18: Beaver

Hi to one friend specifically,

I write to you from Arapahoe, Ute, and Cheyenne land. I am interested in learning about the different animals that live in the place where I was born. I want to mention that biological classification as taught by western science has its roots in racism, sexism, and transphobia – here’s a good explainer about why.

This is the most anticipated edition of this newsletter yet by at least one reader. Today we’re going to talk about a pretty cool animal, the only one I know of who has been vocally supported by the Libertarian Party gubernatorial candidate and whose busy handiwork has shaped a lot of the landscape – the beaver (Castor Canadensis). As an archaeologist, I am always interested in animals using tools and beavers are a remarkable example. They are a keystone species whose engineered environment provides a suitable home for many other animals. Indeed, nearly every paper I found about beavers in Colorado when searching Google Scholar talked about the positive impact that they have on other creatures.

Beavers are the largest rodent in the United States – they can weigh up to 65 pounds (that’s 4.6 stone for our British readers)! Unique among rodents, they have iron in their tooth enamel, which gives their teeth an orange appearance. When I was doing research about beavers, I stumbled upon a paper where scientists studying tooth enamel tried to say that the beaver “has shown us a way to improve on [human] enamel.” Obviously the scientists wanted to look at beaver teeth but needed to convince their funding body that their research would have an impact on human health. I am disappointed that my dentist has not contacted me about coating my teeth in iron.

We all know that beavers build dams and lodges (lodges are really cool – check out this cross section!) where they live in a monogamous pair with their kits and yearlings. But why do they do that? Beavers, like many mammals, had an Ice Age stage (Castoroides) where they were to my primitive homo sapiens brain alarmingly big – in their case, about the size of a modern black bear. Prior to that, around 24 million years ago, when the Earth was first cooling towards the Ice Age, beavers began to construct their landscape in a way we would recognize today. Eating trees seems to have been an adaptation to living in a cold environment and exploiting available food resources for beavers, who are vegetarians. Building dams and lodges seems to have sprang from that – and we have evidence for it from the Upper Pleistocene (126,000 to 11,700 years ago). I think this study qualifies as beaver archaeology and I would LOVE to excavate a giant beaver’s lodge.

Beaver tails are almost solid fat aside from the rigid tail bone, and were a delicacy for trappers. Want to eat one yourself? Here’s directions on how to cook it. The cool thing about the tail is that it acts as a temperature regulator, and just by keeping the tail in cool water, the animal can keep its entire body at an optimal temperature in hot weather.

Here’s another fascinating beaver fact: they have a cloaca, just like all reptiles, birds, amphibians, and only a very few mammals – almost all of those mammals who have evolved under isolated circumstances, like the monotremes of Australia/New Guinea and tenrecs of Madagascar. Scientists believe beavers evolved them to lower chances of infection from being constantly submerged.

Beavers were hunted almost to extinction in the 19th century (sensing a theme on the newsletter…) and as a result have been reintroduced many places. This included being parachuted into Idaho.  I personally am not a fan of this story because while it provides some funny visuals, I have to think that the poor animals were very scared. Then again I am also scared of parachuting out of a plane – maybe that’s my bias creeping in, and they had a great time. They have also been reintroduced on Zuni lands in northern New Mexico where within three to five years of 23 beavers arriving, local plants were improving, a particularly invasive tree species was dying out, and the Willow Flycatcher, an endangered bird that likes to nest in riparian areas, had moved into many new areas around new beaver dams.

Finally, please enjoy this short collection of “Beaver Problems” compiled by Colorado Parks and Wildlife – beavers take revenge for humans treading on their habitat. Oh, and this beautiful photo, which, along with the lodge diagram, is from here.