Mysteries Abound

Studying nature, the answers we find lead often to more questions. Mysteries abound, such that naturalists and ecologists frequently act as sleuths in pursuit of clues. Observations feed our curiosity, leading to speculation, reflection, and inquiry.

So I was naturally curious when one of our canoe-program volunteers mentioned that he had seen some unusual markings along the bank of the Kishwaukee River in the Deer Run Forest Preserve. He said it looked like someone had dragged something out of the brush and into the river. When he told me about it, he was helping out with our youth canoe camp, Blazing Paddles. We were going to be paddling that very section of the river and he wanted to know if I could help interpret what had made the marks.

As good fortune would have it, he was able to point out the place along the bank shortly before we directed our pod of teenaged paddlers to pull ashore for a lunch break.

  striations, etched like scratch marks into the sloping riverbank

striations, etched like scratch marks into the sloping riverbank

With a small band of curious campers in tow, I hiked back along the shore to investigate. The markings fanned out from a small opening in the vegetation, as if someone had combed or raked the surface. But this was no Zen garden and there were no trails near this section of shoreline. I ducked into the willows to investigate further.

There, behind the edge of the brush line, the answer was apparent. Sharp stumps of willow, a couple of inches in diameter, bore the grooved channels formed by sharp rodent teeth. Beavers apparently had been taking down willows and dragging them toward the water, stump-first with the upper leaves and branches trailing, raking the surface of the soil.

The adolescent paddlers in my company were impressed, never before having seen for themselves that sort of evidence of beaver activity—and they also were impressed with the beavers’ famed industriousness. We knew that the work must have been recent, as we found additional evidence farther along the bank:  A length of willow trunk, gnawed at the base and bearing the tell-tale tooth marks, still had a few green leaves at the tip. Those leaves would have wilted within days of the stem having been severed.

  evidence of beaver activity; adolescent human for scale

evidence of beaver activity; adolescent human for scale

Beavers (Castor canadensis) are the largest rodents in North America, with bodies reaching 30 inches or more in length. A typical adult beaver may weigh between 35 and 65 pounds, although specimens weighing up to 85 pounds have been reported. Beaver teeth are formidable: the front incisors are oversized and appear orange in color, as iron replaces calcium in the enamel, making the incisors exceptionally strong—capable of gnawing through hardwood trees.

  a stump exhibiting the grooved marks left by a beaver’s tough incisors

a stump exhibiting the grooved marks left by a beaver’s tough incisors

Further adaptations of these aquatic mammals include webbing between the toes of the hind feet and the distinctive paddle-like tails. When startled, a beaver may slap its flat tail in warning as it disappears beneath the water’s surface. Beaver fur was prized by the trappers who were among the first Europeans to explore this area. The outer guard hairs are long and glossy while the underfur is very fine and dense, protecting and insulating beavers’ skin from the water. Oils secreted through glands are distributed and combed through the fur while grooming to enhance the waterproof qualities of the fur. Such musky oils are also used to mark territorial boundaries.

  Physiological adaptations like webbed feet and a flat tail enable beavers to thrive in aquatic environments.

Physiological adaptations like webbed feet and a flat tail enable beavers to thrive in aquatic environments.

Beavers are monogamous and live in extended family units, typically spanning three generations. Their preferred diet consists of herbaceous vegetation, although they will browse on woody stems when necessary.

Of course, we seldom see beavers. Not only are they generally restricted to riparian and pond-side habitats, they also are generally nocturnal, spending the daylight hours in lodges built of branches and accessible through underwater entrances. So, like much of the wildlife with whom we share this little corner of the planet, they may remain unseen, but can be known by their effects.

And beavers can have amazing effects on the environment. They are nature’s environmental engineers; their dams and lodges my redirect the flow of streams and rivers, flooding vast areas and influencing plant communities and habitats over long periods of time.

Nature is endlessly fascinating; collecting evidence, we are drawn deeper into explorations of interrelated phenomenon. Threads lead to nodes that branch off to other threads. One of the things that I find satisfying about studying nature is that we can devote a lifetime of study there and never get to the end of it all. Mysteries abound and there is always more to explore.