Beaver bits

Recalling a time long past when a young combat engineering lieutenant was trying to build a road through a piece of Canadian boreal forest, I was reminded of the long fight he had with a group of beavers. The little beasties would wait until the construction crew had finished for the day and then, during the wee hours of the morning, construct a dam across the culvert beside the road, totally flooding the good lieutenant's masterpiece.

It was an extended battle which the lieutenant lost despite the fact that he relocated the road several times. My involvement was that of a mere observer, but we all watched as the lieutenant slowly went mad, totally baffled as to why the beavers followed him and continued to destroy his project.

What got me here was reading a bit put together by Jill Harness which led me to this:

Humans have always marveled at the beaver's ingenuity since he always picks the narrowest part of the stream for the site of his dam. This fact was always cited as proof of the beaver's intelligence and engineering skill. Yet even a modest acquaintance with beavers will soon reveal that they are far from cunning beasts. It was at this stage of the debate that a young grad student entered the scene and began to investigate.

Ah! Nothing like working on a PhD to solve a problem.

He noted that beavers living in ponds and lakes and along rivers never build dams - so this compulsive beaver barrier building business was not a result of their busy nature since non-dam building beavers found an outlet for their busy-ness in some way other than dam building. He therefore obtained several pairs of beavers (all with proven dam building track records), released them in different environments and then sat back and watched what they did. Those released in ponds and large rivers burrowed into the bank, set up beaver housekeeping and then showed no more desire to construct anything beyond their holes. Those released along streams, however, found likely looking pools and then proceeded to deepen them by constructing dams at the narrow, shallow, downstream end.

Keeping in mind that all of them had extensive dam building resumes.

So he proceeded to a riffle (the shallow, high gradient part of the stream) and set up a tape recorder to tape the sound of the water rushing over the gravel and stones. He then set up speakers around known beaver haunts and at dusk turned the tape on.

Lo and behold when he returned the next morning he found the speakers buried under several feet of sticks, gravel and mud - thus effectively silencing the sound. The result was the same whether done along a beaver dammed stream, a large (and quiet) river or a lake or pond. The beavers always covered the speakers until they couldn't hear the sound of rushing water.

[...]

Based on experiments with both free living and captive beavers the researcher found that the sound of rushing water was as annoying to a beaver as the sound of fingernails on a blackboard is to humans. And that beavers will pile up sticks and mud in any spot they hear that sound until they can no longer hear it.

There may be other reasons, but I hope the once-lieutenant finds this and realizes it wasn't really personal.