Sunday, October 11, 2009

A Beaver Family Who's Who

A question I hear often is "How many beavers are there?' Before I answer that let's look at beaver social structure, which is built around a family, also called a colony. A colony consists of an adult male and female plus their offspring from the past 2 years. When young beavers reach their second birthday they leave the parent colony and wander far and wide seeking a mate and a place to set up their own colony.

Back at the home colony, the adult female produces a new litter of usually 3-4 beaver kits every year. The number of kits depends on the body condition and age of the adult female. If she is young or in poor condition fewer or no kits will be born. I know the Maxwell Lake beaver colony had at least 4 kits in both 2008 and 2009 because I saw 4 kits at one time in both years.

The next consideration is the fact that beavers are very territorial. All members of the colony defend their territory against any strange beaver, so all beavers seen in Maxwell Lake and upstream and downstream along Happy Creek for a few hundred meters are members of the Maxwell Lake colony. There are several other colonies further up Happy Creek above the powerline crossing .

Now we have all the pieces to answer the question. Assuming all the kits survived, there are at least 10 beavers in the Maxwell Lake colony. I've personally seen 7 at once in 2009. There could be more than 10, but that's my best estimate.

Update October 20, 2009 This evening I saw 5 kits at the same time, so I'm upping my estimate to 11 beavers for this year: 5 kits, 4 yearlings, and 2 adults.

The best time of year to count beavers is from June-August after the kits are born and are active around the lodge. That's when the size difference between the adults, yearlings, and kits is most pronounced and a minimum count of each category is most reliable. Dave Conlin took a great photograph of a Saskatchewan beaver family with 8 members. Check it out and make your own estimate for the Maxwell Lake beaver colony in 2010!

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