“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)

Some foods have significantly more Calories than others but what does the difference actually look like. Each of the photographs below represents 200 Calories of the particular type of food; the images are sorted from low to high calorie density. When you consider that an entire plate of broccoli contains the same number of Calories as a small spoonful of peanut butter, you might think twice the next time you decide what to eat. According to the U.S. Department of Agriculture, the average adult needs to consume about 2000 – 2500 Calories to maintain their weight. In other words, you have a fixed amount of Calories to "spend" each day; based on the following pictures, which would you eat?

A freshwater stingray pup looks out from a holding tank at Bristol Zoo's aquarium on January 20, 2012 in Bristol, England. (Photo by Matt Cardy/Getty Images)

Dr. Lisa Ballance (NOAA Fisheries Service) with a curious calf – this is a Type C killer whale, a fish-eater.

Dafna Ben Nun with the Emperor penguins. Heres the brilliant picture of a cheeky baby penguin playfully winking at a photographer. The adorable snap was taken while a group of mischievous chicks were playing with their parents. (Photo by Dafna Ben Nun/Caters News)

Isabel Schmalenbach, an environmental scientist with the Helgoland Biological Institute (Biologische Anstalt Helgoland), part of the Alfred Wegener Institute for Polar and Marine Research, holds a one-year old baby European lobster (Homarus gammarus) raised at the institute on August 3, 2013 on Helgoland Island, Germany. Later in the day Schmalenbach and her colleagues released a total of 415 one-year old lobsters into the North Sea as part of an effort to repopulate the lobster population around Helgoland (also called Heligoland). In the 19th century local fishermen caught up to 80,000 lobsters a year in the surrounding waters, combined with the heavy allied bombing of the island during and after World War II, as well as other environmental factors, decimated the lobster population. (Photo by Sean Gallup)

Sultan, a famous captive fennec that is displayed tied on a rope in front of a tourist shop, is the main attraction in the souk of Douz, a desert town in Tunisia. By the display of such a charismatic animal, tourists are often lured to buy things or pay for pictures. On inquiry, although Sultan has been caught as a pup in the wild, the owners of the shop reassure the foreigners stating that the animal is ‘domestic’. (Photo by Bruno D’Amicis/Fritz Pölking Prize/GDT EWPY 2015)