My Mom and Dad took us to Rocky Mountain National Park in October, and we heard a talk on beavers given by a park ranger.  She started out her talk by comparing beavers with Olympic swimmers.  An Olympic swimmer has goggles, but a beaver has an eye membrane that closes over its eye when it dives into the water.  Olympic swimmers have rubber caps to keep aerodynamic, but a beaver is shaped like a torpedo and also has an oil gland under its tail and a split claw on its left hind foot that it constantly uses to spread the oil on its fur so that it can speed through the water.  Another key that makes an Olympic swimmer a good swimmer is that he has flippers that help propel him through the water.   A beaver may not have flippers, but it does have large feet so that it can swim fast through the water.  An Olympic swimmer has ear plugs and nose plugs to keep the water out; similarly a beaver has valves in its nose and ears that automatically close when it dives in.  An Olympic swimmer has a wet suit for warmth and waterproofing, a beaver has a very thick tuft of hair that runs along its backbone and is so thick that one can hardly see any skin when it is parted.  Like the swimmer’s wet suit, this hair helps keep the water away from its skin and keeps it warm.  A beaver is more naturally fast in the water than a human, because a human has to wear special clothes while a beaver is made for the job.

A beaver’s diet consists of willow trees, birch and aspen.  It does not eat pine trees, because the sap would gum up its digestive system; it only eats pine trees if it is starving.  It chews down the tree to get the upper branches which are just right for its mouth to fit around, and when all the bark is chewed off, the pine branches go to the dam to patch it up.  The beaver eats the inner bark under the dry outer bark called cambium. This bark has the most nutrition in it.  A beaver’s skull is just big enough to carry a two inch in diameter branch.  Since it would be difficult to for a beaver to stand and chew a tree with just two little legs, it uses its tail to make a tripod. 

To start a dam a beaver has to have land with a grade of seven degrees or less.  First it gets sticks and puts them vertically in the water, then adds mud and more sticks horizontally, then the water is slow enough to build the main dam.  For the first year the beaver digs a den where it mates with a female beaver which has pups. The next summer it is time to build a lodge, and the pups are a great help with making the lodge.  The inside of the lodge is kind of like a human house!  The main part is the family room and down below that is the entrance and beside that is an emergency exit.  The outside of the lodge is so tough that a chain saw would be the only thing that could break through it other than a bear!

Under the beaver’s tail is a perfume gland.  The beaver mixes its perfume into mud balls that it uses to mark the boundaries of its territory.  Beavers are very territorial about their property and they will not let other beavers enter into their territory.  A beaver pup can stay in the lodge until it becomes an adult.  When it becomes an adult the mother beaver kicks it out. 

 
A beaver changes its habitat more than other animals, providing homes and lodges for other living things.  The water built up from the beaver dam makes a maze of small streams with sticks here and there that catch leaves, sediment and other things.  After time the beaver dies or moves and leaves behind its pond, and the dam eventually erodes and the pond drains and leaves behind up to two meters of sediment that had been trapped by the dam!  All the sediment is healthy for worms and makes good soil for plants.  A beaver removes trees around streams and provides sun for flowers and smaller trees.  After an aspen tree has been chewed down by a beaver the shoots come up and they produce a chemical that the beaver does not like, but moose and deer like to eat the shoots. 

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