Nature's heavyweights

The great bustard is Europe's heaviest flying bird. It can weigh more than 15 kilograms (33 pounds). It lives in open spaces, which have become few and far between in many countries because of intensive farming. Its size helps ward off predators, but its weight also means it flies low and often collides with power lines.

Ostriches are the world's biggest birds, although they don't fly. With a height of up to 2.7 meters (9 feet) and weighing in at 156 kilograms, they make humans look tiny. That doesn't prevent people killing them for meat, though. Ostrich steaks have made their way onto menus around the world.

The European bison or wisent, the heaviest surviving land animal in Europe, was once hunted almost to extinction. Today, it thrives especially in Poland's famous, wild Bialowieza forest. Unfortunately, the forest is at the heart of a battle beween environmentalists and the Polish government over logging.

Bears are the world's largest living land carnivores. They can measure 3 meters tall when they stand on their hind legs. It's fun to watch them fishing — from a safe distance, of course.

Polar bears, officially classified as a marine mammals, are on average slightly larger than their brown-furred relatives. Their cute and cuddly appearance makes them extremely popular. But climate change is destroying Arctic sea ice, which is essential for the polar bear's survival.

The African elephant is the earth's largest living land animal. The biggest can be up to 7.5 meters long and 3.3 metres tall. They can weigh a hefty 6 metric tons (6.6 tons) at most. One of their unique features is very large ears, which allow them to radiate excess heat and stay cool.

Unsurprisingly, giraffes take the award for being the tallest animals in the world. Towering over us, they grow as tall as 5.5 meters. Even giraffe calves are born at 1.8 meters tall. A lesser known fact is that they are the animals with the highest blood pressure. They need it to pump blood through their long, long necks.

Saltwater crocodiles are the longest living reptiles.They can grow to up to 6 meters long. The biggest recorded is said to have weighed a staggering 1.9 metric tons. "Salties" are feared as "man-eaters," unlike their smaller freshwater crocodile relatives, which will only bite if threatened.

The whale shark is actually a fish, indeed the world's biggest. This one is nearly 6 meters long; they can grow to twice this length. Whale sharks used to be hunted as food, but eco-tourism has helped save the once-endangered fish. These days, whale sharks and humans swim happily side by side.

The majestic blue whale beats all the records as the planet's biggest animal. In fact, it is considered the biggest animal that has ever existed. They can weigh up to 180 tonnes and grow to up to 30 meters long. They were hunted almost to extinction in the 20th century, until they were protected in 1966.