Why does monarch butterfly migrate?

One explanation might be that when monarchs march north, they are essentially following the bloom of their primary food source—milkweed plants. And then when winter comes and those plants die back, the animals retreat to a place with conditions that protect them from the weather.

What is the cause of the monarch migration?

Climate change, pesticides put monarch butterflies at risk of extinction. A new study finds that monarch wings are getting larger, possibly because climate change has forced the butterflies to travel longer distances as breeding grounds shift farther north.