Many people are unaware of the fact that dolphins are found in Irish inshore waters as wild animals as distinct from those found in marinas and aquaria. In the summer and autumn dolphins of a number of different species may be found off the south and west coasts in particular. They are feeding schools which follow the shoals of fish, crustacea and other marine animals brought inshore by the Gulf stream. Their presence is usually detected by the synchronised roll of their shiny backs as they break the surface of the sea to expel and inhale air. Occasionally they breach the surface spontane ously when they are accompanying a ship in a series of playful leaps. On these occasions their distinctive 'beaks' and swept back dorsal fins distinguish them from porpoises. They do not breed in Irish waters, preferring to rear their young elsewhere.

The Common dolphin (Delphinus delphis) is the species most likely to be encountered, being found regularly off the south and west coasts in schools of up to a hundred or more. It is generally steel-grey on the upper body and white under neath. There are large, oblong, ochre-coloured patches on either side of the body and wavy blackish lines along the sides extend up to the face. Usually about 6ft 6in. (2m) in length, it weighs up to 165lb. (75kg).

The other dolphin likely to be encountered in Irish waters is the Bottle-nosed Dolphin (Tursiops truncatus). Like the Common dolphin it occurs in schools but in numbers rarely more than a dozen. It is generally less abundant and apparently less widespread than the former. It is much larger than the Common dolphin, up to 11ft 6in. (3.5m) and is generally greyish-brown with white throat and belly. The name 'bottle-nosed' is derived from the strange snout or beak which is longer and more pronounced than that of the more common animal.

The Bottle-nose is the species most commonly tamed in aquaria, where it is taught to perform incredible tricks and to demonstrate its startling intelligence.

Other dolphins occur irregularly in Irish waters. On occasions two or more may be seen together or in the company of Porpoises.

Porpoise
Phocoena phocoen
Muc mhara

This is the commonest cetacean to be found in Irish waters. It occurs mainly in late summer and autumn but it may be encountered at any time of the year. It is commonest in schools of a few individuals together but it has been seen in dozens and occasionally in hundreds. Like the others of their kind, Porpoises pursue migrating shoals of fish, crustaceans and cuttlefish found in the Gulf stream along Ireland's southern and western seaboard. They are less frequent in the Irish sea and along the northern coasts. Porpoises are often accom panied by seabirds like gannets, shearwaters and petrels.

The Porpoise is smaller and stockier than the dolphins averaging about 5ft (1.5m) and 1101b. (50kg) in weight. It does not have the 'beak' so characteristic of the latter group instead the dome-shaped head is blunt-fronted like those of some whales. The dorsal fin is smaller and triangular in shape, not swept back like those of the dolphins. The colour of the animal is steel-black above with a pale under-belly. There is a grey patch (which varies in shape and size) on the sides near the head. Another diagnostic feature of the Porpoise is that, although it rolls over to the front as it comes up for air, it does not jump clear of the water surface as the dolphins occaslonally do.

Porpoises are found mainly offshore and venture inshore only when the feeding is particularly good. At certain vantage points on the south and west coasts they can be watched at close proximity on occasions (e.g. Cape Clear Island, Co. Cork).

Occasionally they become isolated in harbours, estuaries and even along some of Ireland's larger rivers. They are some times stranded as a result of these wanderings, and 'beached' animals are not rare. The reasons for strandings among cetacea in general are not fully understood, given the sophistication of their navigational equipment.

The Porpoise is the smallest whale to be found in Irish waters but there have been more than twenty other species recorded including the largest of all animals, the Blue whale. Most of them are irregular visitors in small numbers but some, like the Killer whale, are regular off the western coast.