One of the first steps to understanding animal behavior is to recognize that many species interact with the world through their noses. Beavers are a prime example. Once they establish a territory, they’ll mark it by making little piles of mud and then squatting and depositing scent from their castor glands. These castor mounds serve as posted signs, telling other beavers to stay away, and also as a basic means of communication with other beavers in a flowage. Studies have shown that beavers can recognize family members by their smell, and also distinguish strangers from neighbors. [To learn more about castor mounds check out this article by Dietland Müller-Schwarze.]
We figured that to get a good picture of a beaver we should pretend to be a beaver, so we visited a trapper and procured some fresh castor gland. These glands are located near the anus, and in mature beavers in springtime they’re swollen and impossible to miss. There are two sets of glands in this picture, each worth around $5 to $10 to a gland dealer. They’re used in the perfume industry.
We ground the glands and added a little oil sac, on the trapper’s recommendation. The castor smells sweet – it’s made of recycled plant compounds – and the oil sac smells slightly bitter.
We then set the camera up at the edge of an active beaver pond near the office and set to work making a fake castor mound. Here, editor Dave Mance III starts things off by making it look as if a beaver were coming in and out of the water. The real teachable moment, though, is that if you’re going to be involved in a photo essay, you should really remember to wear a belt.
Here, Mance flings mud up on to the bank, all the while grimacing strangely as if the mud offended him somehow. An actual beaver would have carried the mud wedged between his front paws and chin, all the while looking placidly rodent-like.
Mance then flattens the mud using his hand like a beaver tail…
And then applies a dollop of castor while Stella the dog and Northern Woodlands co-founder Ginny Barlow look on.
Barlow asks to smell the castor…
...that it smells sweet, all the while strategically keeping her face out of the photo, as she’s wont to do.
Then everyone goes home and waits.
Five hours later an adult beaver shows up – probably the male. He smelled the pile and circled it three times, each time knocking it down with his tail. He then squatted over the mud smear and deposited his own castorium, then raked things with his hind feet. The whole process took 12 minutes.
One hour later, two sub-adults showed up. The first one did a modified scent marking routine that took 3 minutes. As he left, the second beaver came ashore, squatted, scent-marked, then left. It took this second beaver only 1 minute to do his business.
The next morning a pair of mallards came to investigate.
Then a random person we didn’t know.
Then Stella, who in this series takes in the new scents, licks everything, rolls in the castor mound, gives a blissful look that only a dog could understand, then finishes it off with a guilty look, in conjunction with her owner’s cry, that says: “Oh right, I’m not supposed to roll in stuff like this.”