These two young siblings appear to cling on to a tree for dear life and even hold hands as they learn the ropes of climbing, on June 25, 2013. (Photo by Tim Fitzharris/Minden/Solent)

Female sea lion “Sarasa” holds a hose with her mouse to help a trainer clean her room at the Shinagawa Aqua Stadium aquarium in Tokyo on December 30, 2014. The aquarium is carrying out year-end general cleaning of their facilities. (Photo by Yoshikazu Tsuno/AFP Photo)

People look at a loaded truck that got stuck in a sinkhole on a road in Guilin, Guangxi Zhuang Autonomous Region, January 7, 2015. No injury was reported, according to local media. (Photo by Reuters/Stringer)

A Pakistani monkey handler Naseer Khan plays flute to attract passers by for a monkey show to earn his living in Islamabad, Pakistan, Monday, September 7, 2015. (Photo by B. K. Bangash/AP Photo)

Fish weighing over 80 kilogram is cooked in a hotpot during a food festival in Zhengzhou, Henan province, China, October 17, 2015. (Photo by Reuters/Stringer)

Heidi Klum attends the Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City. (Photo by Mike Coppola/Getty Images for Heidi Klum)

Members of ASC Tornados, the motorcycle display team of the Indian army, lie in a row on the ground as another performs a stunt by jumping over them during the 225th anniversary celebrations of Army Service Corps in Bangalore, India, Tuesday, December 8, 2015. The Army Service Corps which was established in 1790 is an arm of the Indian Army which handles its logistic support function. (Photo by Aijaz Rahi/AP Photo)

A handout photograph provided by Brian Kubicki of Costa Rican Amphibian Research Center on 26 April 2016 shows a “Crystal frog”, Hyalinobatrachium dianae (H. diane). This frog was discovered by US biologist Brian Kubicki and Costa Ricans Stanley Salazar and Robert Puschendorf in a rainy forest of Costa Rican caribbean after 40 years without notice of any new example of this kind. (Photo by Brian Kubicki/EPA/Costa Rican Amphibian Research Center)