The following article was written by Jess Johnsrud, the Education Coordinator at the Woodland Dunes Nature Center.
Monarchs are one of the most recognizable butterfly species with their bold orange and black coloring. Their life cycle is familiar to most of us. They start as an egg, hatch into a caterpillar, then go into a chrysalis (also called a pupa), before the beautiful adult butterfly emerges. What I find most fascinating about the monarch is its migration story. In late August and early September, you may notice large numbers because millions of monarchs are heading south to their wintering grounds in the oyamel fir forests in the mountains of central Mexico.
The monarchs that migrate to Mexico can fly 50-100 miles a day depending on weather conditions. When it’s raining, they cannot fly because their wings get too heavy from the water. On rainy days, they will hunker down in a quiet, dry spot until the rain passes. Monarchs also cannot fly as far or efficiently when they have to fight against the wind. Warm days with a strong wind that pushes them south is ideal. They do not migrate at night, but roost or cling to branches of trees. Monarchs feed on nectar from flowers all along their route to Mexico in order to store much needed energy.
The flight to Mexico typically takes six to eight weeks. Once in the mountains, they roost in the oyamel trees at almost 10,000 feet above sea level. Millions of monarchs will cluster together on the trees, covering the branches and even weighing them down. They cluster together to stay warm and for protection from predators like the Black-headed Grosbeak and the Black-backed Orioles.
While they are roosting in the trees, they conserve their energy by going into a state of temporary dormancy. The monarchs live off fat reserves from all the nectar consumed before and during their migration. Amazingly, they gain weight during their migration to Mexico.
In late February and March, the monarchs leave their winter grounds and start the trip north. During this time, they prioritize travel over feeding and often fly at higher altitudes when the wind is favorable. The highest recorded monarch was seen at 11,000 feet by a pilot!
Once they reach southern states such as Texas or Oklahoma, they mate, lay eggs, and pass away. The caterpillars that hatch from these eggs grow into the first generation of monarchs for that year. These adult monarchs only live about four to six weeks, but continue to move north before mating, laying eggs, and passing on. The second and third generations make their way north during the spring and summer months. The monarchs that emerge in late summer are usually generation four or five and this is the long-lived generation that migrates to Mexico for the winter.
Much of what is known about monarch migration is through decades of monarch tagging from both scientists and everyday citizens. Monarch tagging involves putting a small sticker with a unique number on a specific part of the hindwing of the generation that migrates. This doesn’t impact the monarch’s ability to fly, but it does allow humans to learn where they go. If a tagged monarch is found deceased, the number on the sticker is reported to Monarch Watch. This is a nonprofit that educates, conserves, and researches monarch butterflies out of the University of Kansas. Researchers can then find out where the butterfly was tagged and how long it lived.
Labor Day weekend and the week after are often peak times for monarch migration in Two Rivers. Good places to look include the gardens along the Mariner’s Trail, fields with native flowers, and the Woodland Dunes’ butterfly garden. I hope you witness the monarch’s incredible fall migration.
