Karis, an 8 week old lion cub, growls at a pumpkin as she explores a Halloween treat put in her enclosure by staff at Blair Drummond Safari Park near Stirling, Scotland, Tuesday, October 29, 2013. (Photo by Andrew Milligan/AP Photo/PA Wire)

A murmuration of starlings above the the small village of Rigg, near Gretna, in the Scottish Borders, on November 25, 2013. The weight of the resting birds on power lines caused some power localised power outages in the village. Still one of the commonest of garden birds, its decline elsewhere puts it on the Red List of endangered species. (Photo by Owen Humphreys/PA Wire)

Wedges of an orange generate enough current and electrical juice – 3.5 volts – to power an LED. The fruit’s citric acid helps electrons flow from galvanized nails to copper wire in this 14-hour exposure. This image was published in September’s Visions of Earth, a trio of photos that appear in each issue of National Geographic. (Photo by Caleb Charland/National Geographic)

HMS Dragonís Mk8 Lynx Helicopter conducted day into night flying serial by L(Phot) Dave Jenkins which won the Media Operations Category which was awarded to the best single image that is judged to create the most impact as a news in the annual Peregrine Trophy awards. (Photo by Dave Jenkins/PA Wire)

The UK VELUX Lovers of Light competition attracted 15,000 entries from amateur, professional and mobile phone photographers. Entrants were asked to create a landscape image which celebrates and captures daylight. The judges have whittled these down to a shortlist of ten finalists. The winner will be announced at the end of march with the snapper of the best shot winning a trip to Norway – which will be made during the summer period when the country experiences 24 hour daylight. Photo: “Carousel in the mist”; Prokoshko, Bosnia. (Photo by Marko Stamatovic/PA Wire)

Voters line up to cast their ballots at a polling station in the city of Qom, Iran. Elections for Iran's parliament (Majlis) and Assembly of Experts kicked off on Friday, February 26, 2016. (Photo by Ahmad Halabisaz/Xinhua via ZUMA Wire)

Competitor Isaiah Webb attends the 2017 Remington Beard Boss World Beard & Moustache Championships held at the Long Center for the Performing Arts on September 3, 2017 in Austin, Texas. (Photo by Brian Cahn/ZUMA Wire/Rex Features/Shutterstock)

An eight-year-old St Bernard with the longest canine tongue in the world, measuring 18.58cm (7.31in) in length, as recorded by the Guinness World Records: Amazing Animals, in South Dakota, USA. (Photo by Kevin Scott Ramos/GWR/PA Wire)