This July 2014 image provided by the Bureau of Land Management shows the interior of the Natural Trap Cave in north-central Wyoming. The cave holds the remains of tens of thousands of animals, including many now-extinct species, from the late Pleistocene period tens of thousands of years ago. Scientists have resumed digging for the first time in more than 30 years. (Photo by AP Photo/Bureau of Land Management)

A visitor takes a photograph from the North Star observation capsule onboard the cruise ship Quantum of the Seas which is currently docked at Southampton on October 31, 2014 in Southampton, England. Billed as the world's first smartship, Royal Caribbean's Quantum of the Seas is claimed to be the most high-tech cruise ship in the world, with high tech modifications such as virtual balconies in windowless rooms and features such as the first dodgem ride on water, and a skydiving simulator. The ship will shortly begin its voyage from Southampton, where it docked earlier this week, to New York before relocating to the Caribbean for the 2014-15 season. (Photo by Matt Cardy/Getty Images)

Iraqi Kurdish refugees wait with children in Cukurca refugee camp in Turkey April 8, 1991. Reuters photographers have chronicled Kurdish refugee crises over the years. In 1991 Srdjan Zivulovic documented refugees in Cukurca who had escaped a military operation by Saddam Hussein's government in Iraq aimed at “Arabising” Kurdish areas in the north. Hundreds of thousands fled into Turkey and Iran. Images shot in recent months show familiar scenes as crowds of people flee Islamic State militants in Syria. There are as many as 30 million Kurds, spread through Turkey, Iraq, Syria and Iran. Most Kurds are Sunni Muslims, but tend to feel more loyalty to their Kurdishness, rather than their religion. (Photo by Srdjan Zivulovic/Reuters)

A long-tailed macaque grabs a necklace from a statue during the annual Monkey Buffet Festival at the Pra Prang Sam Yot temple in Lopburi, north of Bangkok November 30, 2014. The festival provides food and drinks to the local monkey population, which numbers more than 2,000, to thank them for drawing tourists to the town. (Photo by Damir Sagolj/Reuters)

Indonesian mahouts clean their Sumatran elephant in a river near the zoo in Medan, North Sumatra, Indonesia, 12 December 2014. According media reports, the smallest of the Asian elephants, Sumatran elephant (Elephas maximus sumatrensis) is facing serious pressures arising from illegal logging and associated habitat loss and fragmentation in Indonesia. The population has come under increasing threat from rapid forest conversion to plantations. (Photo by Dedi Sahputra/EPA)

Carlos Bahia, dressed as Santa Claus, talks with boys at the Maresias beach, in the state of Sao Paulo December 9, 2014. In the Southern Hemisphere summer starts on December 1, so while countries in the north are experiencing a white Christmas with grey skies, those in the south are busy surfing and sunbathing in temperatures just shy of 100 degrees Fahrenheit (38 degrees Celsius). (Photo by Nacho Doce/Reuters)

Women porters load bundles onto their back for transport across the El Tarajal boarder separating Morocco and Spain's North African enclave of Ceuta, in Ceuta on December 4, 2014. Unemployment among Ceuta and Melilla's native workforce is more than 30 percent – among the highest rates in Spain. Meanwhile, authorities say some 30,000 Moroccan traders and menial workers cross into each territory every day. (Photo by Jorge Guerrero/AFP Photo)

Brandy Shelton of Greensboro, North Carolina, “twerks” for a group of bikers on Ocean Boulevard during the 2015 Atlantic Beach Memorial Day BikeFest in Myrtle Beach, South Carolina May 22, 2015. After three people were killed and seven wounded in shootings during 2014 Bikefest, State officials called for an end to the event that draws thousands to the family-friendly beach town.Their efforts were unsuccessful. Bikers returned to Myrtle Beach – just a week after a bloody motorcycle gang shootout in Waco, Texas. But this time authorities are more prepared, with dozens of new surveillance cameras and a police force three times the size of last year's. (Photo by Randall Hill/Reuters)