During the Museum group’s visit to El Rosario Monarch Butterfly Preserve, our guide Daniel called me over to an educational display he’d laid out on a stump. Each of the three butterflies had been eaten by a different predator, and their bodies bore tell-tale clues.

Each of these predators—the mice, the grosbeaks, and the orioles—have something in common with the monarchs themselves: they can ingest milkweed toxins and survive.