How do monarch caterpillars use milkweed chemicals to defend themselves?

Monarch caterpillars utilize the chemical defenses of milkweed plants to protect themselves from predators through a process of sequestration. Milkweed produces acrid, milky juices containing toxic compounds known as cardenolides, or cardiac glycosides.123

While these substances are highly poisonous to many vertebrates—often causing vomiting or heart failure—monarch larvae are able to consume the plant without suffering ill effects. As the caterpillars feed, they store these toxins within their bodies. This chemical protection is retained through the pupal stage and into adulthood, rendering both the caterpillar and the butterfly distasteful to potential predators, such as birds. By incorporating these plant-derived poisons, monarchs gain a significant survival advantage, as predators that sample them learn to avoid them in the future.2413