There are three main species of Dolphin that live in and around the Bay of Gibraltar, the Common, Bottle Nosed and Striped.
The Common Dolphin is between 2.1m and 2.5m long, weighs 80Kg and swims at more than 70km per hour. It has a prominent, beaky nose with a dark grey to brown back. The dorsal fin is recurved and halfway along its back, the lateral fins are of medium size. The underside is pale grey to light yellow, and sometimes with tinges of pink. It looks as though it has a saddle on its back, hence the American name "Saddle Back Dolphin". This dolphin feeds on about 5Kg of sprats, sardines & herrings daily. There are around 200 in the bay.

The Striped Dolphin is very similar to the Common Dolphin but slightly slender. It is 1.8m to 2.5m long, weighs 68Kg and can swim through the water at more than 50km per hour. The top half is uniformly dark and is divided from the lighter bottom half by a prominent dark line running from eye to vent. Very common in the Bay of Gibraltar where they feed on sardines and shrimp.

The Bottle Nosed Dolphin is the biggest, measuring 2.7m to 3.7m long and weighing in at 181Kg. They can swim at a top speed of 50km per hour and have a prominent beak and dorsal fin which is recurved. They will eat most forms of fish life in quantities of up to 11Kg a day.

They are capable of diving to a depth of 280m and can stay below without breathing for 8 minutes. Some species can swim at speeds of 50-70kms per hour. In the wild they live arond 25 years, however, when taken at birth and put in captivity their life span is redced to 5 or 6 years.

Dolphins are social animals, spending all of their lives together in groups of varying numbers ranging from a family of three to hundreds. They work together using systems of organisation and cooperation, able to collaborate in order to obtain food and assist at giving birth. They have an awareness of social obligation towards each other whereas an injured animal will be supported on the surface by others to enable it to breathe. This awareness also extends to them aiding human beings in distress when in the water. They have also been known to help men to catch fish.

The bay is a favourite place for nursery schools of Dolphins, it is a very common sight to see baby dolphins accompanied by their mothers, rising to the surface a few inches away from each other when coming up to breathe. These mammals reproduce well in the warm waters of the Bay which are teeming with food.

They hunt collectively by corralling large shoals of fish into a compact group and taking turns to swim through the fish at high speed, catching several before coming out on the other side. Flying fish are one of the favourite food of the dolphins.

Dolphins find their bearings using sonar, they emit a series of high pitched clicks or squeaks and then wait for the echo to return. The direction and time taken for this return supplies them with the information as to the bearing and distance, and as they can vary the frequency and power of the sound beam, they can receive further information as to the size, shape and density of an object being scanned. They normally emit two types of sound, one linking the echo location and position of their food and the other for communication between individuals.

Their intellectual capacity is very high, superior to any other order, family or species, except human.
One of the manifestations of their intelligence, apart from their social structure, is that dolphins can adapt to constantly changing situations. Their intelligence seems to be directed along paths of enjoyment, which in themselves do not bring a physical reward but are rewarding mentally and in some cases appear to involve a sense of humour. In the Bay of Gibraltar there has been spotted a group of 50 dolphins taking it in turns to race around a circular path of about half a mile in diameter, this went on for an hour with much boisterous leaping and splashing and had nothing to do with feeding or mating, appearing to be some sort of contest. All this shows that these creatures require a large degree of mental stimulation.