No beach pebble unturned in the great seal census

ANOTHER LIFE:IT'S BEEN A WHILE since I communed with a grey seal, if that is the right word for lolling on a rock among sea pinks and exchanging deep, meaningful gazes with a gleaming, black head in the bottle-green swell below, writes Michael Viney.

Raptly busy at this on Caher Island, off Inishturk, the other afternoon, I remembered another such pinniped, in the Blaskets, that waited each day just where I wanted to cast my spinner, willing me to catch another pollack for him to snatch off the hook.

This time, after our own picnic, we set off back to the mainland with banks of sea fog in chilly pursuit. Relentlessly overtaken, our helmsman aligned the bow of the dinghy with the airborne summit of Mweelrea Mountain until this, too, disappeared, leaving only a shimmer of white sun behind us and the slow weave of waves ahead.

We eventually arrived at a strange, but slowly familiar, cliff and groped along the coast, peering at gauzy landmarks and looking down for the dozen or so sharp-edged reefs along this stretch that show up only at low tide. A glassy sea reared up beneath us into long and noisy breakers but admitted us at last to the right spot on the sand.

I offer this summery episode as preface to a new survey (what else?) that had its own island problems in computing the breeding population of the Republic's grey seals. We now know that there are a minimum of 5,509 to 7,083 of all ages, and (this rather more certainly) that a total of 1,574 pups were born during the 2005 breeding season.

A lot of the survey report, available from the National Parks and Wildlife Service, is about methods, but still worth reading. For preparation and coordination, by land, sea and air, the SAS itself couldn't have done much better.

The entire population of grey seals never makes itself available for counting all at once. But between late August and early December they come ashore to moult and have their pups - a window of visibility all too often lashed by rain and wind.

Unlike the smaller harbour seals, hauling out to breed on inshore islands and sand-banks, the greys choose remote, uninhabited islands and deep sea caves, or coves below precipitous and unfrequented cliffs. For 40 years, surveys have been inevitably partial or restricted to a few big island breeding sites, such as the Blaskets, Inishkeas or Saltees. Many breeding sites remained unknown.

In that time, scientists working with grey seals around Britain evolved a formula for relating population to birth-rate: for every pup, apply a multiplier of 3.5 to 4.5 to get the total number of seals (hence the range of the Irish estimate). Digital photography, with its instant, focused zooms and searchable images, brought new capabilities to surveys from the air.

In the 2005 Irish survey, a huge image bank was built up from thousands of digital stills and video tapes made from a high-winged plane and an Air Corps helicopter (this for peering under cliffs and into gullies and caves). There were rules about flying too disturbingly low or near, so that analysing the pictures meant sorting baby seals from white rocks and plastic debris, and dead pups from live ones.

The aerial counts were concentrated in the west, and their reliability tested by simultaneous ground counts at five breeding colonies on islands from Donegal to Cork. On the east coast, from Lambay to the Saltees, the counts were left entirely to ground teams.

Predictably, more than half the Republic grey seals live along undisturbed shores in the west. The much-studied Inishkea group of islands, off north Mayo, still the biggest breeding area, had trebled its pups in a decade. Other sites showed comparatively little change. A surprise was to find almost 30 per cent of the seals using the remote mainland coast of south-west Donegal (think of the coves and caves at the foot of those colossal cliffs at Slieve League), and some 30 new breeding locations have been verified by the survey.

Led by Oliver Ó Cadhla of UCC's Coastal and Marine Resources Centre, the operation was bound to produce the biggest total yet. The first estimate, from 40 years ago - before general European protection of the seals - was 2,500. Research between 1995 and 2000 pushed that to more than 4,000.

The new figures are in line with the graph around these islands that brought Britain's (mainly Scottish) total of grey seals in 2004 to an upper estimate of 153,000. Climate change could produce one new control: a rise in numbers of large sharks that - as already shown in the Western Atlantic - are the grey seal's leading predators. This is, of course, if the Atlantic's fishermen don't kill all the sharks first.

Download the survey from the National Parks and Wildlife Service website at www.npws.ie