Whales are long-lived, from 70-150 years, and slow to reproduce. It makes them very vulnerable to population collapses. Blue whales – the biggest animal to have ever existed - have still not recovered from being hunted to the brink of extinction. Only one population, the East Pacific grey whale, is thought to have recovered to its pre-hunting levels, but the closely related West Pacific grey whale population is the most endangered in the world. It hovers on the edge of extinction with just over one hundred remaining. The north Atlantic right whales are endangered.