United States Park Rangers Josh Clemons, left, and Peter Zahrt close a trail at Mammoth Cave National Park, Ky. Tuesday, Oct., 1, 2013. National Parks across the country are closed due to the federal government shutdown. (AP Photo/The Daily News, Alex Slitz)

Photo by: Alex Slitz

United States Park Rangers Josh Clemons, left, and Peter Zahrt close a trail at Mammoth Cave National Park, Ky. Tuesday, Oct., 1, 2013. National Parks across the country are closed due to the federal government shutdown. (AP Photo/The Daily News, Alex Slitz)