Monarch butterflies during migration. Image: Brocken Inaglory / Wikimedia Commons, CC BY-SA.
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Every year, millions of monarch butterflies make one of the most extraordinary journeys in the insect world. Monarchs that live in eastern North America travel south to spend the winter in mountain forests in central Mexico. Some fly thousands of kilometres. The most surprising part is that no single butterfly completes the full round trip. In spring, monarchs begin moving north and lay eggs along the way. New generations continue the journey. Several generations may live for only a few weeks, but the generation born near the end of summer is different. These butterflies can live for many months and travel all the way south to the wintering areas, even though they have never been there before. Scientists believe monarchs use information from the sun and an internal biological clock to help navigate. Their journey depends on healthy habitats and on milkweed, the plant that monarch caterpillars eat. Changes in weather, habitat loss and other pressures can affect monarch numbers. Protecting places where they feed, reproduce and spend winter is therefore important for this remarkable migration to continue.
