Month: April 2011
You’ve probably seen the statistic tossed about that our current beaver population is about a tenth of what it used to be. That’s always seemed right to me, but today I really looked a little closer at the numbers. This article, (which dissapointingly isn’t so much an article as it is the back-of-a-cereal-box collection of facts, some of them accurate), describes a pre-contact population of American beaver at 60,000,000 animals. I was curious how that would actually play out regionally. Leaving out Hawaii which never had beaver, and Alaska which I don’t think was included in this guestimate, that leaves 125000 beavers per state. Not really a helpful statistic when you think about the differing sizes and amounts of water per state.
But what if you look at water miles for the entire contiguous US, Wikipedia tells me we have 160,820.25 square miles of water. Now, this makes a little more sense. 60,000,000 beaver means about 373 beavers per every 27,878,400 feet of water. That works out to be about 46 colonies for every square mile of water. Or if you are looking at the 35,000,000 miles of river in the United States, that’s about 17 beaver per every mile of stream.
17 per mile! That means that the beaver population of Martinez between Safeway and the train station would more than triple. For California’s 7736 miles of stream that works out to be about 131,512 beavers historically. That’s still not exactly right either because some of them were in lakes and larger bodies of water, but you get the idea. That’s A LOT of beaver.
So the next time you read an article saying that the beaver population has rebounded, think about the 90 percent of those numbers that are still missing. I’m not even sure that the existing population of beavers is larger than or equal to the number of beavers killed every year. Does Fish & Game keep those statistics?
Apparently, dog training obstacle courses don’t work very well for excluding beavers (who knew?), and the animals unsurprisingly cease being cute the very moment they begin to cause problems for humans. At least that’s what Bill Bittar says in his new article at Monroe Patch.
Bob and Missy Shawinsky lived and worked in Stamford where he is a police sergeant and she is a teacher, before buying their Huntingtown Road colonial on Gusky Pond in Monroe last February. “It’s beautiful here,” Missy said Saturday morning. “It sure is country. You can see a sign for lamas on the street and we have well water.”
A far cry from the city, the Shawinskys commonly see wildlife in their neighborhood’s natural surroundings, ducks swimming on the pond, birds soaring overhead … and the couple has also had their first encounter with beavers.
“I saw them building lodges and I thought, ‘Oh, how cute,'” Missy said of her first beaver sighting. “Well, it’s not so cute anymore.”
Gosh that is so rare. It almost never happens. A mild-mannered couple move from the city to the country to enjoy nature and appreciate the outdoors and then suddenly discover, without any warning at all, that wildlife can be inconvenient. Those creatures that live in the ponds where you bought your home can challenge human structures, with no concern for you as they maintain their family’s need for food and shelter, and ultimately damage property. Reasonable people understandably want it controlled, so that things work more like they used — back in the city —which they left.
(Come to think of it, this is very common. It happens all the time. It’s not even a “dog bites man” story. It’s more like a “dog scratches” story.)
The author writes that several exclusion devices are dutifully employed around Gusky pond and then says “Public Works uses a backhoe to lift some heavier exclusion devices and shake debris out periodically.” Oh, you mean failed exclusion devices are employed! The kind that don’t work and contribute to the important DEP statistics that say flow devices are useless? No wonder the town’s up in arms over beavers. Never mind that Connecticut is the only state in the country where the Humane Society maintains its own beaver management expert to control beaver problems (ex-trapper Skip Hilliker), or that Monroe is two hours away from Beaver Solutions’ Mike Callahan, or a mere 5 hour drive for Beaver expert Skip Lisle. Why use proven techniques when backhoes are so much fun to operate?
The article does contain one bright spot, an animal Control Officer who knows his stuff;
Monroe Animal Control Officer Ed Risko said the McGunnigles’ well is now underwater from the flooding. The McGunnigles and the Shawinskys are concerned about Giardiasis, an intestinal infection that can be transmitted from beaver to human when feces in flooded water gets into wells. “People claim that, but I haven’t seen that in 20 years,” Risko said of people being infected by beavers. The animal control officer does periodic tests at Gusky Pond and said the test he performed about two months ago did not detect Giardiasis.
Good work Ed, I would add that beaver stools look like sawdust and are less likely to carry giardia that just about any mammal who stops by to defecate in your water, and if they DO happen to contain giardia it’s because they caught it in your water most likely from a human septic problem and I’d be inclined to worry about that anyway.
There used to be limits on beavers, but the population has grown so much that Risko said there are now no limits, according to Connecticut trapping regulations. The state used to allow beavers to be relocated rather than killed, but Risko said relocations are no longer allowed. Beavers are territorial and there are no longer as many places to move them, according to the DEP. “I think there were 24 and they got eight out,” Bob McGunnigle said of beavers in his neighborhood Saturday.
You think there were three families and they trapped one? 33% success rate, not bad. I’m curious, what makes you think there were 24 beavers? You saw three lodges? Three dams? How exactly did DEP come up with 24? Never mind. This is my favorite par part of the article;
Lilipad roots at Gusky Pond. Beavers dig up these roots and use them to sharpen their teeth. Credit: Bill Bittar
Ahh the weapon-wielding fiends! Grimly impressive imagery. But false. Not to sharpen their teeth, Bill. (Trees do that). The monsters dig up roots for them and their children to EAT. They chew lily roots because in the frozen winter they selfishly get hungry and even when they don’t have access to the banks to damage property owners trees, they can eat roots. I believe there’s an entire book about this. You might enjoy it.
