Monarch Butterfly Migration California 2024 Pdf. The size of this year's eastern monarch butterfly population, which spends winters in mexico, is the second smallest on record, authorities in mexico city said. Monarchs depend on milkweed plants, which are the only food source.

The size of this year’s eastern monarch butterfly population, which spends winters in mexico, is the second smallest on record, authorities in mexico city said. Monarchs depend on milkweed plants, which are the only food source.