Outer Banks wild horses thwart spread of destructive invasive plant — by eating it

An invasive plant known to grow in thick mats over water has met its match on North Carolina’s Outer Banks.

Wild horses on the barrier islands have developed a sweet tooth for watermilfoil, including an odd procedure for eating it that involves standing belly-deep in water for hours at a time.

The Corolla Wild Horse Fund shared video on Facebook of one such scene, showing an adult horse plucking mouthfuls of watermilfoil out of a canal in Carova Beach.

“Milfoil is a favorite among the Banker horses,” Corolla herd manager Meg Puckett told McClatchy News. “It does not have a lot of calories so the horses have to eat a lot of it for it to be actually nutritious.”

“Not many other animals will eat it. It grows in the canals (which are man-made), but also in the marsh and along the sound side,” she continued. “Wildlife folks spend a lot of time trying to keep it under control, because it can choke out an ecosystem so quickly.”

Historians believe the mustangs that roam the Outer Banks were left behind 500 years ago by colonists, and have adapted in countless ways to survive on the barrier islands.

This includes specialized ways of finding food and water. Their diet consists of “sea oats, coarse grasses, acorns, persimmons, and other native vegetation,” Visitcurrituck.com reports. The horses have also learned how to swim from island to island, when food and water becomes scarce.

Eurasian watermilfoil made its way to the U.S. as an ornamental aquarium plant. It was introduced in the 1940s and “is now considered one of the worst aquatic weeds, occurring in nearly every state,” according to the N.C. Department of Environmental Quality.

“It forms a dense canopy along the surface and shades out the vegetation below,” the state reports. “Water quality is degraded by the senescence of watermilfoil. Recreational activities are hindered. Water intakes get obstructed, and decaying mats can foul lakeside beaches.”

Puckett notes the plant is also a breeding ground for mosquitoes, which are a major pest on the Outer Banks.