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.
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The Ultimate Bucket Mouse Trap - by Budget101
If you have a large infestation of mice, here's the ultimate bucket mousetrap, the most effective homemade mouse trap. This bucket mouse trap can be used
