Castor canadensis, commonly known as the North American beaver, is a species with an interesting history. Beginning in the late 1600s and continuing into the early 1900s, beavers were hunted by European fur traders who, disappointed by the absence of spices in Canada, made their fortunes from beaver pelts, used mostly for hats. Because of this exploitation, by the 19th century beavers were close to extinction. Had it not been for the new European fashion for silk hats, the species would not be here today. The beaver, which is the national symbol for Canada and the state animal for both Oregon and New York, is a resident today on my farm in Afton, Virginia. This newcomer has drastically changed the pond on which it lives.

I became interested in the nature of this species, and the dam and lodge it had built. I could see these structures but had never seen the actual beaver; I was only aware of its presence through its handiwork. This was a great mystery to me, because I did not know how these massive structures were built, or why their shape and size changed over time. It seemed to me that once the dam was built and the water level of the pond was raised, there would be no need for the beaver to further change the pond's dynamics. I tested a null hypothesis: that the beaver builds his dam increasingly higher to achieve even higher water levels in the pond.