Supporters of the presidential candidate Muhammadu Buhari and his All Progressive Congress hits with a motorbike another supporter during celebrations in Kano March 31, 2015. Nigeria's opposition APC declared an election victory on Tuesday for former military ruler Buhari and said Africa's most populous nation was witnessing history with its first democratic transfer of power. (Photo by Goran Tomasevic/Reuters)

A general view shows solar panels to produce renewable energy at the photovoltaic park in Les Mees, in the department of Alpes-de-Haute-Provence, southern France March 31, 2015. The solar farm of the Colle des Mees, the biggest in France, consists of 112,780 solar modules covering an area of 200 hectares of land and representing 100 MW of power. (Photo by Jean-Paul Pelissier/Reuters)

In this Wednesday, March, 5, 2014 photo, Afghan female boxers practice at the Kabul Stadium boxing club, Afghanistan. The women, who are 18 and older, don't have much more than determination, and a trainer who runs them through their paces, watches as they spar, corrects their technique, tells them when to jab, how to protect themselves, when to power through with a left and then a right. (Photo by Massoud Hossaini/AP Photo)

Andy Goldfarb, a staff biologist at the Point Defiance Zoo & Aquarium, plays with one of the four clouded leopard cubs currently at the zoo Friday, June 5, 2015 in Tacoma, Wash. The quadruplets were born on May 12, 2015 and now weigh about 1.7 lbs. each. Friday was their first official day on display for public viewing, usually during their every-four-hours bottle-feeding sessions, which were started after the cubs' mother did not show enough interest in continuing to nurse them. (AP Photo/Ted S. Warren)

Engineer Thomas Dwyer stands with the new Bionic Exoskeleton next to Amanda Boxtel during its launch at the Excel centre on October 21, 2011 in London, England. The bionic device developed by Ekso Bionics is a wearable, battery-powered, robotic exoskeleton, designed to aid wheelchair users and those who have suffered from spinal chord injuries to stand and walk. (Photo by Dan Kitwood/Getty Images)

Crowd reaction outside the court for the Dr. Conrad Murray trial verdict on November 7, 2011 in Los Angeles, California. Murray was convicted in the 2009 death of pop singer Michael Jackson from an overdose of the powerful anesthetic propofol. Sentencing will take place November 29. (Photo by Toby Canham/Getty Images)

From stuffed elephants to picnics under power lines, Leipzig-born photographer Frank Herfort coaxes magical, colour-saturated tableaux from intriguing slices of everyday Russian life. Here: A lonely dog watches the mailboxes in a typical Moscow residential block. (Photo by by Frank Herfort/The Guardian)

These powerful images capture the spear-wielding tribes of Papua new Guinea who believe they are possessed with the spirit of the crocodile. They show how the Kangunaman clansmen scar their backs to resemble reptile scales while the Huli Wigmen wear elaborate headdresses to signal they are ready for battle. (Photo by Trevor Cole/Media Drum World)