"Where. Are all. The beavers?!"
According to one of the NPS amphibian crew members last year, this was the question a small boy nearly yelled at them when he found out they were researchers. Apparently, the bison, elk, bears, and who knows what other animals he had seen that day weren't enough. He wanted to see a beaver.
He's not the only one. As the field season carries on, I'm starting to wonder the same thing. Where are the beavers?
I often tell people that despite spending half my summer in their ponds, I didn't see a single beaver or hear a single tail slap last year. In fact, the only beaver I had seen in the wild was on the Laramie River while birding on Big Day in May 2022. That's no longer completely true; I have seen beavers here in Grand Teton National Park, but not while doing my fieldwork.
Just below the Jackson Lake Dam, next to the boat launch, there's a pond. If you're standing on the road and you squint a little, you can see the pointed peak of a beaver lodge on the far side of the pond. Some fish researchers had told me about this pond, and that they had seen beaver there. I stopped by several times during the day before realizing that if I really wanted to see a beaver, I would have to come back at dawn or dusk, when they're more active.
I came back at dusk a few days later and there they were! Two beavs (as my tech and I affectionately call them), swimming around and chowing down on some leafy branches.
And yet, though I now have seen with my own eyes that the beavers are in fact here, in Grand Teton National Park, I'm still asking where they are.
You see, there hasn't been much research done on the beavers here. The main two sources I can find are some papers from the 1970s by T. Collins and some UW-NPS grant reports by W. Gribb and H. Harlow from the early 2000s. There's not a ton up in Yellowstone either, but Doug Smith (the recently retired lead wolf biologist who helped reintroduce the wolves to the park) has at least been doing some regular aerial surveys for beaver lodges and caches (big piles of food they make to get themselves through the winter). None of that work has been published since 2012, though I'm pretty sure the surveys were continuously conducted every two years until Doug's retirement last year.
So the information available is limited. And the information I have says that Grand Teton beavers are on the decline.
Gribb and Harlow conducted aerial surveys for beavers in the early 2000s, and compared their results to what Collins had found through a series of ground-based surveys in the early 70s. They concluded that, from 96 colonies found by Collins, beaver populations had declined by almost 50% to only 46. Estimating that there were approximately 5 beavers per lodge, Collins supposed that the beaver population in Grand Teton National Park consisted of about 500 individuals, and that this was likely closer to the park's carrying capacity.
Why the big change? No one really studied it explicity, but due to a change in how beaver colonies were distributed downstream of the Jackson Lake Dam, Gribb and Harlow supposed it was due to the inconsistent water flows released from the dam, something that Collins had suggested would happen.
I'm not sure this is the whole story though.
The amphibian crews I work with have been monitoring wetlands for over 15 years. Three of the catchments (small watersheds) that they visit in Grand Teton National Park are beaver-influenced. And what they've seen in these beaver catchments is a cycle of beaver activity. Beavers move in, build dams and lodges, leave active sign everywhere, and then they disappear. The dams fall into disrepair, some get blown out. But eventually, the beaver come back.
I got to see this first hand in one of these catchments. In 2021, when I was conducting my pilot season, I joined the crews to get my eDNA samples. While there, we noticed the beginnings of beaver sign. There were no new dams yet, and the largest site in the catchment was a huge meadow. Beaver sign hadn't been seen in the catchment for a few years.
In 2022, we went back, and that meadow had become a lake.
The beaver had built a dam blocking the stream, and it backed up in an extraordinary way, flooding a huge area with a depth exceeding a meter.
This year, the beavers seem to still be active in that catchment.
The super interesting thing about this, is that on the old topographic maps I like to use to navigate by (they're USGS maps from like the 60s), there's a lake, right where that new lake is.
That implies that beaver have been cycling in and out of this catchment for a long time.
But why?
Why invest so much effort into building a dam, creating a lake, just to leave?
Did they leave? Or did they die?
If they died, what killed them? Predators? Disease? Cyclical activity like this actually suggests disease, and there are several things that beaver are vulnerable to, like the bacteria that causes tularemia. Tularemia is even cited as one of the reasons for the decline of beaver north of Yellowstone, in the Absaroka-Beartooth Wilderness.
Having found a dead beaver recently that was fully intact, with no signs of injury or other trauma, disease has been on my mind a lot. The parks service picked up that beaver to conduct a necropsy on it, and I'm still waiting to find out the results. If it turns out to be tularemia, or some other disease, I'm curious how I could incorporate it into my research questions. Disease ecology has never been a primary research focus of mine, but it's something I've found fascinating since reading The Hot Zone: A Terrifying True Story by Richard Preston, about Ebola. One of my favorite podcasts is This Podcast Will Kill You, the hosts of which have PhDs in disease ecology. Maybe now this subdiscipline will move from a casual interest of mine to an academic one. Only time will tell.
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