Otter or Muskrat?

Not a few times, I thought I was looking at a big muskrat only to discover, when I looked closely at the video, that I had seen an otter. Muskrats are rodents like beavers though much smaller, half the length of an otter and a fourth of the weight. They can vary their diet, and like otters do eat shellfish, but they usually feast on grasses and I often see them carrying grass in their mouth as they swim across a pond.

The video clip below is a bit long but it shows the persistence of a muskrat when it's time to feed the mother and young back in the den, which in this case was a beaver lodge which the beavers continued to use, and where, come to think of it, I saw otters park themselves on top on several occasions.

Otters rarely carry grass as they swim in a pond. I once saw an otter put some grass up on a beaver lodge to make it a bit more comfortable for a long mid-day nap. So how did I mistake an otter for a muskrat? It's all in the tails. Muskrat tails are not at all like beaver tails, and when a muskrat cocks it in the air, from a distance, it can look like an otter tail, even though an otter's tail is spade-shaped and a muskrat's tail is straight.

Muskrats often hold their tails out of the water which otters also do when they are diving for fish. The first photo below is a muskrat; the second is an otter, almost all the way under water, so I saw the thinner end of its tail.

However, a few times I've looked at the video I took of what I thought was a muskrat only to see that I actually saw an otter. Unlike the beaver, both the otter and muskrat can propel themselves with their tail. So when a small otter is simply swimming through a pond without diving for fish, you might see the tail swishing a little behind it and think it is a muskrat. In the photos below, muskrat first, then otter.

An otter's wake is always bigger and an otter is faster, though a muskrat can sometime rotate its tail fast enough to make like a jet ski! (See my web page on muskrats.) Finally both otters and muskrats have the habit of climbing up on logs floating in a pond. Again, muskrat first, then otter.

The otter has much longer body, but looking through binoculars you can lose perspective. The muskrat is probably marking the log with its musk or poop. The otter is probably looking for fish remains. Often when feeding her pups, mother otters plaster logs in the water with what's left of the fish she's been chewing. Pups don't start catching fish themselves until well into September when they are five months old.