Bottlenose dolphin  (Tursiops truncatus)

The bottlenose dolphin is one of the most well-known species of dolphin (2). There appear to be two main varieties; a smaller, inshore form and a larger, more robust form that lives mainly offshore (6). This stocky species has a torpedo-shaped body, a short beak and pointed flippers (2). They are usually dark grey on the back with paler grey flanks and a white or pinkish belly (7). The sickle-shaped dorsal fin is tall, and positioned centrally on the back; variations in the shape of the dorsal fin along with scars and other markings on the skin can help researchers to identify individuals (8).

Found in coastal waters of most temperate, tropical and subtropical areas (9). Around the UK, it occurs in the English Channel, around north-east Scotland and in the Irish Sea, particularly in Cardigan Bay and off south-east Ireland (5). It is also found off western Ireland (5), but is rare further north than the UK (6).

Coastal and oceanic, inhabiting a range of habitats from open water and lagoons to rocky reefs (10). It also occurs in large estuaries and even the lower reaches of rivers and harbours (6).

This active species engages in much energetic behaviour, including breaching (clearing the water), lobtailing (slapping the tail flukes down onto the surface of the water) and bow-riding (riding the swell created in front of boats and even large whales) (8). They have been observed 'playing games' with seaweed and other objects (8).

Dolphins are highly intelligent animals; they have a sophisticated echolocation system and communicate via a range of sounds (9). Although lone individuals occur, this is typically a very sociable animal, living in groups numbering between 10 and 100 individuals; even larger groups may form offshore (10). This species has a broad diet, a wide variety of fish and invertebrates including cephalopods are taken (2). They vary their hunting methods greatly, and cooperative hunting has been observed in many areas (2). In Brazil, this species even hunts cooperatively with humans, driving fish into the nets of local fishers. In return, the dolphins take their share of the fish (2).

Females produce a single calf in the summer after a gestation period of 12 months. The calf suckles for up to 18 months and stays close to the mother until it reaches four or five years of age (7).

The bottlenose dolphin faces a number of threats including human disturbance, entanglement in fishing nets, and hunting. Like all cetaceans they are vulnerable to chemical and noise pollution. The captivity industry that supplies the world aquarium trade is also a problem (8).

The bottlenose dolphin is a UK Biodiversity Action Plan (UK BAP) priority species (5). It is protected in UK waters by the Wildlife and Countryside Act 1981 and the Wildlife (Northern Ireland) Orders 1985; it is illegal to intentionally kill, injure, or harass any cetacean species in UK waters (5). The Agreement on the Conservation of Small Cetaceans in the Baltic and North Seas (ASCOBANS), has been signed by 7 European Countries, this includes the UK. Provision is made under this agreement to set up protected areas, promote research and monitoring, pollution control and increase public awareness (5). Under Annex II of the EC Habitats Directive, candidate marine Special Areas of Conservation (SACS) are being set up for this species in Cardigan Bay (Wales) and the Moray Firth (north-east Scotland) (5).

For more on the bottlenose dolphin see:

• The Mammal Society's fact sheet:
  www.abdn.ac.uk/mammal/dolphin.shtml
• The WDCS homepage:
  www.wdcs.org/
• MarineBio.org:
  http://marinebio.org/species.asp?id=33

Information authenticated by WDCS, The Whale and Dolphin Conservation Society.
http://www.wdcs.org