Two female revelers engage in a beer drinking contest in the Hacker Pschorr tent on the first day of the 2017 Oktoberfest beer fest on September 16, 2017 in Munich, Germany. Oktoberfest is the world's largest beer celebration and typically draws over six million visitors over its three-week run. Oktoberfest includes massive beer tents, each run by a different Bavarian brewer, as well as amusement rides and activities. (Photo by Philipp Guelland/Getty Images)

A Palestinian boy takes part in a military-style summer camp being held by the Islamic Jihad movement during the youngsters' summer school vacation in Khan Younes town, in the southern Gaza Strip, 13 July 2016. Thousands of youngsters between the age of six and 16 can participate in the summer camp where they receive military as well as religious training. (Photo by Hatem Omar/EPA)

Soldiers from 12 Mechanized Brigade perform a simulated casualty evacuation at the Ministry of Defence training area at Copehill Down on Salisbury Plain on March 9, 2012 in Wiltshire, England. The Defence Secretary Philip Hammond visited the military facility to meet soldiers from the Brigade who are shortly to deploy to Afghanistan for Operation Herrick 16, and troops from the 3rd Battalion, the Yorkshire regiment which lost five of the six men who died this week in the deadliest single attack in Afghanistan since 2001. (Photo by Matt Cardy/Getty Images)

A young boy plugs his ears as his sister (C) and nanny (L) watch from Gravelly Point Park as planes land at Reagan National Airport in Arlington, Virginia on June 29, 2017. President Donald Trump' s travel ban on people from six mostly Muslim countries will come into force late Thursday, as controversy swirls over who qualifies for an exemption based on family ties. (Photo by Jim Watson/AFP Photo)

Odin, a five year-old White Bengal Tiger dives for a piece of meat thrown to him by a trainer during a big cat show at Six Flags Discovery Kingdom June 1, 2007 in Vallejo, California. Unlike most cats that are afraid of water, Odin loves diving in the pool to retrieve bits of meat fed to him by his trainers. (Photo by Justin Sullivan/Getty Images)

An orphaned 11 month old cougar cub plays at Six Flags Discovery Kingdom on April 26, 2007 in Vallejo, California. Three cougar cubs were given to the park from the Idaho Fish & Game in March after they were found motherless in the wild and it was determined that they would not survive in the wild. (Photo by David Paul Morris/Getty Images)

Taronga Zoo's elephant baby, as yet unnamed, is seen at Taronga Zoo on March 12, 2010 in Sydney, Australia. The Asian Elephant calf has continued to make progress following a protracted labour that spanned six days. The calf was originally believed to have died in the womb during labour but surprised veterinarians and zoo staff with an unexpected delivery early Wednesday morning. (Photo by Bobby-Jo Vial/Taronga Zoo via Getty Images)