Children ride on the animal theme merry-go-round at the Smithsonian National Zoological Park during the Zoolights holiday display, in Washington, DC., Sunday, December 15, 2013. (Andrew S Geraci/The Washington Times)
Hundreds of people tour the Smithsonian National Zoological Park to enjoy the Zoolights holiday display, in Washington, DC., Sunday, December 15, 2013. (Andrew S Geraci/The Washington Times)
Children ride on the animal theme merry-go-round at the Smithsonian National Zoological Park during the Zoolights holiday display, in Washington, DC., Sunday, December 15, 2013. (Andrew S Geraci/The Washington Times)
Hundreds of people tour the Smithsonian National Zoological Park to enjoy the Zoolights holiday display, in Washington, DC., Sunday, December 15, 2013. (Andrew S Geraci/The Washington Times)
Hundreds of people tour the Smithsonian National Zoological Park to enjoy the Zoolights holiday display, in Washington, DC., Sunday, December 15, 2013. (Andrew S Geraci/The Washington Times)
Children ride on the animal theme merry-go-round at the Smithsonian National Zoological Park during the Zoolights holiday display, in Washington, DC., Sunday, December 15, 2013. (Andrew S Geraci/The Washington Times)
Hundreds of people tour the Smithsonian National Zoological Park to enjoy the Zoolights holiday display, in Washington, DC., Sunday, December 15, 2013. (Andrew S Geraci/The Washington Times)
Christmas lights hang from a tree at the Smithsonian National Zoological Park as part of Zoolights holiday display, in Washington, DC., Sunday, December 15, 2013. (Andrew S Geraci/The Washington Times)
Hundreds of people enter the Smithsonian National Zoological Park to enjoy the Zoolights holiday display, in Washington, DC., Sunday, December 15, 2013. (Andrew S Geraci/The Washington Times)
Lights from cars buzz by the Zoolights sign outside of the Smithsonian National Zoological Park, in Washington, DC., Sunday, December 15, 2013. (Andrew S Geraci/The Washington Times)
Lights from cars buzz by the Zoolights sign outside of the Smithsonian National Zoological Park, in Washington, DC., Sunday, December 15, 2013. (Andrew S Geraci/The Washington Times)
The female giant panda cub at the Smithsonian's National Zoo is measured on Friday, Nov. 29, 2013, in Washington. (AP Photo/Smithsonian's National Zoo, Abby Wood)