Grey squirrel sciuris carolinensis
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Scotland . Ireland. Great Britain . Grey Squirrel ( Sciuris carolinensis ). An Invasive To The U.K. Physical Characteristics. The dorsal surface ranges from grizzled dark to pale grey and may have cinnamon tones The ears are pale grey to white and its tail is white to pale grey.

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Great Britain

Grey Squirrel (Sciuriscarolinensis)

An Invasive To The U.K.

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Physical Characteristics

  • The dorsal surface ranges from grizzled dark to pale grey and may have cinnamon tones

  • The ears are pale grey to white and its tail is white to pale grey.

  • Under-parts are grey to buff

  • The total length of these squirrels ranges from 380 to 525 mm

  • Tail length ranges from 150 to 250 mm

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  • Breeding occurs in December-February and May-June and is slightly delayed in more northern latitudes.

  • Gestation lasts 44 days.

  • Most females begin their reproductive life at 1.25 years but can bear young as early as 5.5 months.

  • Females may bear young twice a year for more than 8 years.

Grey Squirrels Competing to Mate

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Litter Size

  • Newborns are naked

  • They weigh from 13-18g

  • Generally 2-4 young per litter (up to 8 young are possible)

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Life Span/Longevity

  • The maximum longevity is 12.5 years in the wild

  • However, a captive female lived to be over 20 years of age.

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Grey Squirrel Drey

Drey: The proper name for a squirrel nest.

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Native Habitat

  • The deciduous forests of North America.

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Deciduous Forest

  • Deciduous: shedding of the leaves annually.

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Introduction to the U.K.

  • The North American grey squirrel was deliberately introduced to Britain and other parts of Europe during the 19th Century.

  • Was released merely as a curiosity to satisfy the Victorian penchant for novelty.

  • Since then the adaptable and hardy grey squirrel has thrived in Britain’s parks, gardens and woodlands.

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2008 Grey & Red Estimates

  • 5 million estimated number of grey squirrels in the UK.

  • 120,000 estimated number of red squirrels in the U.K.

Red Dots= Current Red Squirrel Distribution

Black Dots= Current Grey Squirrel Distribution

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Grey Squirrel vs. Red Squirrel

  • The grey squirrel is able to out-compete the red in almost every phase of their life history.

  • It is also thought that the grey squirrel is more resistant to disease than the red .

  • The grey squirrel has now spread to occupy almost all of England with only the far north and a few more southerly areas as yet unoccupied

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Grey Squirrel vs. Red Squirrel

  • Grey squirrels can weigh as much as 600 grams, twice that of an adult red squirrel.

  • Grey Squirrels live for an average of 7-9 years, compared to 6-8 years for reds.

  • They therefore have a significant physical advantage over the red squirrel.

  • In addition, having evolved in the oak and hickory forests of the north-eastern United States, grey squirrels also have several behavioral advantages over reds.

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Grey Squirrel vs. Red Squirrel

  • The red squirrel, which is primarily arboreal and spends only 33% of its time on the ground.

  • The grey squirrel spends up to 80% of its time foraging on the woodland floor.

  • This adaptation means that, in the autumn, grey squirrels can increase their body weight by as much as 20% while reds, which feed far less efficiently in broadleaved woodland, rarely manage to gain 10%

Poor Little Red Squirrel

Big, Bad Grey Squirrel

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Grey Squirrel vs. Red Squirrel

  • Neither grey nor red squirrels hibernate.

  • Both are therefore active throughout the winter months periods of extreme weather.

  • However, when they are forced spend several days in the drey without feeding, can have severe consequences for the red squirrel, which cannot store as much fat as the grey.

  • This deficiency is reflected in the fact that only 80% of young red squirrels survive their first winter and mortality remains as high as 50% in adults

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Disease Between Species

  • In 1984 in East Anglia, a squirrel was found to be infected with a disease that was identified as a parapoxvirus.

  • This disease is fatal to red squirrels, but it is carried by the grey squirrel.

Parapox Virus

Red Squirrel with Parapox Virus

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Economic Impact of Grey Squirrel

  • Grey squirrels, can cause significant damage to trees such as sycamore, beech, oak, sweet chestnut, pine, Norway spruce and larch, by bark-stripping.

  • This activity results in the death of only 5% of trees.

  • In 2000 it was estimated that squirrel damage reduced the value of commercially grown trees in the UK by £10 million (This is $20 million U.S. dollars.)

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Some Economic Examples

Wind-snap to 40-year old Norway spruce following grey squirrel bark-stripping damage

Grey squirrel bark-stripping to main stem of sycamore

Grey squirrel damage to 18-year old planted oak

Fresh grey squirrel basal damage to beech

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Ecological Impact

  • Grey squirrels may be partly responsible for recent declines in many woodland bird species.

  • They can exert this impact either through the predation of eggs and young chicks

  • They also take over nest sites and consume food such as seeds and nuts which would otherwise be exploited by birds.

Grey Squirrel Eating A Bird

Grey Squirrel Eating Duck Egg

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Management Practices

  • Lethal control is governed by strict legal guidelines, but permission can be obtained to shoot, trap or poison grey squirrels to achieve the goals described previously.

  • The Forestry Commission currently spends £200,000 (This is $400,00 in U.S. dollars) per year controlling red squirrels, but they estimate that a great deal more would have to be spent for all of their serious impacts on British wildlife to be reversed.

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Or You Could Get Yourself a Scotsman

  • “Armed with traps and air rifles, a team of nine squirrel protection officers will set to work in the Borders, supported, they hope, by members of the public.”

  • “Their aim will be to kill every grey squirrel in the south of Scotland within two years, to stop the animals spreading further north.”

    ~ The Scotsman Magazine~

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So… Let’s Think About This!?!

  • Nine of Scotland’s elite officers will kill ALL five million squirrels within Two years.

  • So that would then mean that each individual man would have to kill and average of 762 squirrels per day, everyday for the next two years with no days off.

  • This can only happen however, if there is absolutely no reproduction

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  • Now, for an average person, this kind of job would be not only be physically exhausting, but mentally & emotionally as well.

  • But to a Scotsman this is just kiddy stuff.

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“I never saw one walk -- and then suddenly, before you could say Jack Robinson, he would be in the top of a young pitch pine, winding up his clock and chiding all imaginary spectators, soliloquizing and talking to all the universe at the same time...”

~Henry David Throreau~

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The Tale of Squirrel Nutkin could say Jack Robinson, he would be in the top of a young pitch pine, winding up his clock and chiding all imaginary spectators, soliloquizing and talking to all the universe at the same time...”

“This is a Tale about a tail--a tail that belonged to a little red squirrel, and his name was Nutkin.” ~Beatrix Potter~