I have a barn cat that steals my ermine out of my rat traps.

Any ideas how to keep the cat out but allow the ermine to still get caught?

A longer weasel box might work. Make it so the cat can't reach the weasel. Then again you might try catching the barn cat first.

Use a 1.75 - 2" restricted entrance hole on a long box with deep trap spring slots like this mink box:

Thanks guys.

I might try an extension off the front vs rebuilding longer. Do you think that would create refussals? I really don't want to rebuild the boxes, price of lumber is still ridiculous.

The cat is mine, don't want to catch her. She does her job keeping mice at Bay. She is a pain in the rear on my trapline, follows me like a dog and gets into everything.

Have you tried fully enclosed boxes with a 2 inch entrance hole using rat snap traps in them. Pretty reasonable set up.

Weasels a better mouse catchers than cats so if you want to get rid of the mice, why are you going after the weasle?

My boxes are enclosed with a 2" hole. I set the trap so they step on the pan soon as they enter the hole. The back half of the weasel is outside of the box. I'm surprised the cat could pull the weasel out of the trap but it happened.

I have chickens so I try to keep the population of anything that might kill them in check. If not for the chickens I wouldn't target weasels because I can't stand mice in my pole barn.

Shoot the cat

I used to feel this way until someone dropped this one off a few days before Thanksgiving last year. It was just a kitten at the time.

Put a sardine in your weasel box and let the cat get snapped a couple times. It'll quit going in them once it associates the box with getting it's paw snapped