaptable Grey Squirrel has taken advantage and expanded.
The Grey Squirrel can be found inhabiting large areas of mature, dense woodland with a dense understorey vegetation. Deciduous woodland is preferred over coniferous woodland. Close to human settlements, it can be found in parks, in the gardens of houses within urban environments and in the farmlands of rural environments.
The Grey Squirrel generally prefers constructing its den or drey on large tree branches, in the fork of trees and within the hollow trunks of trees. It has also been known to take shelter within abandoned bird nests. The roughly spherical drey consists mainly of dry leaves and twigs and is usually insulated and lined with moss plants, thistledown, dried grass and feathers. Males and females may share the same drey for short periods during the breeding season and during cold winter spells.
The Grey Squirrel can breed twice a year but younger and less experienced mothers normally have a single litter per year in the spring. Depending on forage availability, older and more experienced females may breed again in the summer. The breeding seasons are December to February and May to June although this is slightly delayed in more northern latitudes. The first litter is born in February or March and the second in June or July, although this may be advanced or delayed by a few weeks depending on climate, temperature and forage availability. Normally, 1 to 4 young are born in each litter but the largest possible litter size is 8. The gestation period is about 44 days and the young are weaned after around 10 weeks. The young begin to leave the nest after 12 weeks with autumn born young often wintering with their mother. Only 1 in 4 squirrel kits survives to 1 year of age with mortality around 55% for the following year. Mortality rates then decrease to around 30% for the following years until they increase sharply at 8 years of age.
The Grey Squirrel can live to be 20 years old in captivity but in the wild live much shorter lives due to predation and the challenges of their habitat. At birth its life expectancy is 1 to 2 years, an adult typically can live to be 6 years old and exceptional individuals can make it to 12 years old.
The Grey Squirrel eats a wide range of foods such as tree bark, tree buds, berries, many types of seeds and nuts and some types of fungi. It can cause damage to trees by tearing the bark and eating the soft tissue underneath. The Grey Squirrel also has a high enough tolerance for humans to inhabit residential neighbourhoods and raid bird feeders for seeds and nuts and gardens for fruit and other garden crops. On very rare occasions, when its usual food sources are scarce the Grey Squirrel will also prey on insects, frogs, small rodents including other squirrels and small birds, their eggs and young.
Date: 5th June 2023
Location: NWT Weeting Heath, Norfolk
The head and body length of the Grey Squirrel ranges from 9 to 12 inches with a tail of 7.5 to 10 inches. It has predominantly grey fur with a white underside and it has a large bushy tail. Males and females are similar in size and colouration.
The Grey Squirrel can be found in east and mid-west USA and the south of the eastern provinces of Canada. It was introduced to Vancouver Island in west Canada and has spread widely from there and was also introduced to and thrives in west USA. It has additionally been introduced in to the UK, Ireland, Italy, South Africa and Australia (where it was extinct by 1973).
Following its introduction to the UK from the USA in the late 19th/early 20th century, the Grey Squirrel spread rapidly across England and then became established in both Wales and parts of southern Scotland. On mainland UK, it has almost entirely displaced the populations of the native Red Squirrel. In the UK, the Grey Squirrel is not regulated by natural predators, other than the Pine Marten, which is generally absent from England and Wales. 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. In areas where relict populations of the Red Squirrel survive, such as the islands of Anglesey in Wales and Brownsea in Dorset, programmes exist to eradicate the Grey Squirrel in an effort to allow the Red Squirrel population to recover.
The main factor in the Grey Squirrel's displacement of the Red Squirrel is thought to be its greater fitness, hence a competitive advantage over the Red Squirrel. The Grey 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. It 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. Parapoxvirus may also be a strongly contributing factor. The Red Squirrel has long been fatally affected by the disease whilst the Grey Squirrel is both unaffected but thought to be a carrier. The Red Squirrel is also less tolerant of habitat destruction and fragmentation which has led to its population decline, whilst the more adaptable Grey Squirrel has taken advantage and expanded.
The Grey Squirrel can be found inhabiting large areas of mature, dense woodland with a dense understorey vegetation. Deciduous woodland is preferred over coniferous woodland. Close to human settlements, it can be found in parks, in the gardens of houses within urban environments and in the farmlands of rural environments.
The Grey Squirrel generally prefers constructing its den or drey on large tree branches, in the fork of trees and within the hollow trunks of trees. It has also been known to take shelter within abandoned bird nests. The roughly spherical drey consists mainly of dry leaves and twigs and is usually insulated and lined with moss plants, thistledown, dried grass and feathers. Males and females may share the same drey for short periods during the breeding season and during cold winter spells.
The Grey Squirrel can breed twice a year but younger and less experienced mothers normally have a single litter per year in the spring. Depending on forage availability, older and more experienced females may breed again in the summer. The breeding seasons are December to February and May to June although this is slightly delayed in more northern latitudes. The first litter is born in February or March and the second in June or July, although this may be advanced or delayed by a few weeks depending on climate, temperature and forage availability. Normally, 1 to 4 young are born in each litter but the largest possible litter size is 8. The gestation period is about 44 days and the young are weaned after around 10 weeks. The young begin to leave the nest after 12 weeks with autumn born young often wintering with their mother. Only 1 in 4 squirrel kits survives to 1 year of age with mortality around 55% for the following year. Mortality rates then decrease to around 30% for the following years until they increase sharply at 8 years of age.
The Grey Squirrel can live to be 20 years old in captivity but in the wild live much shorter lives due to predation and the challenges of their habitat. At birth its life expectancy is 1 to 2 years, an adult typically can live to be 6 years old and exceptional individuals can make it to 12 years old.
The Grey Squirrel eats a wide range of foods such as tree bark, tree buds, berries, many types of seeds and nuts and some types of fungi. It can cause damage to trees by tearing the bark and eating the soft tissue underneath. The Grey Squirrel also has a high enough tolerance for humans to inhabit residential neighbourhoods and raid bird feeders for seeds and nuts and gardens for fruit and other garden crops. On very rare occasions, when its usual food sources are scarce the Grey Squirrel will also prey on insects, frogs, small rodents including other squirrels and small birds, their eggs and young.
Date: 5th June 2023
Location: NWT Weeting Heath, Norfolk
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