Transcript

DAVID ROBINSON

The monarch butterflies of North America have an astonishing migration as part of their life cycle. The butterflies are found in the United States and southern Canada. But in the autumn, they fly south to overwinter, some in California, but the majority in the mountains of central Mexico, about 3,000 metres above sea level. And the journey to those overwintering sites may be as much as 3,000 miles.

The butterflies cluster on the branches of fir trees and pass the winter in an inactive state. When the spring arrives, the adults become active again, mate, and start the return journey northwards, the females laying eggs on milkweed plants along the way. None will complete the return journey, and it will be their descendants that reach southern Canada again.

Thanks to the work of thousands of citizen scientists who monitor the butterflies every year, more is being learned about the migration. Some volunteers even tag individual butterflies. This week, you'll learn about a number of survey techniques and you'll get to appreciate how you can contribute to scientific research.