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 Douglas Squirrel

(Tamiasciurus douglasii)

Introduction

There are 3 native species of squirrels in BC; the Red, the Douglas and the Northern Flying Squirrel. Squirrels are broadly divided into 3 categories: tree, ground and flying squirrels. The subject of this article, the Douglas squirrel, is a tree squirrel. Found exclusively on the Pacific Coast, the Douglas Squirrel is a quick, agile, playful little creature that we frequently see around our lake. This  squirrel is often heard before it is seen; producing a lot of  noise for its small size. It can chatter, squeak,  scold and emit a “chirp” that might make you think you are hearing a bird.

 

So once you hear and see a scampering little rodent going up a tree ….are you sure it’s a squirrel? ….or could it be a chipmunk? The differences to keep in mind are that a squirrel:

   -is larger in size

    -has a bushier tail

    -and does not have a dark stripe

     with a central white stripe running

along its back and head.

 

Douglas Squirrels (and also Douglas Firs) are named for the Scottish explorer and botanist, David Douglas, who identified them in 1825 and 1826 when he tramped and canoed the Pacific Northwest with trappers from the Hudson’s Bay Company. 

 

This article features many interesting facts that you might want to know about Douglas Squirrels and their place in the ecosystems of BC’s south coast.

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Range

 

In Canada, the Douglas Squirrel is only found in BC. Native to the Pacific coast of North America, the Douglas Squirrel inhabits the coniferous forests of southwest BC, western Washington and Oregon, and northwest California and the Sierra Nevada region.

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Characteristics - Anatomy

Appearance

Douglas Squirrels (DS) have brown backs, tawny orange bellies and pale rings around their eyes. This colouring changes slightly with the seasons. In summer, a dark line down their sides that looks like a racing stripe is noticeable. In winter, their coats and markings are grayer and they grow small dark ear tufts. 

In length, adults average about 20 cm. (8 in.) of body and 13 cm (5 in.) of tail. They generally weigh between 150 (5.5 oz.) and 300 grams (10.5 oz.).  

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Senses

The DS has a keen sense of smell, hearing and eyesight. In addition, it has whiskers above and below its eyes and on its nose and chin to help in ‘sensing’ its surroundings.

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Teeth

The orange coloured front teeth of the DS never stop growing. It is estimated that their teeth grow 6 inches a year. To keep these front teeth sharp, clean and worn down, the DS is continually engaged in chewing on solid things like twigs. The necessity and the instinct to keep chewing may also be the reason you find chewed wires, hoses and siding. 

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Legs

The DS is amazing to watch as it runs up and down tree trunks and leaps among branches with such quickness and agility. This is made possible by a design that involves double jointed hind legs, strong muscles, extremely flexible ankles and very sharp claws on the four front toes and five back toes. 

Behavior

 

The Douglas Squirrel is diurnal; very active during the day and asleep at night. 

The males do not participate in raising the young and can be described as solitary with the exception of the mating season. A lone DS will establish a territory that is usually a hectare in size (100m x 100m) and will be very energetic in defence of this territory. 

Douglas Squirrels build summer nests in the ground, in structures and in trees using moss, lichen and pieces of bark and twigs.  They do not hibernate. In colder winter weather they prefer cavities in trees or holes made by woodpeckers in which to build their nest. 

The Douglas Squirrel is very vocal and territorial and has a variety of calls depending on whether it is courting, defending its territory or sounding an alarm. John Muir (1838-1914) an influential American naturalist and conservationist wrote:

“He is the mocking-bird of squirrels, pouring forth mixed chatter and song like a perennial fountain; barking like a dog, screaming like a hawk, chirping like a blackbird or a sparrow; while in bluff, audacious noisiness he is a very jay.”

Here is a short video "THE DOUGLAS SQUIRREL - A SQUIRREL WITH ATTITUDE. Vocalisation & territorial behaviour"

Life Cycle

Douglas Squirrels are thought to have a life span of 5 - 6 years.

 

Each year, in the spring, Douglas Squirrels are part of a yearly mating process that involves a noisy chase and then a monogamous bond (one mate per mating season).  After mating a gestation period of 31-35 days follows.

 

As summer approaches, many females begin construction of a nesting site weaving twigs and bark into an outer 8 inch wide spherical frame and using grass, moss and lichen as a lining. These nests, called dreys, are usually built in a stable, safe location, like the fork of a tall tree, at a height of 20-30 feet above the ground.

