Fluttering monarch butterflies were a common sight at Lebanon Hills Regional Park this summer. For the third year in a row, Dakota County Parks staff raised wild-caught monarch caterpillars and released the adult butterflies in an effort to collect data for migration research and to help stem the species' population decline.
This summer, 51 monarchs were released in Lebanon Hills from the park's indoor rearing operation. Of those, 33 were tagged as part a migration study by the University of Kansas. The university's Monarch Watch citizen science tagging program seeks to better understand mysteries of the monarch migration and habitat needs. Once they are ready to fly, each butterfly is given a small sticker tag with a unique number. The tag goes on the outside of the hind wing and does not impede flight. If found or recaptured, the number is reported to Monarch Watch.
To date more than 1.5 million butterflies have been tagged with more than 13,000 recovered.
A 2016 study showed the monarch butterfly population has declined 68 percent over the past 22 years, due in most part to habitat loss and climate change. Here on the summer breeding grounds, monarch eggs and young caterpillars are at risk of being eaten by numerous insects and arachnids. Another potential danger is ending up in a milkweed desert. If there are only a few milkweed plants available for females to lay eggs on in a given area, those few plants can end up hosting many more caterpillars than they can feed. When staff found caterpillars in danger from either predation or lack of food resources, the caterpillars were brought inside to be reared to adults.
Caterpillars were reared in different enclosures according to size as they go through five molts in the caterpillar stage called instars. This allowed staff to better monitor milkweed consumption and watch for any bacterial or parasitic infections. It was a group effort at the Visitor Center finding food, cleaning containers, checking and sorting caterpillars, and tagging and releasing adults.
The public had opportunities throughout the season to learn about the monarch program, and some participated in butterfly tagging. Dakota County Parks plans to continue the monarch program in 2019 and is expanding pollinator and monarch butterfly habitat at the Lebanon Hills Visitor Center, including through volunteer work at the Sept. 29 Nurture Nature event in recognition of National Public Lands Day.