Little River Wetlands Project staff and volunteers are doing what they can to help monarch butterflies thrive.
The showy orange-and-black insects, which migrate south each fall to spend the winter in Mexico, face many threats in the wild and have experienced population declines.
To learn more about monarchs and to help them, about 20 to 25 Little River Wetlands Project volunteers each recently began walking a trail weekly to a specific site in the organization's Eagle Marsh, Arrowhead Prairie and Arrowhead Marsh nature preserves, said Dani Bradtmiller, outgoing preserves and programs assistant director. At their site, each volunteer checks milkweed plants for monarch butterfly eggs and caterpillars and counts any that are found.
While adult monarch butterflies feed on nectar from a variety of flowers, their caterpillars eat only the leaves of milkweed plants.
The volunteers also will be looking for chrysalises, the cases in which caterpillars go through metamorphosis into butterflies, Bradtmiller said.
The volunteers then report their findings to a fellow volunteer, who sends the information to the Monarch Larva Monitoring Project (MLMP) based at the University of Minnesota in St. Paul, she said. The local monitoring will go on through at least mid-September.
Volunteers with Little River Wetlands Project proposed participating in the monitoring project and have been doing the checks each summer since 2013 at Eagle Marsh, Bradtmiller said. Last year, she had enough volunteers to expand the monitoring work to Arrowhead Marsh and Arrowhead Prairie, which Little River Wetlands Project also owns and manages.
The data they have collected in past years showed steady growth in numbers of monarch eggs and caterpillars found from 2013 through 2015, but a big drop in both last year. Bradtmiller believes the decline last year resulted from monarchs being hit by an ice and wind storm as they began their migration north from Mexico.
Along with helping with the national study, participation in the MLMP also allows Little River Wetlands Project to see how its monarch egg and caterpillar numbers compare with other areas around the country, Bradtmiller said. In addition, the project trains volunteers to do real science, and the research provides insight into the health of insect pollinators in this area and what needs to be done to help them, she said.
One thing researchers have learned is that monarchs, which feed on flower nectar, do better with a diverse mix of flowering plants rather than a high density of a few types of plants, she said.
In a related MLMP project, Little River Wetlands staff and a few volunteers also are preparing to do an annual milkweed density study on the organization's nature preserves, Bradtmiller said.
Using a square made of PVC pipe that measures 1 meter — about 3.28 feet — per side, study participants set out in a straight line and lay the square down on the ground at a set interval of walking steps, such as every five steps, Bradtmiller said. The person records the number of milkweed plants found in the square and then moves on by the set number of steps to lay down the square at the next sampling location.
The process continues across the nature preserve.
The sampling process provides an estimate of the number of milkweed plants in each nature preserve in relation to the acreage, Bradtmiller said. Little River Wetlands Project conducts the milkweed density study once a year. This year, they hope to do it in late July or early August.
Study results also will be forwarded to the MLMP, which is located on the Web at monarchlab.org/mlmp.