Monday, January 30, 2012
FIN whales are visiting the Celtic Sea between Wexford and Youghal.
According to Pádraig Whooley of the Irish Whale and Dolphin Group, this 80km stretch of coastline offers some of the best whale-watching in the North Atlantic just now.
Although these deep water creatures sometimes approach the shore, they are usually seen from boats. The long thin body is black but the underbelly is white. A pointed snout and tapered head resemble those of a fighter jet and the dorsal fin, which gives the species its name, is positioned well to the rear. Asymmetry is rare in nature, but the right side of the fin whale’s mouth is white or light yellow, while the left side is black. The steamy ‘blow’ is conspicuous; it can rise to a height of six metres.
This is a spectacular creature. Not only is the fin whale the second largest animal alive today, it’s the second largest ever to have lived. Females in the southern hemisphere reach a length of 26 metres and weigh 80 tonnes, although North Atlantic ones seldom exceed 22m. Only the blue whale is bigger; one killed by whalers in 1909 was 33 metres long and was estimated to weigh 190 tonnes. Fin and blue whales just qualify as separate species. They are so closely related that they sometimes interbreed. The offspring of these unions are infertile, but a hybrid female, killed by Icelandic whalers a few decades ago, was said to have been pregnant. It’s thought that there are so few blue whales left that individuals who can’t find partners mate with a fin whale instead.
’Balaena’ is the Latin for ‘whale’, but the term ‘baleen’ refers only to the 11 toothless species. Baleen is a form of keratin, the material of hair and fingernails. Elderly women may remember the corsets which were made from it. Baleen whale foetuses have teeth but they don’t develop. Instead, plates covered with bristles, grow from the upper jaw forming a sieve. There are between 500 and 900 plates in the 70cm-high fin-whale filter. The animal fills its huge mouth with water. Then, closing the jaws, it releases the contents through the baleen, trapping krill fish and copepods inside the mouth.
Fin whales have refined this feeding technique, exploiting the colour difference between the sides of the mouth. At speeds of up to 35km per hour, the whale homes in on a shoal of fish or krill. When about to strike, it rolls onto its right side, opening the huge jaws with a loud bang. The noise frightens the victims and the dark shape of the black left jaws looming above them gives the impression that the attack is coming from above. The fish panic and flee downwards towards the paler lower jaws and are swept into the mouth. Up to a tonne of food is consumed each day.
Like most of the great whales, fins spend the summer months in cool oxygen-rich sub-Arctic waters where fish and plankton are abundant. New-born babies can’t tolerate cold so, in winter, the whales move south to temperate waters to give birth. The single two-tonne calf is born after a year’s gestation. It’s weaned at six months and can breed from the age of six. Not much is known about the fin whale’s social life. The sexes appear to be segregated during migration.
Fin whales, which can travel up to 300km in a day, are such fast swimmers that the old sailing-ship whalers could not out-run them. The arrival of steam ships changed that and whales were slaughtered in their tens of thousands from the mid-19th century onwards. Nor is Ireland blameless where whaling is concerned. According to Professor Tom Hayden, 450 fin whales were landed at the whaling station in Mayo between 1908 and 1914 and 157 were caught between 1920 and 1922. The species seems to have recovered and fin whales are now one of the commoner species off the Irish coast.
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