David Voigts.

One of the anticipated events of spring is the arrival of migrating monarch butterflies, but in recent years their number has declined greatly. Much of this loss has been caused by a great reduction in the abundance of milkweeds, the required food of monarch larvae, as a result of intensive farming practices. However, the warming climate also plays an increasingly important role.

It has been shown that very warm spring temperatures, such as those experienced recently in the southwestern states, will kill monarch larvae. In one study, temperatures above 97 degrees caused significant larval mortality and temperatures above 84 degrees led to developmental delays, resulting in decreased adult body mass and a less likely chance of survival.

Temperature also triggers the start and speed of monarch migration, and warm temperatures can cause a mismatch between monarchs and their milkweed host plants. This has led to limited reproduction. In addition, hot and/or dry conditions can reduce the quality of milkweeds as food for larvae.

With all these threats to monarchs, it is important to do what we can to help them survive. Even a backyard waystation of milkweeds for larvae and nectar producing plants to provide food for migrating adults will help.

David Voigts is a retired ecologist and the current Conservation Chair for the Prairie Rapids Audubon Society. He is a Tama County native, graduating from Dinsdale High School, and lives in rural Jesup on his wife’s family farm.