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Ann Wessel , Published August 04 2013

At Minnesota wildlife refuge, cows help with upkeep

ZIMMERMAN, Minn. – Hybridized cattails homogenize waterfowl habitat. Invading shrubs overtake once-open oak savannas. Non-native grasses choke out nutrient-rich plants.

Enter the Herefords.

Big appetites and sharp hooves of the 250-head herd that started grazing segments of 1,300 fenced-off acres within Sherburne National Wildlife Refuge in mid-May are making fast work of what would otherwise require considerable manpower and money – not to mention fire, fuel, chemicals and mowers.

Grazing is new to the refuge but not to Steve Karel. The refuge manager who joined Sherburne in August, Karel ran similar U.S. Fish & Wildlife Service grazing programs in Kansas and Nebraska. He describes it as one more tool in the management arsenal.

And the arrangement costs taxpayers nothing.

“They gain weight on cows and we’re getting habitat management done,” Karel said.

The project required 6 miles of fencing, at a cost of $10,000 a mile. A Legacy Amendment grant paid for 4 miles; revenue from the grazier offset staff costs to fence 2 miles.

The grazier pays about $11 per animal unit per month after deductions. A cow-calf pair is 1.2 animal units. Graziers receive deductions for efforts such as fencing, hauling water and rotating the cattle frequently.

On a recent tour, Karel and wildlife biologist Tony Hewitt showed early effects of grazing on the site chosen in part because it contains elements of three habitats targeted for preservation – wetlands, oak savanna and upland prairie.

Despite a delay brought on by a lingering winter followed by a wet spring that found cattle belly-deep in water – and therefore confined to the edges of cattail-choked pools – progress was evident two months in to a grazing season that will run through August.

By mid-July, cattails on the periphery were a foot or two shorter than those in the center. The animals cut into the duff layer, which can extend 12 inches deep and keeps other plants from taking hold.

The U.S. Fish & Wildlife Service refers to a 1985 study that estimated the globally imperiled oak savanna covered only .02 percent of its historic range in the Midwest.

Because the refuge lies within the transition zone between prairie and hardwood forest, the battle to curb shrubs never ends.

In the upland prairie areas, where Karel is happy to see plants such as big bluestem making a comeback, cattle crush some of the shrubby plants they do not eat.

The cattle will help to control cool-season grasses such as bromegrass and Kentucky bluegrass. Grazing will allow warm-season grasses such as big and little bluestem, Indian grass, sideoats grama and switchgrass to take hold.

Hoof action also helps to control invasive species such as reed canary grass that spread by rhizomes.

“Really, it’s not a battle of what we see above ground. It’s a battle of what’s below ground,” Hewitt said.

Even with a management plan accelerated by grazing, Karel said the work he and his staff accomplish will be just one part of a bigger picture.

“We’re here to put a piece or two in the puzzle. It’s way beyond me being here,” he said. “These habitat improvements, these are all things that are going to take time. But if we don’t do something, we’re going to lose it.”