The Common Dolphin (Delphinus Delphis) is not so well-known off the Welsh coast as its larger though less numerous cousin, the bottlenose Dolphin (Tursiops Truncatus) which has a healthy and flourishing population in Cardigan Bay.
But this smaller member of the cetacean family, which of course includes whales and porpoises, has possibly had a more distinguished press, for it was the common colphin and not the cottlenose which was frequently represented in the art and literature of ancient Rome and Greece and also featured in the popular TV serial ‘Flipper’ so beloved of children a generation ago.
Common Dolphins come in two species, the long-beaked (Delphinus Capensis) and short-beaked (Delphinus Delphis), so there was some confusion with the bottlenose, even among cetologists until fairly recent times. It is the bottlenose that features in Marine Parks and Aquatic Shows, so the general misconception is understandable. The Common Dolphin is between 6.2 and 8.2-feet long and weighs between 180 and 518-lbs as opposed to the bottlenose at between 10 and 14 -feet long and weighing up to 1,100-lbs. It is sometimes confused with the porpoise, although the porpoise never leaps out of the water. The back is black or dark grey and the belly white with a long double-arched ‘hourglass’ pattern on the side, the front half often tinged cream or gold and the back part a rather dirty-looking grey. Common dolphins are frequently seen in the Irish Sea and around the Irish coast and they seem to love bow-riding ahead of boats, often in large numbers. Passengers on ferries and cruise ships often see them around their boat for long periods, riding the bow waves with great enthusiasm. This is particularly the case in the Irish Sea, the Western approaches and the Bay of Biscay. They can often live in gatherings of hundreds and, in some parts of the world, in thousands where conditions are favourable. They sometimes dive to a depth of over 600 feet in their favourite habitat along shelf edges and in areas where there is sharp seabed relief, and are seldom seen near the shore. They swim swiftly and in close formation and delight in aerobatics well clear of the surface. They are not common in aquatic shows, but on several occasions rescued common dolphins have integrated with bottlenose dolphins in Seaworld, San Diego and at Discovery Cove. One, indeed, managed to mate with a female bottlenose at Seaworld, producing four hybrid ‘bolphins.’
The common dolphin is extremely vulnerable to fishing nets and other man-made devices and this has led to the development of ‘dolphin-friendly’ gear and techniques, which has been widely welcomed by conservationists. But they are still hunted and accidentally caught by fishermen in some other parts of the world. Nevertheless, the short-beaked common dolphin is the most numerous and widest spread cetacean in the world. The population in the Celtic Deep area in 1994 was estimated at around 75,000 animals.