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Wissahickon’s study pits man against Angora goats

For the next couple of months, it will be man against beast on the Cresheim Creek in the Wissahickon.

Working separately ― one group (six  to ten human volunteers) with strong hands, the other (six Angora goats) with determined chompers ― the shared goal is to combat a common enemy: invasive plant species.

The project is part of the park system’s attempt to seek alternatives to its most frequently used method of weed control — pesticides like Roundup.

Using six test sites — two for each of the three methods – that are situated in close proximity and covered with the targeted plant species, the park will conduct the tests through the summer and early Fall.

After each visit by man, goat, or applied weed killer, a botanist will return to identify the remaining species and their quantity. The second goat test occurred earlier today, with a third one scheduled for later in the growing season.

So, far, the humans are winning ― but that’s not the point, according to Maura McCarthy, executive director of Friends of the Wissahickon. “I’m guessing we’ll find that there’s no one answer to solving all of our land management problems,” she says. “The real idea is to highlight the issue of why we should care about invasive species in the first place. They’re slowly edging out native species, and because they can have a real effect on everything from erosion to our drinking water.”

The Friends group is conducting the test in response to the oft-asked question of why the park seems to favor herbicides. “The answer is because in some locations we have acres of species like knotweed, or acres of particularly pernicious species like bamboo, and hand-weeding just wouldn’t work,” says McCarthy. “But that doesn’t make it any easier for people, including myself, to accept. So for us, the goats are an experiment to see if they work better than pesticides for certain species or in certain areas like on hillsides or near water.”

Enter the goats. One advantage is that the creatures positively relish a meal of poison ivy ― a species no human weeder wants to tangle with, says Yvonne Post, a New Jersey farmer who is providing the cadre of six wethered (castrated) goats.

More importantly, she adds, their very presence may act as a deterrent to future unwanted growth. “If you have a natural predator toward the plants, they will ‘learn’ to stay away.”

Plus, goats eat vertically and their tug-and-pull munching better interrupts root growth.

Unlike humans, the goats also attack the berries and seeds of the plants, further inhibiting future repopulation.

Post, whose relatively small goats have also been turned loose on patches of Bartram’s Garden  and Swarthmore College’s Scott Arboretum, has kept her team to just six for practical purposes. “If the park decided to go forward with greater herds and greater swaths of land, they would use many more goats, and they’d be Boer goats, which are about twice the size at 90 pounds, and have voracious appetites,” she adds.

In that case, the Friends would likely look to partner with a closer-by university or larger farm, says McCarthy.

Whatever the outcome of the tests, one thing’s for sure: the roving ruminants are not without their own downsides. “The first day I took my goats to the Wissahickon,” Post says, “there was a loose dog nearby and that set the goats back a good hour or so!

“Generally,” she adds with a laugh, “you can give humans good direction and then they can develop their own pace, and their own system. And, they don’t have to be fenced in to prevent them from running away.”


Contact the reporter at jgreco@planphilly.com

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