I saw my first river otter today, 3 of them while out on the rock river near Sterling IL. It was cool seeing the otters, I thought I was seeing something strange running down the bank last time out, looked way too big for a ground hog. I think I know where their den is. I bet they eat a lot of fish, but that only makes up a portion of their diet. They also eat snakes, frogs, crayfish and weeds. They can stay underwater for about 8 minutes and swim quite fast and they cover a lot of water. I was seeing them off and on in a mile stretch. I think I found their de, a large mound on the bank with lots of holes and there was a couple places where they had been sliding down the bank it looked like.