Glenn Hori – Worth A Dam

Up in the air and over the wall,

Till I can see so wide,

Rivers and trees and cattle and all

Over the countryside—

Robert Louis Stevenson (The Swing)

You won’t wonder at all why I started this post with that particular poem of my childhood when you see this recent photo of the Napatopia beaver habitat. Guess who went out and purchased a drone? This photo was taken at 105 feet.

Just to get you oriented the green part is Tulocay creek, and to the left of that is the Westin Suites and parking lot. The water flows towards the bridge. About a third up on the left is that beautiful lodge of theirs smartly anchored to the dead tree. About a third from the end near the bridge you can see a stand of tulles where the dam is. And then the mostly dry creek continues on with plant and brush growth after that.

Beaver dam from 105 feet — Tulocay beaver pond at 105 feet: Rusty Cohn

This really shows the many benefits that an urban beaver pond can give to a constrained city creek. Flora, Fauna and biodiversity boosts galore. Thanks Rusty, for sharing the results of your new toy with us. We only wish Martinez still had a dam we could talk you into photographing next!

Speaking of amazing photos not taken by us, this photo series was posted on Facebook this morning by Glenn Hori, an old friend of the Martinez Beavers. He wisely chose them in honor of Labor Day. He says they were taken on July 16. Such a hard working beaver! It breaks my heart to think these photos are Jr. bravely doing her job right up until the end. But it’s good to remember what a fantastic craftsman she was. (Click twice on the photos to enlarge.)

I’ve got one more picture to share, and that is the result of many hours labor on my part. I made this as a graphic to use with Audubon, starting with the silhouettes of our beavers and adding everything else in layers. I can’t begin to describe to you the amount of work something like this takes with my hokey little graphics program, but I’m proud of the result. How many bird species do you recognize?

CPU stands for “Catch Per Unit” of effort. Tidy description eh? It is an actual measure used in actual research and actual population monitoring. See when the CPU gets lower we can infer the population is dropping. And when the CPU is more productive that means the population is rising. The unit in question is most often time. How many hours did it take for you to kill that many animals? Apparently our government agencies charged with stewardship don’t actually need to spend hours tracking or monitoring the population to understand these complex trends: We just need to ask the folk who are catching them how hard they had to work! Hey, why use time at all? It’s so ephemeral and who wears a watch anyway?

Why not BPU’s? (Number of beers consumed.)

Although used most often for fish, it was discussed in Oregon applied to beavers as well. See the CPUs for beaver are going down in Oregon, which lead to a voluntary moratorium on trapping in some parts of the state. I assume the CPUs for beaver are going up in Massachusetts, which is why folks always complain the population in the state is exploding.

Of course it doesn’t take into account the variability of Effort or Motivation or Skill. A place with trailing interest in/understanding of beavers could produce a low CPU and a place where everyone loses their collective minds when one is seen (Like MA for instance) could produce such a fire alarm effect that their CPU could be quite high. Not all beaver trappers are created equal.

In case it wasn’t clear, I don’t much like the statistic, or the idea of using murder rates as a way of tracking population. But I do like this one odd fact.

The CPU for Martinez California plummeted in 2007 to exactly zero.

Now for something completely different, I was sent this video yesterday by our old beaver friend and photographer Glenn Hori.