Excerpted by permission of the publisher, Pelee Portrait, Canada’s Southern Treasure
For a few special days each autumn, Point Pelee is a temporary home to countless thousands of migrating Monarch butterflies. Although commonly observed roosting in trees in times of cold weather – warm weather can preempt a stop-over altogether – the Monarchs are never in the habit of lingering. Once favourable conditions present themselves – warmer temperatures and supportive winds – they forge on across Lake Erie toward their destination in the mountains of central Mexico some 3,000 kilometres [1,800 miles] away. The Pelee peninsula offers the shortest route across the lake. Point Pelee’s shape funnels the Monarchs to its tip.
Why such a marathon journey for this insect? The answer lies in the Monarch’s food plant. Milkweed is the only plant that that Monarch caterpillars eat. It is believed that milkweed and Monarchs evolved in the mountains of Mexico. As the milkweed adapted and its range extended, the Monarch followed. But milkweed is listed as a noxious weed in Ontario and many states, posing a serious threat to the butterfly. As milkweed plants are removed, so is the Monarch’s only food source. If milkweed disappears, so will the Monarch.
At present, the Monarch migration cycle remains a mystery. Through the summer there are two or three generations of the butterfly raised in Ontario. From egg to adult only takes about a month. The generation that emerges in the late summer is somehow triggered to become a migratory generation. This generation over-winters in Mexico and mates there in the early Spring. On their way north, eggs are laid on fresh milkweed and the adult dies shortly thereafter. It may take several generations of Monarch offspring before northward-bound butterflies reach Canada in May. No Monarch makes the entire journey. The mystery lies in how they know where to go.