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NATURE'S BLUEPRINT

The indigenous Douglas and pine tree squirrels are incredible and an integral part of the web of life within coastal and interior forests of British Columbia.

Douglas squirrels are only found on the south-coast whereas pine squirrels live throughout the rest of the province. They are easily recognizable compared to the introduced eastern gray squirrels or black fox squirrels. Native British Columbia squirrels have deep reddish or chestnut coloration with white-eye rings. They are considerably smaller in size than the introduced squirrels and so the indigenous squirrels have lost some of their habitat.

Tree squirrels, as their name implies, spend a good deal of time in forest treetops. They have powerful limbs, elongated digits and sharp recurved claws. They also have flexible ankles with hind-feet that are able to rotate 180 degrees enabling them to scamper down trees head first. Ever growing front teeth, molars and powerful jaws are critical assets since their main food source is the seeds inside conifer cones.

The most distinguishing feature of a tree squirrel is its tail, which accounts for about 40 per cent of body length. Not only does the tail aid in balance when performing spectacular acrobatics, but it also assists in regulating heat loss or gain (thermoregulation). Bundles of blood vessels at the base of the tail help retain heat in the body core or dissipate it more readily.  In addition, the tail is used for communicating; its orientation and movement convey information to other squirrels and predators. It also acts as the perfect parasol protecting against sun or rain.

Male and female tree squirrels are indistinguishable from a distance. They are the same size and their thick fur is light colored on the underside and relatively dark on the upper side. The dark color provides excellent camouflage from predators above while their pale underside enables them to blend against the light colored sky.

Tree squirrels are daytime (or diurnal) creatures with magnificent eyes that are able to differentiate certain colors like reds and greens. Their black whiskers are important tactile sensory organs and their superior intelligence is ascribed to their relatively large brain.

They rely heavily, but not exclusively, on tree seed as food.  In certain years, conifers produce an abundance of cones, tree scientists call this a mast crop. Unfortunately for tree squirrels, mast crops do not occur every year, hence it’s either feast or famine and population numbers fluctuate wildly according to availability of food. This presents an energy problem for an active critter whose heart beats between 150 and 450 beats per minute and does not hibernate during the winter.

So how do tree squirrels survive winter? They are prodigious workers and hoarders of food. They harvest whole conifer cones and store them in caches (called middens) that are underground, in hollow stumps or hollowed fallen logs. They must keep the cones moist to prevent them from drying out and shedding seeds. The squirrels have even been known to store cones in streams or springs where seed remains fresh for a year or more.

After awakening from hibernation both black and grizzly bears can often be seen raiding middens in search of any remaining protein-rich tree seeds.

Not all the seeds in caches are eaten. Some germinate and eventually become mature trees.

During the spring and summer, tree squirrels will eat a variety of foods from truffles to tree bark, tree buds, sap, insects, eggs and even mice.  Goshawks, owls, martens, fishers and bobcats prey on tree squirrels.

Perhaps most significant, the presence of native tree squirrels is a barometer of a forested ecosystem’s health, especially after a disturbance such as fire or insect infestations.

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Earth Dr Reese Halter is an award-winning broadcaster and distinguished biologist. His latest books are The Insatiable Bark Beetle and The Incomparable Honeybee

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Text © by Dr Reese Halter 2012. All rights reserved.

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