The World's Biggest Beasts: Here and Gone (Photos)

Here: Hippo

(Image credit: Credit: John De Boer / Stock.XCHNG)

Common hippos, Hippopotamus amphibious, are the second heaviest land mammals. I mean, just look at them! Pudgy!. A hippo can be as long as a small car. Hippo populations have shrunk dramatically, and experts fear some populations could go extinct by the end of this century.

Here: Elusive Squid

(Image credit: AP Photo/HO, National Science Museum)

Previously thought to be a mythical creature, giant squid are real. A team led by Tsunemi Kubodera, from the National Science Museum in Tokyo, tracked and photographed this 26-foot long squid as it attacked prey nearly 3,000 feet deep off the coast of Japan's Bonin islands. Though some have said giant squids (more photos) are as long as 60 feet, scientists recently determined they’re more like 40 feet (12 m) long.

Here: Manatee

(Image credit: Credit: AquaMarine Images Photo Gallery)

An adult manatee can be 13 feet long (4 meters) and weigh up to 1,300 pounds (590 kg). Does that sound like a mermaid to you? They've been confused for such, and they’re also known as the "cows of the sea." Manatees are closely related to elephants. Various species of manatee are considered endangered or vulnerable, though in early 2016 the U.S. Fish and Wildlife Services said they are making a comeback. And on that bright note, this list comes to an end.

Robert Roy Britt

Robert is an independent health and science journalist and writer based in Phoenix, Arizona. He is a former editor-in-chief of Live Science with over 20 years of experience as a reporter and editor. He has worked on websites such as and Tom's Guide, and is a contributor on Medium, covering how we age and how to optimize the mind and body through time. He has a journalism degree from Humboldt State University in California.