The Beav

Whistler Naturalists

Springtime has come; the hummingbirds are back, the bears are feasting on skunk cabbage and grass, and our largest rodents, beavers ( Castor canadensis ), are very busy. Walking the valley trails near any waterway nearly always results in signs of recent beaver activity: newly felled trees, stripped shrubs, fresh dams, flooded ponds. Over the winter, deep snow cover prevented any home and pond maintenance activity for these aquatic animals, so now they need to repair and rebuild their dams and lodges and prepare for the birth of this year’s kits. All of these repairs mean the beavers need significant amounts of building materials in the form of trees and limbs. The results of their activity are obvious throughout the valley.

Beavers typically live approximately 15 years in the wild and are monogamous, mating for life or "remarrying" upon the death of their mate. Beavers typically share their home pond and surrounding habitat with several years’ offspring until the youngsters move on to establish their own territories – sometimes nearby, or even several hundred kilometres from their parents.

Beavers are remarkable water-dwelling mammals, perfectly suited to life in and around water. They can close their eyes and still see under water (thanks to a second transparent "eyelid"). They can also plug their nostrils and ears with little fleshy flaps which they use when diving under water. They can easily hold their breath for a good 15 minutes – and during these longer dives blood is diverted from their cold paws and tail to their brain, maximizing oxygen flow where it is most needed. Of course beaver fur is well known for its nearly perfect waterproof and heat-retention qualities.

Somewhat awkward on land, once in the water beavers are powerful and expert swimmers. Their flattened scaly and muscular tail and their large hind feet are used for underwater propulsion and steering. They also use their paddle-like tails for signalling – there’s nothing quite like a heart-stopping warning slap of a beaver’s tail during a peaceful evening canoe paddle on a quiet lake. Anyone who has heard that gun-shot-like sound knows how effective the signal is at alerting anything nearby of intrusion into a beaver’s home territory.

But some people view beavers negatively. From an economic point of view, damage incurred from beavers by "nuisance activity" can be costly: damaged trees, unwanted flooding of lands and roadways, and the damming of culverts usually make for unhappy landowners. It is estimated that negative economic impacts from beaver activity exceed the value of their harvested pelts in the United States (which is in the millions). So what? I argue that the ecological benefits from beaver activity far outweigh any perceived or real negative economic impacts in the short-term.


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