Monday, August 16, 2010

Where Have all the Monarchs Gone?

By Susan Thurn,
CNHM Director of Education

Where have all the monarchs gone? Several Museum members have mentioned their concern that they have not been observing monarchs much this summer. Even my own searches have yielded only three caterpillars this entire season. I’ve seen only four or five adults. It is a dismal showing for one of my long-time favorite butterflies.

As adults, monarch butterflies are migratory creatures. They travel great distances each fall to spend winter in temperate climates. Despite the fact that the range of the Monarch’s summer home is quite expansive, the wintering grounds are very limited. Some of these butterflies travel more than 2,900 kilometers to spend winter in places such as Michoacan, Mexico. In the spring, they begin the migration north, lay their eggs, and it is their children that finish the migration to northern Wisconsin. This inter-generational migration is an amazing phenomenon. So why are the numbers of monarchs lower?

In 2002 and 2004, freezing weather in Mexico followed by heavy rains wiped out huge numbers of monarchs during those years, creating a decline in the population. Spring of 2009 brought hotter than normal conditions for monarchs migrating north again, which was followed by the one of the coldest summers since 1928 in much of the breeding area, and finally, poor conditions during the fall migration, resulting in a very small overwintering population This past February, severe hailstorms followed by 15 inches of rain in Mexico are thought to have destroyed as much as 50% of the already declining population.

Added to this problem is the ongoing issue of habitat destruction in the world of monarchs. With an increased use of genetically engineered crops to become herbicide resistant, it has become easier for farmers to spray weed killer, killing any weeds and surviving milkweed while not hurting the crops. Monarchs are also under threat in Mexico due to illegal logging at their overwintering sites.

Scientists believe it will take two or more years for the monarch population to bounce back. Even then, there are still these human factors nature provides that could be a danger to the future of monarchs. Conservation groups are encouraging us all to improve monarch habitats by planting milkweed in our gardens at home, and to encourage schools, farmers, or others with unused land to grow these beautiful perennials. Perhaps with these efforts we can continue to explore and wonder at monarchs from our own back yards.

For over 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and new exhibit, On Lake Owen: The Art of Walter Bohl, in Cable at 13470 County Highway M. Also find us on the web at to learn more about our exhibits and programs. Post your own stories on the Nature Watch blog at

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