Speaking the language of the bottlenoses

Long ago, as this newspaper's economic development correspondent, I wrote a big feature on the Shannon Estuary, outlining its potential for deep-water industry. Why not, I proposed, pack all the dirty plants of the future along its banks (with hopeful controls, of course, upon their effluents) and keep the rest of the island crystal clean? It was not, perhaps, the most sophisticated thinking, if typical enough of its time. It was also before we knew that the estuary was home to one of the biggest concentrations of bottlenose dolphins on the west coast of Europe. According to the latest count, using photo-identification, no fewer than 113 dolphins use the Shannon, at least for some period of the year.

The figure is remarkably close to those reported from Moray Firth in Scotland (115) and Cardigan Bay in Wales (127). But quite what it means in terms of a dolphin "group" is far from clear, as a new guide to the ecology of the Shannon bottlenoses (see below) has to agree.

The idea of a resident dolphin "group" in this bay or that is common around the Irish coast; it is the way I think of the half-dozen bottlenoses that seem to hang around together between the Killary and Clew Bay. In the Shannon, too, this a typical size of dolphin groups, though they may gather 20-strong when hunting salmon in a strong tidal current.

Food and its concentration are one obvious reason for any animal gathering, but since dolphins, like all cetaceans, have a social ecology, there are other, more complex measures of togetherness. Communication is certainly one: sperm whales are said to respond to each other halfway across the ocean world.

At that rate, the whistles of the Shannon bottlenoses could potentially put them all in contact, as a herd with a definite home range. "Whistling" dolphin species sometimes form large herds of dozens, hundreds or even thousands of animals. They sometimes go in for communal foraging - not so much hunting in a pack as co-operative herding. Just as humpback whales will concentrate swarms of krill by spiralling upwards together, blowing "nets" of bubbles around the crustaceans, dolphins at sea will swim in a line abreast to round up shoals of fish. Ethna once watched a group of about a dozen bottlenose dolphins fishing around a rock off the strand. They ringed the rock and slowly narrowed the circle, driving the fish in tighter and tighter until they pounced on them in a feeding frenzy.

In the Shannon, too, bottlenoses have been seen circling salmon as a group, with individuals taking it in turns to dash through the fish and feed.

Taking turns at anything demands a fair degree of what sociobiologists call "reciprocal altruism" - doing something for another individual in the trust that he'll do something for you later on. Co-operative hunting may, for example, mean the need for babysitters to mind the calves or, in shark-ridden waters, for guards to keep watch against attack.

In the shelter of the Shannon, however, the dolphins' behaviour has seemed to emphasise the great fluidity of their society, with groups coming together and then separating and changing their character in the process.

Like seems to group with like - all mature females or all mothers, all juveniles or all bachelors. This seems far from the stable society needed for any long-term reciprocal trust or for the kind of fixed hierarchy found among land-based mammal groups. Among the Shannon bottlenoses there seem, so far, to be no bullying "alpha males" leading the pack.

Whatever the subtle permutations of dolphin society, it is obvious that underwater sounds are vital to their lives, whether the clicks of their prey-seeking echolocation, or the whistles of communication. As part of a study of the environmental impact on the Shannon crossing of a natural gas pipeline, a state-of-the-art hydrophone has been recording the dolphins' clicks to judge the extent of their use of the upper estuary.

Conversely, it is man-made underwater sounds that worry the Irish Whale and Dolphin Group, whose scientific work has led the way in what we know of the cetaceans around our shores. The group is concerned that the "acoustic pollution" from airguns used in seismic surveys for seabed oil and gas will disrupt cetacean behaviour and even threaten what seems to be the striking recovery in whale and dolphin abundance in Ireland's sanctuary waters.

The group, led by Simon Berrow, has achieved an outstanding balance between biological conservation of the Shannon dolphins and the local development of cetacean-watching as a tourist attraction. But there is a warning in the new guide, written by Dr Berrow with Sarah Ferriss, a professional conservationist, that dolphin-watching could get out of hand.

The estuary is a candidate SAC (Special Area of Conservation), which enables close control of the commercial boat operators. But the number of their trips has risen sharply and the code of conduct agreed as a condition of licence (and marked by the flying of the Saoirse na Sionna flag) is not respected by unaccredited boats, or, very often, by private recreational craft.

The code of conduct is printed in the new guide: "Do not pursue dolphins . . . Do not corral them between vessels . . . No more than three tour boats around the same group of dolphins at any one time . . ." The injunctions are sound but sadly evocative of what the Shannon dolphins may have to cope with.

The guide, The Shannon Dolphins, is available, at £3.50 including p&p, from the Shannon Dolphin and Wildlife Foundation, Merchants Quay, Kilrush, Co Clare. More about the whales and dolphins off west Clare, together with its birds and other marine life, can be found at the Irrus website for marine ecotourism, supported by the Marine Institute, at www.irrus.com (a guide to match it is in local tourist offices).