It's not exactly humane, but water bucket traps can be as effective as poison and much better for the environment and good predators. They are easy to make. One fellow reported trapping 20 mice in one night. You can buy them as kits, but they are easy to DIY. There are many variations on the basic idea. This is a simple version.
The Ultimate Bucket Mouse Trap
The Ultimate Bucket mouse trap- This effective homemade mouse trap can be used with water to kill off large infestations or without for a humane live trap
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