Humpback whale 'lobtailing' in Chatham Strait. The whale brings its tail down hard on the surface of the water - a sound that can be heard for a distance of several hundred metres underwater. Taken by kayaking photographer Duncan Murrell
The family Delphinidae is the largest in the Cetacean order, and evolved relatively recently, about ten million years ago. There are almost forty species of dolphin in 17 genera all varying in size and shape.
The killer whale or orca (Orcinus orca) is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. Killer whales are found in all oceans, from Arctic and Antarctic regions to tropical seas.