Wildlife Watching Wednesday: Monarch Butterflies in Peril
By: Tom Berg
Monarch Butterflies are one of the joys of summer. These beautiful orange and black butterflies are known as “milkweed butterflies”, which simply means their larvae only eat the leaves of milkweed plants. However, the common monarch is not as common as it was a decade or two ago. Extensive use of weed control herbicides by farmers in recent years has drastically reduced the amount of milkweed plants nationwide, and the monarch population has suffered because of it.
Happily, monarchs are still around and they find enough milkweed plants to survive (barely). Milkweed gets its name from the thick milky white sap that appears wherever the plant is cut or damaged. One surprising fact about milkweed is that it contains high levels of toxic cardiac glycosides, making the monarch caterpillars and adult butterflies very poisonous. Luckily, the toxins do not affect the monarchs. It only affects predators like birds and mammals that try to eat them!
Adult monarch butterflies in the USA take part in annual long-distance migrations, so they can over-winter in warmer climates. Monarchs living east of the Rocky Mountains migrate south thousands of miles to Mexico. Western populations migrate to central and southern California.
Surprisingly, the migrations exceed the lifespan of most individual monarch butterflies, so it takes three or four generations (or more) to travel to the over-wintering sites and get back north in the spring and summer. During their migrations, adults eat nectar from a variety of flowering plants, including goldenrod, thistle, milkweed, alfalfa and others. But of course, the caterpillars will only eat the leaves of milkweed plants.
Gardeners and conservationists can help the monarchs by planting milkweed seeds in their own flower gardens at home and in public gardens (where allowed). Milkweed plants feature large, aromatic flower clusters in late spring and early summer, and the flowers attract monarchs and other butterflies. The adult monarchs lay their eggs on the milkweed leaves and the cycle continues.
Watch for the beautiful monarchs this summer and cultivate a few milkweed plants of your own!
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