Butterflies love living on the edge


UNIVERSITY PARK, Pa. – Living life on the edge is not a good thing for human beings, but it’s apparently healthy for butterflies.

A scientist in Penn State’s College of Agricultural Sciences said vegetative areas on the edges of forests and farmland provide ideal habitat for butterfly communities.

“I found that butterflies can thrive along the edges of forest logging roads, within power line rights-of-way and along the edges of farmlands and other agricultural lands,” said Richard Yahner, wildlife conservationist.

“By taking a few simple steps, farmers and forest managers can help these communities maintain themselves.”

Habitat use. Yahner completed a research project, funded by the Wild Resource Conservation Fund and the Pennsylvania Agricultural Experiment Station, designed to determine how butterflies use different Pennsylvania habitats – managed forests, agricultural lands, and residential areas.

“When I started this research project I thought there were three types of butterflies – yellow, orange and black,” he said. “I never imagined I’d see 30 different butterfly species in a single habitat.”

Yahner suggests several methods for cultivating butterfly populations. Farmers can maintain a strip of wild herbaceous vegetation 12 to 15 feet wide along field edges. Grazing animals should be kept from pasture edges.

“Farmers often don’t plant right up to the edge of a field, using that edge as a way to get equipment in and out,” Yahner said. “By leaving edges wild, butterfly communities can establish themselves.”

A crucial role. Forest managers and rural road supervisors should delay mowing road edges until late September, after the growing season has wound down.

“Various butterfly species will use edge habitats for a short time,” Yahner explained. “If road edges are mowed in June, this will not only destroy habitat for butterflies that may use it then, but also for other species that may use the same area later in the summer.”

Yahner said maintaining butterfly habitat is particularly important because butterflies, which are active pollinators, play a crucial role in establishing wildflowers each growing season.

Rarely seen. Yahner’s research also revealed that many butterfly species that inhabit forest edge habitats are rarely seen in more cultivated areas, such as farmland or urban areas.

“If you visit a forested area at the right time, you’ll see butterfly species you never dreamed were here,” Yahner said. “Humans aren’t aware of them because few people spend enough time in the woods to see them.”

The butterflies most people see – monarchs, swallowtails and the familiar cabbage white – tend to inhabit areas near farmland or developments. Yahner pointed out that butterflies common to farmland habitat are often non-native species, also called “exotics.”

“Native species are much more likely to live in forested areas,” Yahner said. “The exotic species are adaptable to more types of habitat, but they are most often found near farmland or other, more urban sites.”

Domino effect. Yahner said maintaining butterfly habitat in farm and forested areas is important because the health and abundance of butterfly communities can have a domino effect on the biodiversity of a particular habitat.

“Wildflowers are dependent on butterflies for pollination, so a decline in butterflies can mean a decline in wildflowers,” he said.

“Because butterflies or their caterpillars also are a food source for animals, birds and other species can be affected if butterfly populations decline.

“If vegetation along logging roads or along farmland edges can be maintained through the growing season without mowing or spraying, butterfly populations can maintain themselves,” Yahner explained.

“If that habitat is taken away, the butterflies are gone as well, which in turn lessens the diversity of that area. If that sort of practice keeps occurring or expands, then Pennsylvania might lose some of its butterfly species.”

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