Dolphins
Bottlenose Dolphin (Latin Name: Tursiops truncatus)
Bottlenose dolphins are grey, varying from dark grey at the top near the dorsal fin to very light grey and almost white or maybe even a pinkish colour at the underside. This makes them harder to see both from above and below when swimming. The elongated upper and lower jaws form what is called the rostrum and give the animals their name of bottlenose. The real nose however is the blowhole on top of the head, and the nasal septum is visible when the blowhole is open. Their face shows a characteristic "smile". The "smile" does not mean that they are happy. They are unable to move their jaw in any other position.
They swim at a speed of 5-11 kilometres per hour (3-6 mph); for short times, they can reach peak speeds of 35 kilometres per hour (21 mph). Every 5-8 minutes, the dolphins have to rise to the surface to breathe through their blowhole. Their sleep is very light; some scientists have suggested that the two halves of their brains take turns in sleeping and waking. It has also been suggested that they have tiny periods of 'microsleep'.
These dolphins normally live in groups called pods containing up to 12 animals. These are long-term social units. Typically, a group of adult females and their young live together in a pod, and juveniles in a mixed pod. Several of these pods can join together to form larger groups of one hundred dolphins or more. Males live mostly alone or in groups of 2-3 and join the pods for short periods of time.
The species is commonly known for its friendly character and curiosity towards humans immersed in or near water. It is not uncommon for a diver to be investigated by a group of them. Occasionally, dolphins have rescued injured divers by raising them to the surface, a behaviour they also show towards injured members of their own species. Such accounts have earned them the nickname of "Man's best friend of the sea".
Their diet consists mainly of small fish, occasionally also squid, crabs, shrimp, and other smaller animals. Their cone-like teeth serve to grasp but not to chew food. When a shoal of fish has been found, the animals work as a team to keep the fish close together and maximize the harvest. They also search for fish alone, often bottom dwelling species. Sometimes they will employ "fish whacking" whereby a fish is stunned (and sometimes thrown out of the water) with the tail to make catching and eating the fish easier.
Harbour porpoise (Latin name: Phocoena phocoena)
The harbour porpoise is one of six species of porpoise. As its name implies, it stays close to coastal areas or river estuaries and as such is the most familiar porpoise to whale watchers. This porpoise often ventures up rivers and has been seen hundreds of miles from the sea. It is sometimes known as the common porpoise in the UK.
The harbour porpoise is a little smaller than the other porpoises. It is about 75cm long at birth. Males grow up to 1.6m and females to 1.7m. The females are correspondingly heavier, with a maximum weight of around 76kg compared with the males' 61kg. The body is robust and the animal is at its maximum girth just in front of its triangular dorsal fin. The beak is poorly demarcated. The flippers, dorsal fin, tail fin and back are a dark grey. The sides are a slightly speckled lighter grey. The underside is much whiter, though there are usually grey stripes running along the throat from the underside of the mouth to the flippers. They live up to 25 years.
