Beavers are Natures Engineers Part 1; Beaver Background

A while back I did a presentation for a bunch of 9th graders during their biology camp-out their school hosts annually. While my presentation was geared to entertain these young students, it also had some really cool info I thought many of you fellow steemians would also appreciate!

My presentation was on BEAVERS! Yep, you read that right. Beavers. I know, it sounds pretty silly but beavers are actually a pretty incredible species. They are natures little engineers and are now being used as a restoration tool for riparian habitat.

Photo I took of a male beaver I did a health assessment on

Let me back up just a little bit. First some history on Beavers. Historically there were 60 to 400 million beaver across North America, inhabiting much of the continent. In Utah,(where I live and am familiar with) they not only inhabited much of the state, with the exception of the Great Basin Desert, they were abundant up til 1825. Aggressive trapping occurred in the late 1800’s at such an extreme rate that beavers became rare and were extirpated from many areas. This prompted legislature to close beaver trapping in 1899. By 1912 beavers were making a come back and by the 1950s beaver harvest resumed with occasional site specific closures.

Photo Credit: David Wright

There are currently an estimated 6 to 12 million beavers that occupy much of their historic range. Each state’s wildlife agency manages beavers. Trappers can still trap as many beaver as they would like but now it must be done within a given season in most states (season dates vary among states, and there is no lethal trapping in Colorado). How then are beavers not running a risk of being extirpated like they were in the 1800s you might ask? Well, Beaver pelts are not in high demand anymore and their value has depreciated pretty significantly over time. There are very few Europeans looking to spend big money on a fancy Beaver Hat. Yay! That is great news for the beaver babies who are only hoping to survive.

What do beavers actually do? They remove trees, build dams, dig channels, and build lodges.
First beavers construct a dam (On a side note, I have to retype dam every time because my muscle memory causes my fingers to type damn without any thought and when I reread each sentence- yes I proof read- I see the mistake, so If I miss one, I apologize in advance!) by packing mud, sticks, rocks and debris all the way across a waterway. This backs up water and essentially creates a home range for a beaver. The excess water is used in 2 major ways. First, to expand their reach for food. Channels provide a safe way for beavers to access more wood. They are not agile creatures on land and run a high risk of being snatched up by a predator while trying to gather food. However, in the water, they can escape most predators fairly easily. Second, the deep pool of water that forms behind a dam acts like a refrigerator to store food in. Beavers drag branches and woody material back and stick it into the mud. This keeps the wood fresh throughout winter. Think about how a chipmunks caches seed for the winter. Its similar to this, only, plant material rots or decomposes much faster than seeds do so beavers have essentially engineer a way around this. Put a refrigerator behind a dam. A Refrigerator that can, might I mention, hold upwards of 100 lbs of wood!

Photo Credit: Animal Control Solutions

Once the refrigerator is full, beavers begin building their lodge to provide shelter. They build up mud, rocks, sticks and debris til its above water level. Then they construct a dome over the top of that as a shelter. A Lodge usually has at least 2 entrances underwater to prevent predators from entering while still allowing easy access in and out of their home. The lodge is used as protection from the elements during winter months and to rear young in the spring. It also provides a safe place to sleep year round.

Photo Credit: Cafe Press

I had a really catchy slide at this point in my presentation titled "Chew, Carry, Construct, Repeat!" The 3 C's of a beavers daily life. What I meant by that is beavers will often build dams in series to act as a safety net for huge flood events. Additionally, once a beaver has worked a particular area for a couple years, he will move up or down stream and start this whole process over again.

This process of new dams in new areas every few years has major impacts on stream hydrology and implications for restoration management. Both of which I will discuss in Part 2 of this blog post. For now, I will wrap things up with a fun little story that happened during my presentation. Now I get fairly nervous with public speaking but I was at the end of my hour presentation and all had gone pretty smooth. I thought I had hit a home run. I opened it up for questions and answered several questions without hesitation. At the very end, of course and not surprisingly, one of the students asked how beavers reproduce when they do not have external sex organs. Yes, that is true (I skipped over the anatomy part in this post) but naturally, my response was " I don't have a good answer for you because I have never watched beavers get it on". The entire audience burst out with laughter and I felt my face turn red. I thought for a brief moment I had made it through the presentation without any major "blurps". At that moment, my high fell as I realized I did not quite make it. I should have used much more professional terminology like breed or mate but instead I just had to slip up and say " get it on". Thankfully, I didn't say something worse.

Anyways, keep an eye out for Part 2 in which I will discuss hydrology alteration and restoration implications for beavers.

As always, thanks for reading and if this was interesting to you, don't hesitate to start a conversation or leave a comment!