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Elusive Critters - Newsletter Theme

There are many wildlife species that you will have experienced in your travels but never really taken notice of. In this issue of Eyes on Wildlife, you will find profiles of critters that are not frequently seen, not generally noticed and/or not appreciated. These creatures are common and can be observed if you take the time to look at the right time of day or night, in the best season or in the correct habitats.

In some cases, you may not observe these animals directly, but you may see signs of their recent activities. Take some time to learn about the less obvious wildlife around you. You may be greatly surprised by what you discover.

They often have unusual habits and characteristics that will surprise you and cause you to better appreciate these usually elusive critters.

Possum Country - Lower Mainland

You’ve probably seen an opossum and didn’t know it. While the Lower Mainland contains a healthy population of these unusual critters, your first sighting will likely be of a dead one along the road. Even though your odds of seeing one are low, once you learn a bit about their habits and characteristics you will want to keep watch for these secretive animals.

The North American Opossum (Didelphis viginiana) is the only member of the marsupial family found in North America. A common characteristic of marsupials is the female pouch used to carry young. Other well-known marsupials include Australia’s kangaroos and wallabies.

About the size of a small cat, opossums have a pointed snout, naked ears and a long, scaly tail. They are generally grey in colour with the face lighter then the body, usually white. Males (1.5 to 4.0 kg) are slightly larger than females (1.4 to 2.9 kg).

These unique critters are predominantly nocturnal, live a solitary lifestyle and do not hibernate during the winter. They can run at speeds of up to 7.5 km per hour.

Opossums are omnivorous, eating a wide variety of both plants and animals. Main foods include small mammals, birds, amphibians, reptiles, earthworms, slugs, snails, insects, fruits and other plant materials (berries, grasses, leaf litter). They will eat carrion and garbage as well as pet food from bowls left unattended overnight.

Opossums have an opposable thumb on their hind feet. This thumb, along with friction pads on their feet and a prehensile tail, provide a firm grip on branches when climbing in trees and bushes.

It may surprise you to learn that opossums don’t usually live more than 4 years, with the average life span being 1.3 years. To compensate for this shortened life, this species is a prolific breeder.

Opossums have a fascinating lifecycle. Females mature at about 6 months and are then capable of bearing young. A female may have two litters each year, with the average litter size of 6 to 10 young. Gestation lasts about 13 days and the newborns are blind and naked with well-developed forelimbs and under-developed hind parts.

After birth, the young move on their own into their mother’s pouch where they attach to one of her 13 nipples. How a newborn, only about 1.4 cm long, manages to find its mother’s pouch is not fully known. Scent is thought to play a role. How the newborn physically moves to its mother’s pouch is best described by Dr. van Zyll de Jong in Handbook of Canadian Mammals (Volume 1):

    While giving birth the mother sits up and a young invariably travels up until it reaches the pouch. As the newborn opossum has not developed an inner ear at this stage, and therefore cannot distinguish up from down, it cannot use gravity to guide it. The reason it always moves up has a simple mechanical explanation. The body pivots on the well-developed forelimbs while the hind end is pulled down by gravity. As a result a movement can only take place in one direction, up.

The young will spend 55 to 60 days in their mother’s pouch and at about 70 days begin to make short trips outside the pouch. They are weaned and independent at about 100 days of age (just under 3.5 months).

The range of opossums in British Columbia is generally limited to the lower Fraser Valley as far as Hope. Our population moved northward into British Columbia from Washington State where opossums were first introduced in 1920. BC’s first record sighting dates back to 1946 in Cloverdale.

A few opossums were introduced to Hornby Island in 1986. Their numbers expanded rapidly due to a lack of natural predators. There has been a concern about opossums eating substantial amounts of fruits and other vegetation, small mammals, and birds and their eggs on the island. A more serious concern is that opossums will spread from Hornby Island to Vancouver Island where they will be much more difficult to control. While about 600 opossums were trapped on Hornby Island in 1988 there still remains a significant population. Two confirmed sightings were made in Victoria in 1992. Since that time there have been no new sightings.

While opossums manage to survive well in urban areas, they prefer woodlands, especially in the vicinity of streams, and agricultural areas with sufficient cover. They establish dens but seldom remain at one den site for long. Opossums can’t excavate their own dens so they utilize existing underground burrows dug by other mammals, rock crevices, old stumps, hollow trees, woodpiles and abandoned crows’ nests in trees.

A den is filled with dried grass and leaves to form a well-insulated nest. Mouthfuls of nesting material is carried to the nest in its coiled tail.

The best-known behaviour of this critter is feigning death, also known as “playing possum”. When in danger, an opossum will first hiss and growl, lunge at a predator and then try to escape by running away or climbing a tree. If this does not succeed and the opossum is “trapped“, it instinctively falls down on its side with its mouth slightly open and tongue partly extended. To make itself less attractive to the predator, it may also defecate, give off a bad smell and drool.