Females usually yield a single litter per year of 4 - 6 tiny, pink young. Occasionally, when food is plentiful, another litter is produced at the end of the breeding season, in August or September.

 

Development of the Young

At Birth:  Blind, hairless, weighing 13-18 grams (0.4 - 0.6 oz.).

18 days old: Fur starts to grow.

26-36 days old:  Eyes begin to open.

6-9 weeks old:   Weaning begins.

4-7 months old:  The young are independent but continue to stay close to the mother. 

8-9 months old:  In the spring, a year after birth, they reach sexual maturity.

DS babies.JPG

Foraging and Diet

Because the seeds of pine cones make up a major part of the its diet, the Douglas Squirrel is termed a granivore (seed and grain eater). It also eats twigs, the cambium layer of conifers, sap, leaves, buds, acorns and other nuts, mushrooms, fruits, and berries. Occasionally it will also eat insects, birds’ eggs, and nestlings.

 In the fall, Douglas Squirrels begin to prepare for the upcoming winter and at the lake we start to hear the sound of pine cones bouncing off our cabin roofs. These cones will be gathered up and buried in a damp underground place.

This underground storage area, called a midden, becomes a larder, and is the source of a large quantity of fresh and nutritious seeds and cones for eating throughout the winter.

 

From a safe eating perch, often directly above the midden, Douglas Squirrels strip the outside scales of a cone with their sharp incisor teeth and extract their conifer-seed meal.  The result is a well fed squirrel and a midden that becomes covered in a thick pile of cone scales. Quite a few tree seedlings have also sprouted thanks to uneaten seeds in forgotten middens.

The Douglas Squirrel also feeds on mushrooms and truffles, the reproductive structures of fungi. Sometimes the DS will hang these mushrooms or truffles where small tree limbs branch in order to dry and store them. Once eaten, fungal spores (which lack a dispersal system) get spread around the forest in the squirrel’s feces. Many of these fungal spores connect underground with vast symbiotic networks that nourish soil, plants and tree roots.

 

An impressive cycle of interdependence revolves around  “how predators need rodents; how rodents need fungi for food and trees for shelter; how trees need fungi for nutrients; how fungi need trees for sugars and rodents for dispersal of their spores.” fitznaturalist.com 

Predators and Threats

 

Although the Douglas Squirrel is quick and agile, can climb trees, has great peripheral vision and very sharp teeth, it nevertheless is positioned well down the food chain. DS are prey for weasels, Pacific martens, coyotes, bobcats, goshawks, foxes, owls, mink, and racoons. Humans also kill squirrels - directly when using air rifles, small calibre rifles, and slingshots - and indirectly by reducing the area of the forest habitat critical to these animals, and by introducing toxins into their environment. Humans have also been known to dig up cones from middens for selling to seed stores or tree planting outfits. This drastically diminishes the squirrel’s winter food supply and thus its chance of survival.  

Endangered or Invasive Species

The mortality rate in the first year of the DS’s life is very high. Despite this, the Douglas Squirrel can be found on the “Yellow List” of the BC Conservation Status Rankings, indicating a species that is apparently secure and not at risk of extinction. Fluctuations in population size are usually tied to the food supply. Since a very large proportion of the Douglas Squirrel’s diet consists of the seeds of pine cones, years of Douglas fir pine cone failure or low production, result in Douglas Squirrel populations declining as well.

 

Concerns and Recommendations

Tree squirrels can carry disease and host parasites (internal or external) that carry pathogens that in turn can potentially be harmful to humans. Such diseases can be transmitted through bites or other forms of direct contact with infected squirrels.

 

Small mammals such as mice and squirrels almost never have rabies. Overall, there is minimal documentation of disease transmission from tree squirrels to humans. 

However, squirrel bites are the most commonly reported animal-related injury in cottage country. This should dissuade us from any further attempts to “hand feed” these critters.

The following website (Living with Wildlife:Tree squirrels) has some practical ideas for keeping squirrels away from bird feeders, fruit trees and garden plots with bulbs and seeds.https://wdfw.wa.gov/sites/default/files/publications/00639/wdfw00639.pdf

 

Next is this charming blog by a New Yorker, Melissa Cooper, who was visiting Garden Bay and enjoyed observing our local Douglas Squirrels.https://outwalkingthedog.wordpress.com/tag/wildlife-british-columbia-sunshine-coast/

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