“Cassowaries are large, flightless birds related to emus and (more distantly) to ostriches, rheas, and kiwis”, writes Olivia Judson in the September issue of National Geographic magazine. How large? People-size: Adult males stand well over five foot five and top 110 pounds. Females are even taller, and can weigh more than 160 pounds. Dangerous when roused, they’re shy and peaceable when left alone. But even birds this big and tough are prey to habitat loss. The dense New Guinea and Australia rain forests where they live have dwindled. Today cassowaries might number 1,500 to 2,000. And because they help shape those same forests – by moving seeds from one place to another – “if they vanish”, Judson writes, “the structure of the forest would gradually change” too. (Photo by Christian Ziegler/National Geographic)

“Aurora Hunters”. Photographers taking part in a photography tour on the Lofoten Islands in Norway, pull over on the side of the road to take a photo of their first ever Aurora Borealis after spotting it from their tour bus. Photo location: Rystad, Lofoten Islands, Norway. (Photo and caption by Mark Gee/National Geographic Photo Contest)

Two stags fight in a wildlife park in Aurach near Kitzbuehel, in the Austrian province of Tyrol. (Photo by Kerstin Joensson/Associated Press)

Devotees ride on the roof of a train as they return to the city after attending the final prayers on the first phase of Bishwa Ijtema in Dhaka January 11, 2015. Hundreds of thousands of pilgrims congregated in the Bangladeshi capital Dhaka as the first phase of this year's Bishwa Ijtema, one of the biggest Islamic gatherings in the world after the Haj in Saudi Arabia, came to an end. (Photo by Reuters/Stringer)

People play on a beach along the Arabian Sea on a hot summer day in Mumbai, India, April 29, 2016. (Photo by Danish Siddiqui/Reuters)

One of the worlds shortest models Mary Russell at 4 feet 1 inch with 6 foot model Georgia Meacham in London, UK on June 16, 2016. The 4ft1 beauty suffers with achondroplasia a medical term for dwarfism, which means she has as average sized torso but short arms and short legs, with an oversized head. As well as stifled growth, Mary also suffers with sciatica and spinal stenosis, an abnormal narrowing of the spinal canal – which cause agonising nerve problems, leaving her in excruciating pain and unable to stand for long periods of time. The condition leaves Mary, 47, struggling with everyday tasks things most people take for granted like going to the supermarket, getting cash from an ATM and ordering a drink at a bar become a challenge. (Photo by Simon Jacobs/Caters News Agency)

Volunteers try to keep alive some of the hundreds of stranded pilot whales after one of the country's largest recorded mass whale strandings, in Golden Bay, at the top of New Zealand's south island, February 10, 2017. Volunteers in New Zealand managed to refloat about 100 surviving pilot whales on Saturday, February 11, 2017 and are hoping they will swim back out to sea after more than 400 of the creatures swam aground at a remote beach. (Photo by Ross Wearing/Reuters)

People take pictures of 30 Rockefeller Plaza as it is lit in the colors of the Democratic and Republican parties ahead of the U.S presidential election in Manhattan, New York, U.S., November 7, 2016. (Photo by Andrew Kelly/Reuters)