Another interesting characteristic of the opossum is its method of thermoregulation. Dogs regulate body heat by panting. Many creatures, including humans, reduce body heat through the evaporation of sweat. Opossums lack sweat glands. They reduce body heat partly by licking their forefeet, hind limbs and tail, applying large amounts of saliva. Body temperature is reduced through the evaporation of the salivated parts.

Under the Ground - Moles and Molehills

You may not appreciate those small mounds of soft, loose dirt that mysteriously appear on your lawn. Before you go wild trying to eliminate those brown piles dotting the landscape, give a thought to the creature who created them.

British Columbia is home to three species of moles whose range is limited primarily to the lower Fraser River valley. The most common species, the Coast Mole (Scapanus orarius), is the likely creator of your molehills. This critter will inhabit a range of habitats but prefers well-drained soils and avoids flooded lands.

While infrequently observed, the activities of the Coast Mole are readily obvious. Moles excavate a series of tunnels. Deeper tunnels (7 to 20 cm) make up the home burrow system while tunnels nearer the surface are used for hunting food, dispersal or finding a mate during the breeding season. The tunnels near the surface rarely result in the creation of molehills.

The front feet are broad and shovel-like with long flat claws. It is the front feet that are used for digging tunnels. The excavation of deeper tunnels is best described by Donald and Lillian Stokes in Guide to Animal Tracking and Behaviour:

    To make deeper tunnels, the mole scrapes in front, first with one foot and then the other, occasionally scraping back the loose earth with its hind feet. After a portion of soil has accumulated behind it, the mole turns around and, twisting its head to one side, puts its foot in front of it and bulldozes the soil out of the tunnel. The soil is pushed out through a hole onto the surface of the earth and becomes mounded above the hole, creating the proverbial molehill. As the mole lengthens the tunnel, it makes new vertical exit holes through which to push out the newer earth more easily.

Most of these new tunnels are created in spring when the mole is cleaning out its tunnel system and in the fall when the mole moves back into its deeper tunnels.

Moles are not easily confused with other small mammals like mice, shrew and voles. The large front feet are a give-away. Their eyes are very small and there are no external ears. The snout is long and almost naked. Moles have short, very soft, velvety fur that lies neither forward nor backwards. Most mammals have fur that lies front to back. This nondirectional fur allows the mole to move within its tunnels with ease both forwards and in reverse.

The main food consumed by moles is earthworms. It has been estimated, by David W. Nagorsen in Opposums, Shrew and Moles of British Columbia, that a population of ten Coast Moles per hectare would eat some 219,000 earthworms every year. Moles also consume snails, slugs, millipedes, centipedes and various soil insects.

The pest status of moles is exaggerated. Don’t panic the next time molehills appear in your yard. Use a shovel or small trowel to carefully remove the excess dirt from the surface. You can co-exist with this tunnel-dwelling creature.

A Vole You Say? - Not a Mouse or Mole

The Townsend’s Vole (Microtus townsendii) is a common resident of Lower Mainland fields and meadows. This small mammal is quite different from a mouse and a mole. A vole has a stout body with short legs, short tail and inconspicuous ears and eyes. A mouse has large, conspicuous eyes and ears, and long legs and tail.

It is relatively easy to determine if a field, pasture or meadow is inhabited by voles. They create a maze of surface tunnels in tall grasses. These tunnels are continually maintained by nipping the grasses along the bottom and sides. To find these tunnel systems, look for small round holes about 4 cm in diameter. These holes are easier to find from fall through early spring. The tunnels are also used by shrews and mice.

Voles are generally active throughout the day and night and throughout the year. This species is rarely observed in the wild as voles tend to stay hidden in their tunnels and run away from you when you walk across a field.

The population of voles in a specific area can increase amazingly quickly. Females can have 2 to 3 litters of 2 to 4 young every year. The young are independent within 2 to 3 weeks of birth and young females can reproduce when only 3 weeks old (a few days after being weaned).

Voles feed primarily on grasses and other types of plants, including leaves, stems, roots, fruits, seeds and flowers. They may also consume insects, fungi and carrion. Grasses contain tough and abrasive cells that wear down teeth, but a special adaptation allows voles to eat grasses. Their teeth grow continuously.

Even though you may be hard pressed to observe voles in the wild, despite the presence of large populations, other wildlife have no trouble finding them. Voles are a main food of Barn Owls, Short-eared Owls and Northern Harriers. When you observe a harrier hunting in a field it is probably looking for voles.

