M2. Monarch migration
Background
The North American monarch migration is considered one of the most spectacular natural phenomenon in the world. After going through this unit, you will understand why!
Task
There are three main populations (large groups) of monarch butterflies in North America. Each one lives in a separate geographical area, and each one migrates south to a different place. There are two populations that live partly in Canada. The other population lives much further south.
Look at the three main monarch populations on this map:
Migration of the Eastern Monarch Population
The Eastern monarch population is the largest in Canada by far, making up over 90 per cent of Canada’s monarch population. They also have the longest migration, at up to 4,500 km.
Migrating South
Around late summer or early fall, when temperatures dip and daylight hours lessen, monarch butterflies know it is time to head south.
Monarchs are solitary (they live alone), but during migration, they cluster together in great numbers in roosting areas. As the Eastern population begins the journey south, they gather in areas like Point Pelee National Park, on the shores of Lake Erie, and in Presqu’ile Provincial Park. These groups of migrating monarchs can contain from a few hundred to thousands of butterflies. They roost overnight before traveling along Lake Ontario and Lake Eerie.
They continue their journey South until they reach their overwintering grounds. The eastern monarch population reaches Central Mexico in November and December. They form dense clusters on the trees of the Oyamel fir forests, where they stay inactive for the next few months.
Does this look familiar? It should! These overwintering monarchs should resemble the monarchs you coloured and posted in module one.
Migrating North
In March and April the monarchs begin their journey back north. They follow a migration path that includes of a series of breeding sites that are rich in milkweed.
Monarchs use these sites along the way to lay their eggs before they die. The new eggs eventually grow into adult butterflies, as you’ve learned in the life cycle module. These new butterflies continue the migration north. This cycle can repeat itself up to five times before the monarchs make it back to Canada in June and July!
Two-way Migration Summary
The two-way monarch migration can be tricky to understand. Try thinking of just one Eastern monarch on its migration. It goes like this: One monarch migrates all the way south, overwinters and begins the journey back north. It will travel a bit until it stops to lay eggs on milkweed. This long-lived butterfly (they live for six to nine months) will die soon but her eggs hatch and become butterflies themselves. These new short-lived butterflies (they live for about one month) continue the journey back home. This cycle repeats itself, up to five times, until the monarchs return to the United States and Canada where they spend their summers.
Learning Objectives
Understand the monarch butterfly migration process.
Continue to M1A. Draw a wild space for monarchs »
