One bright, sunny morning in the fall of 2001, I looked out my kitchen window and saw an amazing sight. The blue spruce trees which line the inside of our shelter belt were covered with fluttering, orange and black monarch butterflies.
The humidity was high and the tips of the spruce needles were dripping with morning dew. The thousands of butterflies hung on the branches in clusters like ripe orange grapes. Their wings gently folded and unfolded, warming in the morning sun. By mid morning, their thirst quenched from the dew and their wings dried off from the sun, they began flying around in clouds.
Then they were gone, on their way to their winter homes in the southern United States or Mexico. Because they cannot survive our long cold winters and because the food plants which feed the larva do not grow in the winter, they travel up to 2,500 miles to spend the winter. They are the only insect to migrate such long distances. Each spring, the overwintering Monarchs head back north where they lay eggs on the leaves of milkweed plants. When the caterpillars hatch they eat the leaves, form chrysalises and turn into butterflies. This and the next two generations of butterflies each live about six weeks, repeating the egg laying and metamorphosis. The fourth generation, however, lives six to eight months and migrates back to the same place it’s ancestors spent the winter.
Monarch larva eat only the leaves of milkweed plants. The sap of the milkweed is toxic to many creatures and makes the Monarch a bitter lunch for birds and other creatures who eat butterflies.
Every year, conservationists count the numbers of wintering butterflies to monitor how the species is faring. They don’t count individual butterflies, but they measure the area occupied by overwintering colonies. In the winter of 2001-2002, the year I had migrating Monarchs visit me, the overwintering area, according to Monarchwatch.org, was 23 acres. This winter, the monarch colonies occupy less than 2 acres. That doesn’t surprise me as I saw only two of the butterflies all summer.
Environmentalists and lepidopterists believe that the decline in monarch numbers is due in part to insecticide use in yards, gardens and on farms and the loss of habitat in both breeding and overwintering areas.
Monarch larvae eat only one kind of plant: milkweeds. Milkweeds, a native to the prairies, have almost been eradicated from farmers’ fields and pastures and from roadside ditches. The growing use of glyphosate tolerant crops has all but eliminated the occasional milkweed patch especially in row crops where some would survive cultivation. Livestock producers work hard to eliminate milkweed in the pasture because cattle will not eat it and may become sick if they do. The end of many Conservation Reserve Program acres plowed up many acres of sod which often included patches of milkweed. Some counties weed boards even include milkweed generally or specific species of milkweed in their list of noxious weeds and seek to eradicate them.
Monarchs have historically had ups and downs. Their population numbers depend on many factors like temperature in the spring and summer. Severe weather events, warmer springs and summers and large areas of drought and wild fires affect their survival. Their numbers have recovered from previous lows when bad conditions are followed by good weather. However, their winter populations have not been this low in more than 20 years.
Does it matter? Other species of butterflies have become extinct and life on the planet has continued. Why is this species important? Does the decline in critters like butterflies and moths indicate environmental changes which might affect other species such as birds and bees? Is this an example of unintended consequences of how we approach weed control and food production? Is there a way to have both clean fields and ditches and to leave some place for milkweeds to grow in a controlled way?
My sighting of migrating monarchs in 2001 may have been far more precious than I realized at the time. I’m glad I took pictures.
Copyright © 2014 Janet Jacobson and Sustaining the Northern Plains