how to stop rodents from eating my cactus??

I live in the high desert of southern California. Two weeks ago, I put in a small cactus garden with red yucca, dollar prickly pear and mission cactus. My problem is the indigenous kangaroo rats. They've decided that the mission cactus is a tasty treat. Is there something I can do to discourage them from feasting without harming them or the plants?
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