cartography

Deer Trail Engineering Question

So here’s a trail the mule deer have cut up a slope above a pumping station in Vernon. They chose an angle of around 20 degrees, except for that steeper bit in the middle.

A fascinating thing is going on there. The cut into the bank turns right here. The deer have chosen to descend right at the point of the turn, effectively turning a bend into a straight plane. A consequence is that there is no matchup between the desired point of descent (a point) and the desired angle across the slope. Coming down, the deer have to reach forward with their front legs, and add extra pressure with their hooves. Going up, they would have to add the same pressure with their back hooves. And those hooves are sharp! They really slice through stuff!

The result is intriguing. By this simple bit of body reality, the flow of the slope is going to change. Instead of water draining off at around a 50 degree angle to the left, the deer have effectively begun to turn the slope. I think we can expect water (and mudslides and gravel) to soon fall straight towards us, pushing the slope back behind the steep bit and causing it to turn at the dip. In fact, you can already see that turn beginning. The continuing effort of getting over the rise and onto the point is going to put increasing pressure on that turn, at the same time that the changing orientation of the slope pushes it ever lower. The result is going to be a steeper and steeper rise. I expect the deer will cut it off soon. What do you think? Are they going to extend the angle of the lower track? Or are they going to match the angle of the upper track with the lower one by stepping up onto the slope above their trail and cutting a new path through it? I think they will go up, as they will meet its invitation from both above and below. Choosing the lower track, on the other hand, is a kind of bit of human forethought, and not-so-deerish, who are wiser with their bodies. Or am I wrong? I hope you’ll weigh in. The deer will answer soon enough!

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