Invasive Nutria Nuke Native Vegetation and Watersheds

Watershed Press Release – Salem Keizer Watershed Councils
April 2, 2004
Bob Roth – Salem Keizer Watershed Coordinator
Expanding nutria colonies threaten watershed health and restoration efforts by overgrazing native vegetation and increasing stream bank erosion. Salem area watershed groups are responding to this threat while increasing their financial stability.

Nutria are semi-aquatic rodents native to several countries in South America and they were introduced into the United States by the fur breeders. They have large webbed hind feet and average 16 pounds in weight. Nutria preferred food includes roots and stems of aquatic vegetation but they will also graze on grass, riparian plants, and agricultural corps. In the United States nutria often produce two litters a year with 4-6 offspring in each litter. While hawks, owls and eagles hunt nutria, predators have minimal population impacts in urbanized areas.

Nutria are pervasive in Salem steams and ponds, often grazing on expensive native plants installed during restoration projects such as the Claggett Creek Mitigation Project in Keizer. Decreased vegetation cover increase sunlight exposure, resulting in higher water temperatures and degraded wildlife habitat. Nutria burrowing into pond and stream banks negatively impacts water quality by increasing soil erosion and sedimentation. They also undermine mature trees adjacent to Mill Creek causing then to fall prematurely. Nutria even threaten dirt berms and dykes that are key structures in many ponds and lakes.

The Claggett Creek Watershed Council facilitated implementation of the ¼ mile long mitigation project in Claggett Creek Park. Nutria began feasting on the vegetation soon after planting completion. Plastic net tubes offered limit protection especially in areas where water levels vary widely such as floodplains.

Watershed council staff secured a box of Plantskydd and treated several native plants in heavily grazed project sections along Claggett Creek. Site monitoring revealed that that local nutria avoided treated plants at the site. The Salem Keizer Watershed Councils Association umbrella organization decided to become a Plantskydd dealer to provide property owners with additional plant protection options and to raise money for watershed activities. Plantskydd is a dried and sterilized animal blood mix which is sprayed on vegetation after mixing with water. In addition to nutria and beaver, Plantskydd has been effective in repelling deer and elk.