Festivals and Events - Celebrate Wildlife

During the spring and early summer months there are many wonderful opportunities for you and your family to celebrate wildlife. Many festivals and special events are held throughout British Columbia. You can experience the thrill of watching thousands of birds on their spring migrations, release young salmon into a local stream, take a walk in the outdoors with an experienced guide or attend a special presentation. For more information on upcoming events visit the festivals and events section of the British Columbia Wildlife Watch web site.

Flying Squirrels - Do They Really Fly?

Have you ever wondered what’s in a name? If you took some names literally, then you would expect Northern Flying Squirrels (Glaucomys sabrinus) to actually “fly”. In fact, they only glide, and always at a downwards angle.

Flying squirrels have a loosely fitting skin that extends on each side between the foreleg at the wrist and the hind leg at the ankle. When gliding up to 45 metres or more between trees, the flying squirrel leaps from a tree trunk with legs outstretched and the fold of skin acting like a combination parachute and sail (or glider wing).

While gliding the squirrel can turn as well as change the glide angle. The tail acts as a rudder. Just before landing, the squirrel drops its tail and lifts its forequarters while slackening the flight skin which then serves as an airbrake. The Northern Flying Squirrel lands lightly on all four feet and then immediately scurries around to the other side of the tree trunk in case a predator has followed the flight.

The Northern Flying Squirrel is quite common but because of its nocturnal habits, it is seldom observed. This critter is found throughout the province, with the exception of Vancouver Island and the Queen Charlotte Islands. Seven of the fourteen subspecies found in Canada reside in British Columbia.

This species does not hibernate in winter. However, adults frequently nest communally in order to keep warm during the cold nights.

The best time of day to watch for Northern Flying Squirrels is about halfway between sunset and darkness. It prefers forests composed primarily of coniferous trees.

Main food sources include leaves, buds, fruits, shrubs, nuts and seeds. Insects, small birds and eggs are consumed when available.

Nests are usually located in tree cavities and are lined with sticks, shredded bark, mosses, lichens and other soft plant materials. These squirrels have been found to nest in larger bird boxes placed on coniferous trees.

About 20 large bird boxes were placed in the mixed coniferous forests of Minnekhada Regional Park in Coquitlam by the Burke Mountain Naturalists in the early 1990’s. It only took a few months for almost all of these boxes to be utilized by Northern Flying Squirrels. Each box was filled with soft, dry nesting material, especially mosses which filled the box above the round opening. On one occasion when a box was disturbed in early spring, four adult squirrels were observed fleeing the box.

During their nightly travels through the forest in search of food, Northern Flying Squirrels may become prey for one of our larger owl species, such as the Great Horned Owl, or other nocturnal predators.

Sources - For More Information

For more information on the wildlife species profiled in this issue of Eyes on Wildlife, consult the following sources:

  • Mammals of British Columbia, Volume 2 – Opossums, Shrews and Moles
    by David W. Nagorsen (1996)

  • Handbook of Canadian Mammals, Volume 1 – Marsupials and Insectivores
    by C.G. van Zyll de Jong (1983)

  • The Mammals of Canada
    by A.W.F. Banfield (1974)

  • Little Mammals of the Pacific Northwest
    by Ellen B. Kritzman (1977)

  • Guide to Animal Tracking and Behaviour
    by Donald and Lillian Stokes (1986)

Bird Tracks

Great Blue Heron Nature Reserve

    Located in southwest Chilliwack on lands previously part of the local military base. From the adjacent dykes the nests of the heron colony are easily spotted when the leaves are off the trees. During the nesting season, when leaves hide the activities of the nesting herons, you can observe a steady stream of adults entering the colony. Shortly after an adult arrives, the squawking of the young is clearly heard. This site is accessed from the Yale Road West exit off Highway 1 and is situated at the southern end of Sumas Prairie Road.

Colony Farm Regional Park

    Located in Coquitlam and Port Coquitlam along the lower reaches of the Coquitlam River. The extensive old farm fields provide perfect habitat to observe the signs of both mole and vole activities. Coyotes, Red-tailed Hawks and numerous other raptor species and Short-eared Owls are frequently observed. Great Blue Herons have a nesting colony nearby. Even a nursing bat colony resides in an old building. The best access is via Colony Farm Road off Highway 7 near the Cape Horn Exchange.

Hicks Lake Outlet

    Located in Sasquatch Lake Provincial Park just north of Harrison Hot Springs. The outlet stream of Hicks Lake is used by spawning Rainbow Trout. Viewing occurs during the months of April and May. Enter the park and follow the signs to the Hicks Lake area and then take the turnoff to the Beaver Pond Trail parking lot. A trail leads to a bridge crossing the stream from where trout are often seen. Also, take 25 minutes to explore the trail around the beaver pond. New interpretive signs provide information on viewing opportunities.