Monarch Butterflies Are Special

Across the Fence #510

The Monarch butterfly is probably the most recognized of all our butterflies. Who among you can raise your hand and say you’ve never seen one? Not many of you, but the day may come when very few hands will be raised. Monarch sightings are getting fewer all the time.

We’ve always had a lot of monarchs around our place. Milkweed plants are plentiful along the fenceline behind our house. I try to protect them. I’d hate to see the day when that fenceline and all the natural habitat that goes down the lane alongside the fence is destroyed. Milkweed plants are essential for the life cycle of the monarch butterfly. I think that’s why we still see a lot of them when many people say they’ve only seen one or two all year.

Most people don’t give much thought to the extraordinary life cycle of the monarch. Ever since I first learned that those little fella’s fly up to three thousand miles south to spend the winter in central Mexico, I knew there was something special about them. At the Mexico wintering sites, the butterflies roost in the Oyamel trees, a species of evergreen. They form large communities numbering in the millions of individuals. Illegal logging of those trees in Mexico is destroying much of their habitat and in 2012-13 a survey showed a 92% decrease in the monarch population when compared with the 1996-97 count. That’s alarming.

I’ve always found them fascinating and wondered how those little butterflies find their way from Wisconsin, Iowa, and Minnesota, all the way to central Mexico. Most of us humans would have to be equipped with maps and GPS devices to find our way and then we’d probably get lost. The other thing to consider is that the butterflies doing the migrating have never flown that route before. They aren’t the same ones that migrated north in the spring. Since the normal lifespan of a monarch is two months or less, those butterflies are long gone. However, the last generation of the summer that heads south can live for seven months or more. Scientists now think flight navigational patterns are inherited, and based on a sun compass that uses the earth’s magnetic field for orientation. Those are pretty sophisticated navigational instruments for a little butterfly. We need to give them more respect.

Monarch Caterpillar eating on a milkweed plant.

The overwintering monarch’s mate in the spring in Mexico prior to migration. The eggs are laid on the leaves of milkweed plants. After four days the larvae (caterpillars) hatch. They feed on the milkweed and store a type of cardiac glycoside, that becomes their protection against predators. The caterpillar stage lasts about two weeks. The caterpillar then spins a silk pad on a twig or leaf. I know many of you have seen those green cocoons. The caterpillar lives in this for another two weeks while it goes through a transformation and emerges as a monarch butterfly. There’s also a summer breeding period while they are here in the north country. I came across a mating period a couple years ago when I saw dozens of monarchs flying around in the field near the fenceline behind our house. I grabbed my camera and went closer to get some photos. I watched as they chased each other around until the male would make contact with a female and they would eventually fall to the ground. This is where the mating took place. They were then so preoccupied I could get right next to them to take photos. 

The offspring from that mating frenzy would be the monarchs that migrated to Mexico in the fall. Once again, it’s such a marvel when you think of them finding their way. Several generations later, a new batch will find their way back to us next summer.

I mentioned earlier about the caterpillar feeding on the milkweed plants and ingesting cardiac glycoside. This substance gives the monarch a foul taste and they are poisonous to birds and other predators. When they see those bright yellow and orange colored butterflies, they know they need to avoid them.

Unfortunately, the monarch’s still have a lethal enemy… it’s us. Man has become their biggest enemy. The yearly decrease in their population has been linked to the decrease of the milkweed plant that provides their primary food source. The use of herbicides to control weeds in their reproductive and feeding areas, has destroyed much of this food source. Also, the removal of fencelines in order to make bigger fields, destroys the brush and habitat where the fences were. The mowing of brush and plants along roadsides has also destroyed much of their food source and habitat.

Unfortunately, this is what has happened to hundreds of milkweed plants that were in the ditches along our country roads. All mowed down and the monarch's food source destroyed.

Is it any wonder that people are seeing very few monarch butterflies in their areas these days? We’re lucky to still have some around us, but how long will it be before they become scarce here too? Perhaps someday, future generations will have to visit a zoo to see monarch butterflies in a zoo environment, or go to a natural history museum to view another extinct species, like the passenger pigeon, that once numbered in the millions. We can still save the monarch butterfly by not destroying all of it’s habitat and food source. My hope is that people are willing to do that?

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