Ok,, they are out of season here but talked to the CO and if they are doing damage you can trap them because they are considered a nuisance animal. Nephew bought a place with a pond and the lady he got it from said it had a muskrat problem and he asked me to get rid of them to keep the yard from caving in.

The moss is growing already and the runs look unused and there is no fresh sign at all. They have eaten all the roots off the cattails and the leaves are laying on top of the water so there must have been a ton here in the fall and winter.

There is a bigger pond about 100 yards away with not much vegetation around it and a large creek about 80 yards in the other direction. I also found water wolf scat beside the pond. Would the otter have killed all the rats or did they just leave? Or was there to many and they got sick and died?

They will come back, I have seen this be for.

Did they just move somewhere else until the cattails grow fresh again or something?

Most situations I have seen with a heavy population and then a quick die off are the result of disease, probably tularemia.

This is one of the reasons I hate nuisance trapping muskrats. Unless the owner called and said he saw a muskrat 5 minutes ago, you're chasing ghost animals. At least in my area.

Could be a combination of things. Moved to creek or just coming over feeding and leaving. I trap a couple of ponds locally. There is a third pond that I don't trap close by, I'm talking maybe 100ft. It's feeding rats into the ponds I trap.

Trapped out in the fall?

Not trapped at all.

More like they saw one and tell you they saw a dozen......

There was lots of dens and tons of cattails with the roots chewed off. I have trapped long enough to know muskrat sign. But it is from fall and winter and now nothing fresh, moss in the bottom of the runs that would have been swept out from even one rat. Looks like there was a lot, so maybe they got the rat plague and died.

Hard to tell. Maybe they moved around based on the season.

I wondered if they ate all the good food and left.

That could be a possibility. Do you have access to the pond that is close to see if they are there. I'd also check creek. If you find them there possible next season trapping?

Different owner for the big pond, have not looked, I am pretty sure I could get permission to trap it. I can trap the creek, to much rain to check the creek right now. Not a big deal, he just wanted them out of the pond. The new owner might kill all the cattails and if there is no food the rats might not come back

Being there were "tons" of rats in the fall, no trapping and now no rats I still say disease. Although you state they have eaten all the roots of the cattails, rats eat a great variety of foods. These foods include water lilies, cattails, sedges, wild rice, clover, switch grass, arrowhead, frogs, fish, crayfish, snails and mussels.