Do beavers think?

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Lily Pond: Four Years With a Family of Beavers, by Hope Ryden (1989).

One good thing about having a really active dog is that I end up taking her on lots of walks in the woods.  She needs good exercise every day, regardless of weather, temperature, or season.  It’s been a real treat to explore the outdoors with her in all seasons; there’s always a lot to see.

In the past year, we’ve had several interesting encounters with beavers.  The most startling was this spring, when a beaver lumbered across the trail right in front of a man and his wildly barking dog.  I saw it from a distance and couldn’t really believe how nonchalant it was in the face of excited dogs.  It swam across a narrow open lead of water and hauled itself out onto the ice, where it sat chewing on twigs, completely unconcerned that we were watching from 20 feet away.  It was huge– maybe four feet long from nose to tip of tail.  How big do these things get, anyway?*

So it seemed natural that I’d chose Ryden’s book on beavers, in hope that it would answer a lot of my questions.  Ryden, a naturalist who has also written on coyotes,  spent four years observing beavers in a series of ponds in a state park in upstate New York.  The book is a classic example of animal observation in the wild, from the challenges of learning to identify individuals to acclimating them to human presence to the (inevitable) emotional investment in the health of the colony through harsh winters.

I was intrigued by the book’s central thesis, that beavers are not dumb animals governed by instinct, but that they are actually capable of thinking.  Ryden gives numerous examples of apparently conscious decisions that the animals made, like deciding when to repair a break in a dam as opposed to instinctively filling a gap when they hear the sound of running water.  The idea of animals as thinking beings– clearly a major debate at the time (1989)– now seems so reasonable that it simply isn’t questioned.

Overall, the book is really focused on the social history of this one colony, rather than beavers in general.  The most “useful” tidbit for me was on scent-marking.  Beavers create small heaps of muck and vegetation around the edges of their ponds, then mark them with castoreum, a sweet-scented secretion that people use in some perfumes.  I call this useful information because it helped to solve the very minor mystery of why my dog flung herself down on a wet mucky boulder at the edge of a swamp and rolled around madly.  The dog usually rolls in something that stinks to high heaven, but, remembering the beaver marking, I bravely (foolishly?) knelt down and sniffed the mucky little pile.  Surrounded by fetid swamp water and the smells of rotting vegetation and rampant spring growth, I caught a whiff of the loveliest sweet lilac scent!

*It turns out that a large beaver can weigh as much as 70 pounds– twice the weight of my dog!

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