Marine mammals include some of the most fascinating animals on Earth. Large, majestic whales and stunning, playful dolphins have provided mysterious companionship to humans at sea for hundreds of years. These magical creatures, along with the equally fascinating manatees, dugongs, seals, sea lions, and walrusses, have developed a completely different set of adaptations from their terrestrial ancestors and relatives. Volume 4 of the HMW series provides complete accounts of all species and families in these important groups. Lavishly illustrated with colour photographs showing different behaviours of all of them, the text contains the latest up-to-date information on all families of sea mammals.