The following video shows something that I bet you've never seen. It was definitely new to me. Those ultimate cam-masters, David and Laura Hughes, sent along a new crop of animal videos from one of their magical Monroe County game trails. This one depicts a Beaver, Castor canadensis, maintaining its pelage. Dave and Laura had sent along another Beaver video previously, and I expounded a bit about their engineering feats IN THAT POST.
This time around, the Beaver has the good manners to stop right in front of the trail cam, plunk down, and begin oiling its fur. Beavers have a pair of glands located near the tail - the castor glands - that exude an oily water-repellent secretion known as castoreum. The castoreum is the fourth tier of protection insulating the animal from the icy waters of winter. A beaver has a dense layer of fat, overlain by a dense cloak of short underfur. Overtopping that are longer and coarser guard hairs. The final protective coat is the castoreum, which we see the beaver applying in Dave and Laura's video. With all of these protective layers in place, water has no chance of penetrating to the Beaver's skin, and the furry engineers can operate with impunity, even in the frigid winter waters.
People have found uses for castoreum, too. It is used in various products as a food additive, and also in some perfumes. Glamorous models strutting the runways scented with Beaver castoreum probably do not know that fur trappers also use the pungent mask as a lure for other animals.
Thanks, as always, to David and Laura for allowing me to share their work.