In the meantime, you get a letter, and Ed gets a mostly attaboy letter. I’ll write Hilliker that his services might be needed and you are both welcome to pass them along my correspondence to the McGunnigles if you think they’d be interested.
Light beaver blogging as I’m off to school in the city this morning. There’s a nice Martinez Beaver article in yesterday’s record. Some lost details with the family history, but generally a kindly look at our famous colony. If you need a beaver geneology refresher course after reading it, this should get you started. Meanwhile, drop Nancy a note and demand more beaver sounds!
Oh and if you haven’t seen this feel-good remarkable community-activism-on-behalf-of-an-animal video, you really should.

Our friends at Beavers: Wetlands & Wildlife selected this day as International Beaver day, and the good news is it’s catching on. I’m told that today is a great day to give a beaver talk, write a letter to an editor about beavers or set up a display. Hmmm. I already do that on the other 364 days of the year, so I thought I’d do something truly special today. I’ll teach you a brand new thing. I learned about the concept from Michael Pollock on our Yosemite trip, and have been waiting for the right moment to share. Of course the unflattering story line is entirely my own responsibility. I figure a time when we’re waiting for beavers to build is a good time to learn.
‘Only it is so VERY lonely here!’ [without the beaver dams] Alice said in a melancholy voice; and at the thought of her loneliness two large tears came rolling down her cheeks.
‘Oh, don’t go on like that!’ cried the poor Queen, wringing her hands in despair. ‘Consider what a great girl you are. Consider what a long way you’ve come to-day. Consider what o’clock it is. Consider anything, only don’t cry!’
Alice could not help laughing at this, even in the midst of her tears. ‘Can YOU keep from crying by considering things?’ she asked. ‘That’s the way it’s done,’ the Queen said with great decision: ‘nobody can do two things at once, you know.
Consider this then:
A long time ago a tired researcher sat on his lawn chair and glared at the beaver dam in his stream and thought, I really need to blow that thing up, but first I’ll justify it. He took out the thermometer his wife had used to check his daughter’s temperature that morning and he measured the top two inches of water in the pond.
“Ah ha!” he said, comparing it to the top two inches of running water on the other side of the dam. “Beaver dams raise the water temperature and this hurts trout and salmon!” “Beavers destroy habitat for fish!” He trotted back into the house and wrote a paper which was published in the journal of wehatebeavers and soon the paper was quoted in ever other scientific paper on beaver dams known to man kind. (Then he blew up the dam which had been his goal all along, and alot of people were encouraged to blow up their dams too.) Soon every biology, hydrology and icthology student was taught that beaver dams raise the water temperature and regional agencies like Fish and Game or Department of Natural Resources wrote it into their policies and it became the great truth of the land. It was even quoted by the letter I responded to from LADWP yesterday. When a lone graduate student scratched his head and said, how do you know? He was nearly laughed off the campus and his thesis adviser had a tense conversation with his mother in the laundry room.
Hyporheic Exchange (Pronunciation: hi-poe-REE-ick)
So it turns out that when you look at a stream there’s the water you CAN see, the ground water you CAN’T see, and this layer of soggy silt & pebbles that acts as a sponge between the creek bed and the water table. This layer is constantly moving water into the ground, and pulling groundwater back into the stream. Water in the ground is naturally cooler because it gets no sunlight at all so every time it seeps into the creek bank it lowers the water temperature a bit, and when water is returned to the creek bed it is cooler.
Michael Pollock, of NOAA northwest fisheries was interested in this dynamic, and particularly what it meant to that old story about beaver dams choking out salmon and trout. He decided to set up some thermometers at different layers in the water, and also below the subsurface of the stream to find out the truth, then he repeated this at different points along a stream. Before I show you what he found, you need to know that the headwaters of any stream is cooler than the mouth. So we expect the temperature to gradually go up as the water moves down stream.

So reading the river from the headwaters on the right, the blue line is the subsurface temperatures and the lowest, which we would expect. The red line is the surface water of un-dammed areas, and the green line is the surface area in beaver pools. As you can see the red line is consistently higher than the green line, meaning that the surface area of beaver ponds is cooler than the surface area of free-flowing stream, the opposite of what our lawn chair researcher observed. Why is this?
I’m told the next graph has not yet been published so I shouldn’t post it on the web. Okay just imagine that the three measurements are combined we see this gradual sawtooth incline with a huge gap showing that the temperature suddenly falls. And guess where? There’s a huge temperature drop as tons of upwelling water seeps into the banks of the creek. It’s a beaver dam, whose deep pools increase the contact area of the water with the hyporheic zone, so there’s greater exchange and cooler temperatures. Say it with me now, “hyporheic exchange.” This is what the fish like. This is what enlivens the water and makes the creek more healthy. And this is why that researcher in his lawn chair all those years ago should be scornfully forgotten along with his entire findings.
Here’s the take home sentence for you to use in your next beaver argument, and you know you’ll have plenty. “Beaver dams cool streams by maximizing hyporheic exchange.”
Happy International Beaver Day! Celebrate by telling someone you know. Or everyone.