Beaver & Otter Cohabitation
It is not coincidental that you often find otters residing in beaver ponds. There appears to be a commensal (one animal benefits while the other is unaffected) relationship between these two animals. The beaver is unaffected – it is a herbivore, so its food supply is not threatened by the presence of otters. (While an occasional beaver is eaten by an otter, it is a rare occurrence.) The otter, on the other hand, benefits from abandoned as well as active den sites (both beaver bank dens and lodges) as well as an ample supply of fish due to the impoundment of streams by beavers. While I was aware that otters often take over abandoned beaver lodges, I only recently learned that the lodge does not have to be uninhabited for otters to move in. This was confirmed when I discovered a large amount of otter scat (mostly fish scales and crayfish shells) on top of a beaver lodge, right next to the hind foot print of a beaver. Freshly placed sticks on the lodge (it is in open water) indicated that it was occupied by beavers, while an otter’s stream of air bubbles could be seen as it exited the lodge and popped its head up above the surface of the water.
I thought that otters were fierce predators of baby beavers. I would be very pleased to learn that is not the case. Do you know anything about that?
February 22, 2013 at 5:08 pm
Studies on otters preying on beavers are varied, Kathie. While beaver remnants have been found in otters a few times, the vast majority of studies show no sign of beaver ingestion by otters. Perhaps otters, along with two year old beavers, are booted out of the lodge come birthing time!
February 22, 2013 at 5:45 pm
Dr Lynn Rogers (black bear researcher in Ely, Minnesota) once had a camera in a beaver lodge and was able to see muskrats and mink living together peacefully. At least until the day one of the mink ate one of the muskrats. I don’t remember if the beaver was using the lodge at that time.
February 22, 2013 at 5:20 pm
Fascinating, Al!
February 22, 2013 at 5:46 pm
Baaaaaaad Mink!! I have seen Mink hanging about a Beaver Lodge in the late fall. I never gave it another thought till now.
February 22, 2013 at 6:18 pm
Maybe we are looking at a hostage situation?
February 22, 2013 at 5:42 pm
Very good, Elizabeth!
February 22, 2013 at 5:47 pm
Amazing! I wonder if the beavers would really rather the otters weren’t living in there (with a sort of passive aggressive attitude) but the otters just ignore them? Would be so fascinating to view a critter cam inside this lodge. hint, hint…
February 22, 2013 at 9:27 pm
wow, Mary. Is this cohabitation generally known? Maybe you should publish it as a note in some fancy journal.
February 27, 2013 at 9:39 pm
I read about this happening in one of my resource books, which I pretty much trust, but I should do a more thorough search just to see if someone else has observed this!
February 27, 2013 at 10:08 pm