Over the past few weeks we’ve been noticing a lot of activity in the air. The dragonflies are flitting around our farm again as are the Yellow Swallowtail butterflies and a whole host of butterflies, bees and other flying creatures. Yet, we still haven’t spotted any monarch butterflies this year. Over the past 20 years the overwintering monarch populations have dropped by 90%, bringing a sense of
urgency to the reality that this species may become extinct one day very soon if we do not rapidly change the course of events. Common Sense Pest Control Quarterly is a publication of The Bio-Integral Resource Center, a non-profit that provides practical information about the least toxic methods of pest management. In their May 2016 publication, William Quarles, Ph.D., provided us with some very interesting information about the monarch butterflies. We would like to share some of these facts with you that make this creature all that more amazing to us.
Monarch butterflies are actually a prehistoric creature thought to have evolved about 100 million years ago! They are thought to have become migratory creatures about one million years ago. There
are now two populations of migrating monarchs, one population east of the Rocky Mountains and the other on the west side of the Rockies. In order to survive, monarchs need water, nectar, milkweed and trees on which to overwinter. The rapid decline in their populations is directly related to human behavior and specifically to the drastic increase in use of pesticides over the past two decades. In
addition to causing death through direct contact with pesticides, the use of glyphosate and neonicotinoids has destroyed a significant amount of milkweed as well as causing death of monarch larvae and reductions in plants that provide nectar for the butterflies. Milkweed is an important plant for monarch survival and is one of the main reasons monarchs migrate to the north during the spring and summer from their southern overwintering site in Mexico. Milkweed contains steroids called cardenolides which monarchs ingest. This component of milkweed protects monarchs from predators by giving them a bad taste as well as being toxic to vertebrates. Milkweed is a food source for monarch caterpillars as well as serving as a nectar source for the adult monarch butterflies. Additionally, monarch females lay their eggs on the underside of milkweed leaves.
The migratory pattern of the monarch population east of the Rocky Mountains takes the monarchs to northern climates in the spring and summer in search of milkweed. Monarch larvae development stops at 52-54°F. In addition to decreasing temperatures, their milkweed sources cease in the fall and winter thus they migrate to their overwintering site in Mexico to wait out the winter. They start to migrate south about mid-September and move at a rate of about 20-25 miles/day. During their migration they focus all of their energy on moving and stop mating and producing eggs. They feed aggressively to gain fuel for the flight as well as build up fat deposits for overwintering. Just where does a slim creature like a monarch deposit fat? When they reach their overwintering spot in Mexico, they’ll huddle together in clusters in trees to stay warm until spring arrives. In the spring they start their vigorous mating ritual, then fly north into Texas and the southern parts of the U.S. to lay their eggs on milkweed. These eggs hatch a spring generation that then flies further north in order to get away from the heat of the southern summer. Once they arrive in the north they produce 2 or 3 summer generations, the last of which will migrate south in the fall. The generation that will overwinter has a lifespan of about 8-9 months while the spring and summer generations only last about 3-5 weeks.
So how can we help support the monarch populations and prevent further decline? One way is to provide more milkweed for the monarchs. One of the plants in our pollinator packs was Asclepias tuberosa, a type of milkweed commonly known as butterfly weed. There are also efforts being made by various environmental groups to create Monarch Way Stations, plantings of milkweed in the migratory path of the monarchs. Additionally, planting flowering plants to provide a source of nectar will help provide them with the fuel they need for their flight. While these efforts are all positive, we must remember that their benefit is limited if there is still use of pesticides and herbicides on the
plants or in their vicinity where they will be affected by drift. We have been planting native flowering plants and milkweed on our farm for many years. We’re excited to see how many people chose to participate in planting the pollinator packs we delivered over the past several weeks. Now many of you are creating your own Monarch Way Stations in the Twin Cities, Madison and our local area. Please let us know how your gardens are growing and what critters they are attracting.
Dr. Quarles concludes his article with this statement: “Monarch butterflies survived the dinosaurs and have probably been migrating for a million years. We should not let pesticide pollution and human activity destroy them. Working together, we can bring back the monarchs.” Let’s all do our part.