Hi-

There is a possibility of catching three species of weasel (long-tailed, short-tailed, and least) in the areas I trap. Will a weasel box with an entrance hole of 1 3/8 inches work for all three? Thanks.

2" seems to be the magic number

2"
http://www.trapperman.com/trapperman/The_Weasel_Box_Set.html

https://trapperman.com/forum/ubbthreads.php/topics/1667609/Weasel_-_NEED_WEASEL_BOX_PLANS

I used a 1 3/4 bole because I couldn't find my 2 " at the time. Works great on short tails around my area.

All mine are 2-1/8" dia. I happen to have a door knob bit laying around. But I have only caught shorttails in my weasel boxes... oh! and a zillion mice, so I'm probably good to go on least weasels too!

IMO 1 3/8 inch hole is a bit small, even for large short tail weasels. I would go with 1 3/4 minimum size .

With a 2 inch hole a mink can get their head in it. That is where a 1.5 LS works better than a snap type trap. You catch them right by the ears!

Thanks ,folks. I may end up buying some boxes, and then using a hole saw to enlarge the existing hole to 1 /34 - 2".