David Attenborough looks at why mammals are the most successful creatures on the planet. Mammals have adapted to live almost ...

Whales, like most mammals, give birth to live babies . Whales give birth to one calf at a time. A whale calf stays in its mother's womb for between 10 and 16 months, depending on the species.

Thousands of blue whales roam the oceans and the giant mammals give birth every two to three years. But the births are very stealthy, with calves rarely sighted.

Whales, like most mammals, give birth to live babies . Whales give birth to one calf at a time. A whale calf stays in its mother's womb for between 10 and 16 months, depending on the species.