Urban beavers making home in Pittsburgh
PITTSBURGH (AP) — A minor ecological setback took a bite out of Western Pennsylvania Conservancy’s plans to plant thousands of native-species trees throughout Pittsburgh. Another native species, beavers, felled a row of recently planted trees at North Shore Riverfront Park in the shadow of Heinz Field.
Pedestrians walking the Three Rivers Heritage Trail noticed the missing trees Tuesday and Wednesday. On the bank of the Ohio River, between the Mr. Rogers statue and Carnegie Science Center, 16 pointed stumps are what’s left of a row of young 4-inch diameter redbud trees planted by Conservancy staff last fall. No tree trunks, no branches. Just distinctive gnaw marks about 16 inches above the ground, a handful of wood chips surrounding each stump and one pair of beaver footprints pressed into the mud near the riverbank.
The culprits weren’t trying to dam the Ohio River. Like muskrats, some beavers live in holes dug into mud banks with one entrance above the water surface and another below.
“I walk by here every day for work but (Tuesday) night was the first time I noticed that all these trees were knocked off,” said Zeb Carbaugh of McCandless. “At first I thought maybe they were cut down, but I took a closer look and it definitely looks like beaver teeth marks.”
Jeffrey Bergman, Western Pennsylvania Conservancy director of community forestry, hadn’t heard about the tree loss until he picked up the phone Wednesday afternoon. He was onsite in a half hour.
“In this location we removed invasive nonnative plant species like bush honeysuckle and Japanese knotweed. We planted native species. Part of the project is beautification, but also to introduce native species to improve the habitat for animals. I didn’t think we’d be quite this successful in improving the habitat for beavers.”
Bergman noticed that the only trees that had been touched were the newly planted native redbuds. The conservancy has worked with the Sports and Exhibition Authority since 2016 to put about 1,800 trees in the ground at North Shore Riverside Park, the South Side, Mt. Washington and the Downtown area. By the end of spring, he said, the Conservancy will have planted some 30,000 trees throughout Allegheny County since 2010.
“Trees have so many benefits,” said Bergman. He glanced back at the row of pointed stumps. “We haven’t lost quite this many (at one time) in the past. Usually it’s one here and one there. But to lose 16 trees out of 1,800 and lose them to a native species? I don’t consider this to be a tragedy.”
Conservancy staff and partner organizations will likely meet soon, he said, to discuss issues including possible riverbank erosion caused by the tree loss.
Growin up to 60 pounds, Castor canadensis is North America’s largest rodent. Extirpated from the Three Rivers as early as 1840, beavers were virtually gone from the state by the end of the 19th century. In 1903 Pennsylvania passed laws protecting the species and in 1917 the Game Commission began importing and transplanting beavers. Today, all Pennsylvania beavers are the progeny of forebears imported from Wisconsin and Canada.
A pair were spotted by runners on the Monongahela River shoreline near East Carson Street about 10 years ago.
“It’s nice there is this comeback,” said Henry Kacprzyk, a biologist at the Pittsburgh Zoo and PPG Aquarium. “It means the rivers are clean enough to support them, even in the center of the city. But they’re not returning to a natural environment.”
Beavers are considered a “keystone species,” said Kacprzyk, because they are one of the few animals that impact every plant and animal around them.
“Their dams back up water creating new aquatic environments and plants, insects, birds and other animals have to adapt,” he said. “Over many years the slow-moving ponds collect silt, which fills in and creates meadows and again everything has to adapt. . It will be interesting to see how beavers do here.”
With few predators of adult beavers, Pennsylvania keeps populations in check though regulated furbearer trapping seasons. Animal control units have been used to relocate problem beavers.
Generally living in monogamous pairs, litters of one to six kits are born in March inside the lodge, traditional or underground. Kits stay for two years sharing the space with their parents and younger siblings.
“In winter when there’s no foliage, they’ll fell trees and push the branches into the mud underwater to save them to use for food,” said Kacprzyk. “You can imagine what it might take to feed a dozen beavers. A beaver family taking out those trees in one or two nights would be consistent with what seems to have happened (on the North Shore).”
Information from: Pittsburgh Post-Gazette, http://www.post-gazette.com