MEDORA, N.D. (AP) — The National Park Service is periodically closing some backcountry trails in Theodore Roosevelt National Park as officials continue work to thin the elk herd there.

Superintendent Valerie Naylor says the trails in the park's South Unit will be closed on Tuesdays, Wednesdays and Thursdays during the project. Roads, overlooks and the Cottonwood Campground are not affected.

The park in the western North Dakota Badlands is in the maintenance phase of an elk management plan that included large reduction efforts in 2010 and 2011 in which nearly 900 elk were killed. The herd had grown to more than 1,200 animals, when the ideal size for the park is between 100 and 400.

Only 69 elk were killed last year, and only about 40 are being killed this year.

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