World Whale Day falls on the third Sunday of February, which is February 15th this year. It reminds us of the challenges faced in our oceans. Some of the most fascinating creatures live in our big blue oceans. Whether the mammoth blue whale or the enchanting narwhal, whales are mysterious animals. For centuries they've been hunted for their meat and oil, and today they also face pollution and loss of habitat. World Whale Day raises awareness of the growing need to protect these diverse and majestic mammals. 

What do you know about these giants in the ocean? 

In terms of taxonomy, their closest living relatives are the hippos. In fact, whales and hippos origin from the same ancestor about 40 million years ago. 

In Chinese, orcas are called "tiger whales" or "killer whales." However, orcas are not whales, they are large dolphins. 

Everyone knows that blue whale is the largest known creature in the world. A blue whale can grow up to 30 meters and weigh 190 tons. Only its heart can weigh 200 kilograms. And the walls of the arteries in the heart have been described as being "as thick as an iPhone 6 Plus is long."

The dwarf sperm whale, the smallest whale, only measures 2.6 meters and weights 135 kilograms, about the size of a tiger. 

There are about 42 different species of whales, divided into two groups: baleen whales and toothed whales. The 15 species of baleen whales include right whale, blue whale, humpback whale, grey whale and others. They have baleen plates instead of teeth, and feed on plankton. Toothed whales consist of mainly sperm whales and beaked whales. They are predators and can hunt with sharp teeth, but they can't chew. 

The right whale has one of the largest heads in the animal kingdom, taking up to 40 percent of its whole body. Most of this big head is a big mouth: as one of baleen whales, right whale needs a super large mouth and many baleen plates to filter plankton from the seawater. But the right whale does not have the largest brain among the whales, this honor goes to the sperm whale: it has the largest brain known of any modern or extinct animal, weighing on average 7.8 kilograms, five times heavier than a human's. 

Sperm whale may be the diving champion of mammals. It can dive 1-2 kilometers deep, stay underwater for up to 90 minutes without going to the surface to breathe. This "superpower" is necessary for sperm whales, as they spend most of their time diving in the deep ocean and hunting squids. 

Whales do not have outer ears. Instead, they receive sound through their throats, from which it passes to the inner ear. This can help them hear better in the water. 

Because it is as thick as toothpaste. This milk contains high amounts of fat, which is meant to help the calf develop more blubber and as quickly as possible. 

Some whales, such as belugas, are kept in captivity and trained to do tricks in animal performances. Please do NOT support those shows, as whales breeding programs have been unsuccessful so far; most whales in performance are caught from the wild and separated from their families. Many of them die within months, even weeks after being captured. 

(Cover Photo via VCG)

(If you want to contribute and have specific expertise, please contact us at nature@cgtn.com.)