Whales weigh in for an Irish winter

READERS of the Examiner will have seen Áilín Quinlan’s report of fin whales off the Cork coast.

Accompanied by a feeding frenzy of seabirds, four or five of these enormous creatures have ventured within a mile of land. This is unusual for fins. They prefer deep waters but, according to Nick Slocum of Whalewatch West Cork, this pod came inshore with shoals of spratt.

The fin whale is the second largest animal on Earth.

Females are bigger than males and may be up to 20 metres long.

Some specimens in the south Atlantic reach a length of 24 metres and weigh up to 80 tonnes.

It is a mystery why North Atlantic whales are smaller.

The largest whale of all is the blue; a very big one might be 27 metres long and weigh 130 tonnes.

In 1909, an enormous female was landed at Grytviken, South Georgia. It was 33 metres long and although it was not weighed, it is listed in the Guinness Book of Records as the largest animal ever found.

Blues swim past Ireland on migration. They generally remain well out to sea but 125 of them were landed at the whaling station in Mayo between 1908 and 1922.

Fins and blues are so closely related that they are virtually the same species.

Long ago, whalers claimed the two animals interbred, producing mongrel offspring but the reports were dismissed as old wives’ tales.

Then, in 1983, a whale with characteristics of both species, was washed ashore in Iceland. A post-mortem examination showed the hybrid was sterile and scientists remained confident that, even if mongrel whales were born occasionally, they could never be fertile. Once again, the experts were proved wrong.

In 1986, another freak whale was killed off Iceland. It too was a female. Its sickle-shaped dorsal fin was clearly that of a fin whale, but the plates of its baleen, the great sieve of the lower jaw, were more like those of a blue. A genetic analysis showed the animal’s father had been a fin and its mother a blue.

Then came the bombshell; there was a foetus in its womb. Not only can blue and fin whales interbreed, they can produce fertile hybrids.

Some fin whales are sedentary. Others migrate; a fin tagged off Iceland covered 1,700 kilometres in 10 days. These whales prefer temperate waters, but baby whales are vulnerable to cold. For their sake, the expectant mothers move to warmer regions to give birth.

Our Irish fins probably go to the Canary Islands, where the calves are born in November and December. By summer, the babies are able to cope with the cold and the pods move northwards to sub-Arctic waters.

Whales arriving back from the north in the autumn are often emaciated and starving. It seems they don’t feed very much when in the colder waters or, perhaps, they can’t get enough food. Why, then, don’t they stay in warm waters? It’s another fin mystery.

But the fin whale’s oddest characteristic is the asymmetry of its colour scheme. Symmetry is almost universal in the animal kingdom, although there are notable exceptions.

The garden snail’s shell is not symmetrical, reindeers don’t have matching antlers and some species of crab have a large claw and a small one.

Symmetry seems to be a matter of external appearance; internal organs are not arranged symmetrically. Our hearts, for example, are on the left side of our bodies. Virtually all large wild animals have symmetrical markings, but the fin whale is a spectacular exception. The lower jaw of a fin is white on the right side and grey-black on the left. But why?

Nick Slocum, speaking on RTÉ’s Mooney Show, suggested the odd colour scheme may help the whale to catch fish. Fins are exceptionally fast swimmers, reaching speeds of up to 35km/hour in a short burst. They rush at a shoal of fish, turn on their right side and throw open their huge mouths. Being dark above and white below, a pattern known as counter-shading, makes a hunter less easy to spot. Seabirds and the fish themselves employ this colour scheme. A fin whale on its side is counter-shaded. Up to 20 tonnes of water rush into the mouth, taking the fish with it. The great jaws are then closed and the water pours out through the whale’s baleen, trapping the krill and fish inside the mouth. Perhaps the sudden appearance of the huge dark left jaw as the whale turns, frightens the fish, causing them to flee downwards towards the less visible white side and into the mouth. The fin’s technique has another refinement. When the jaws are wide open, the bones at the front produce a loud bang. This may cause panic among escaping fish, causing them to turn back into the mouth.

Fin whales were slaughtered in their tens of thousands from the mid-19th century onwards. Prior to that, whaling ships were too slow to go after such a fast-moving animal. Though it’s still an endangered species, the fin’s numbers have increased since hunting ceased. Just how many there are in Irish waters is difficult to determine but there must be at least several hundred.