Is that a caiman? Nope, it's a cat! And not just any cat  a black jaguar. World Wildlife Fund (WWF) CEO Carter Roberts recalls how a member of the WWF team spotted a dark shape moving through the water as the group was heading down the Tapajós River in Brazil's Juruena National Park. 

That shape turned out to be a large male black jaguar. Not a separate species, black jaguars are actually a rare colour variant and owe their dark pigmentation (and yellow irises) to a condition known as melanism. The coat might appear completely black, but spots are often visible if you look closely (which we wouldn't advise). Thanks to hunting and habitat loss, jaguars in general are pretty endangered cats, but black jaguars are an especially rare sight, with only around 600 of them thought to exist in the wild. The sighting of such a rare animal is proof of the region's ecological importance, Roberts says. Aside from jaguars, the Juruena National Park is a haven for other threatened species, including giant otters and harpy eagles.

Top header image: Joachim S. Müller, Flickr