Beavers: Dam builders extraordinaire

By Steve from washington, dc, usa - American Beaver, CC BY-SA 2.0, Link

The beavers or castor canadensis ( North American) and castor fiber (Eurasian) are the two species left of the family castoridae (from the anal secretion called castoreus). They probably evolved in the Miocene epoch(23 million years ago). Their nearest relatives are Dassie Rats and not muskrats as previously thought. The word beaver originates in old german and equates to bright brown. Quite appropriate, for their skin is that color and is bright due to the aforementioned secretion; quite necessary for a partially aquatic creature.

They are the second largest rodent in the world, achieving a weight of 45 to 60 lbs. and a length of 40 inches. The capybara is also a semi-aquatic rodent. I wonder if both the creatures sizes have to do with the fact that large bodies are actually better adapted to aquatic living.



They also have wonderful adaptations for their habitat. Webbed feet make swimming a breeze. A heavy coat of hair was a boon to stay warm (that is until humans began making tools to skin them, of course). They can remain underwater for 15 minutes and also have a set of transparent eyelids that function like goggles. Their fur is naturally oily and waterproof, again due to the castoreum from anal glands. The tail functions both as a rudder and also as a fat storage device. Their teeth are also very well adapted to feeding on bark, with the inner edge wearing off more than the outer edge making it easy to shear bark from trees. Contrary to popular perception, they don’t tear down every tree they chew on.

They are mostly known for shaping the natural surroundings to their advantage by building dams and colonies to stay warm and comfortable in winter. The dam slows the flow of water so the lodge and food cache doesn’t wash away.

Beavers were plentiful in the Americas before the colonization by the europeans who mainly came in with the various East or West India companies. The largest operation was probably run by the Hudson Bay Company and almost led to the extinction of the beaver. However, better sense prevailed and there are few beaver culls these days. It is now the symbol of Canada and adorns numerous coats-of-arms and other very serious official seals.

Beavers live in families of about 8 individuals consisting of a monogamous pair with kits and yearlings living with them. The young are born in litters of 1 to 6 kits around May-June and are weaned in two weeks. Beavers live relatively long live of 20 years in the wild. These days, they are slowly coming back to areas like manhattan ( the area of Times Square was once a beaver lodge) that they inhabited ages ago. May they long stomp their tails ( a sign of warning) at all ill-omen.

About mammal 73 Articles
I blog about mammals and all the interesting and fun-filled facts about them will be welcome additions to this blog.

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