Nat’l Wildlife Refuge Goes To The CowsThe Sherburne National Wildlife Refuge is a recreation destination. But this summer, some of the biggest animals there are cows. About an hour north of the Twin Cities, the refuge is more than 30,000 acres of oak savanna and wetlands. But some invasive plant species are threatening to change this habitat. So they're trying a new way to control the undesirable plants, letting cows eat them.