There are 13 species of great whale and several species of smaller whales. Some of them, like the blue whale and fin whale, are found in seas all over the world - including around the UK. Others are unique to particular areas.
Whales can be divided into two types - 'toothed' and 'baleen' (filter-feeders):
Baleen (or whalebone) whales - including the blue and humpback whale - get their name from the comb-like baleen plates that hang from the roof of their mouths. Made of stiff, flexible material similar to human fingernails, baleen acts like a sieve, so the whale can strain plankton, krill and small fish out of the water.
Toothed whales - including the sperm whale, as well as smaller cetaceans like dolphins - hunt fish, squid and other marine mammals. They have well-developed echolocation to help them spot prey and other whales.
Despite decades of legal protection, seven of the 13 great whale species are endangered or vulnerable. There are thought to be fewer than 5,000 blue whales in the world.
Why whales need help
Around 30,000 small whales, dolphins and porpoises die each year because they get entangled in fishing gear and drown. Known as ‘bycatch,’ this accidental catch is one of the biggest threats to cetaceans.
Whaling is another huge problem. Systematic over-exploitation has brought some species of whale close to extinction. In the Antarctic alone, more than two million whales were killed by commercial whalers during the 20th century.
In 1986 the International Whaling Commission (IWC) banned commercial whaling. But loopholes in the rules mean whales can still be hunted for 'scientific purposes' - for example by Japan and Iceland.
Other threats facing whales include being struck by ships, chemical pollution from industry, disturbance by noise from navy operations and seismic surveys (for oil exploration etc), and depletion of prey as a result of overfishing.
What we're doing - and how you can help
Our work to reduce the threats to whales incudes campaigning for an end to ‘scientific whaling’ through the International Whaling Commission (IWC).
We've also campaigned successfully for the IWC to start tackling other conservation issues such as bycatch, but more action is still needed.
In 2012, we successfuly campaigned against an oil and gas development in far-eastern Russia, which threatened the critically endangered Western gray whale population. We're continuing to push for stronger conservation measures to protect these whales.
We also vigorously campaigned for the creation of the substantial international whale sanctuary surrounding Antarctica, which came into being in 1994 after a historic international agreement.
In 2005, we introduced our Cetacean Species Action Plan, the first global conservation plan for all cetaceans (whales, dolphins and porpoises). It addresses all the key threats to whales.
We've been working with the Yubarta Foundation in Colombia for more than 10 years to conserve the humpback whale. Around 5-7% of the world’s humpback population is found in this area. Its migration route is the longest of any whale species in the world, extending from southern Chile to central Colombia (8700 km).
We've increased marine and coastal protected areas in the region by at least 20%. This ensures that habitats are legally protected, well managed and adequately financed.
Sustainable fishing agreements and practices have been adopted by local fishermen in at least three key areas. This reduces the risk of food depletion and of whales being caught as bycatch.