Put out some mink boxes with coni pan 110's and baited with a muskrat leg wired to the trap. Check them out two days later and just a leg bone with very little meat on it. Trap is still set. Is this mice ? Can anything be done to prevent it ? Also I had some DP's along a creek bank that were getting cleaned out every day . Tried using mini marshmallows, fish pellets, etc. even put a golf ball sized rock on top, still completely empty the next morning. No coon tracks in the mud or sand around the trap, so what's doing this ? It's driving me crazy ! Thanks

weasels

Mice

Sounds like mice to me.

I had weasel trouble trapping marten in boxes with 120's. Those pans solved it. The ermine got pelted also. I didn't have my bait fastened to the trap. It was in the box behind the trap. The back of the box had hail screen on it. I think on the ground for mink it would work the same way. You might want a trap on each end of the box. Field mice might not be heavy enough to fire the trap . Same with birds. If they do there is a good chance the trap wont hit them. If it turns out to be mice some wooden mouse traps baited with peanut butter might keep them out and provide you with some good bait for those mink or coyotes or fox or bobcats or coons......

Mice,voles,and shrews will consume a small piece of bait in a short time.
Use a larger piece of bait in your box,almost fill the box(not so much that it will affect the firing of the trap) this way the animal will be positioned for a good strike,and there will be lots of small mammal activity working the larger piece of bait,which is more of an attraction than the bait alone.
Make your 120 boxes 14 or 16 inches deep with 1\2 inch screen on the back.
Always check your bait once a week.

In my country,that would be deer mice.They will strip a half a muskrat carcass in a week or less.Boco is right on.Once a week is about right,to replenish bait.I have ben meaning to try the 1/2" mesh.I use the same boxes in the forest,for spotted skunks and have the same problem.

Wrap bait in steel screen or a wire mesh hardware cloth

I would say mice or shrews.

I had nice take the bait out of 3 of my pipe dream sets for coyote. Couldn't figure out why they hadn't connected yet. They were in very good location with lots of sign. The pipes were empty that is why. I may not have known what happened but with the snow there was a nice mouse hole right to the top of the pipe. Thinking of using a smaller diameter pipe to prevent this.

You are located in Indiana, correct? Any farmland nearby? Any No-till farming going on? Like the previous posts stated - mice, voles and shrews. And if its no-till farm country these animal populations have exploded in the last 10-15 years due to the reduction in tillage. No farm disc burying them, their homes/holes, or their litters so they don't need grassy areas to raise a family and sustain a living,,, a corn-bean or hayfield provides all they need. As a side note; our badger population has increased in response to no-till farming also (with the prey comes the predator --- Bio 101). Bob's advice of the 1/4" hail screen (better than 1/2") wrapped or boxed around your bait will keep the little critters from devouring it in your cubby................... my take