Long-finned Pilot Whale
Common Names: Long-finned pilot whale, Pothead
Irish Name: An píolótach fadeiteach
Key Identification Features
Max body length: Adult c6.2m (20ft), adult c5.4m (17ft)
Average body length: 4m (13ft)
Blow: Strong and bushy, visible in good conditions and quite audible
Head: Bulbous and may overhang the snout on older males
Beak: Almost absent
Dorsal Fin: Unmistakable, large, long at base end and rounded at the tip
Pectoral fin: As the name suggests, they are long, sickle-shaped & pointed at the tip
Colouring / Markings: Black apart from light coloured W shaped patch on throat
Pilot whales, despite their name are the second largest member of the dolphin family and are relatively easy to identify at sea. In field conditions and in any light, they appear jet black or dark grey with no other markings. Pilot whales in Irish waters look very different to any other species; their backward sweeping fin, set well forward on a stocky elongated body is unique and may be sufficient for positive identification. They are highly social, living in tight groups of between 20-80 individuals, but herds of several hundred have been observed.
Species Similar in Appearance
Pilot whales may be confused with Risso's dolphins or killer whales in Irish waters. They can be found associating with other species such as the bottlenose dolphin offshore.
They are a placid, slow moving species and can be seen lob-tailing (slapping tail flukes), spy-hopping (holding head clear of the water, see image above) and logging (resting) on the surface. Juveniles may bow-ride or breach.
Status and Distribution
The long-finned pilot whale is widely distributed in deep pelagic waters from sub-polar to warm temperate regions. However, their "short-finned" relative is found in warmer waters and the two species overlap in places like the Bay of Biscay. The short-finned pilot whale has never been recorded in Irish waters. Pilot whales, like most toothed whales are nomadic in nature, following migrating squid as they move inshore over the continental shelf during summer and autumn.
Where and When Best Seen in Ireland
Being a pelagic, deep water species, it is not surprising that only a handful of inshore sightings exist on the IWDG database, and it is likely that some of these are associated with live- stranding events. They are however frequently observed beyond the continental shelf and over 70% of these sightings are recorded between June and August, which reflects the increase in observer effort on offshore vessels of opportunity in the summer months.
Food and Feeding
Pilot whales feed primarily on squid, but may also prey on fish species such as cod and mackerel. Stomach content analysis of a juvenile 2.9 mt. pilot whale stranded on Red Strand, Clonakilty, Co. Cork in February 2012 was found to have been feeding on mackerel. Resting during the day at the surface, they feed mainly at night when the deep scattering layer rises from the ocean floor to within their diving range. Pilot whales are strong animals with a formidable set of teeth and they may prey upon a variety of deep ocean dwelling squid and fish. Although they form tight groups when on the move or being harassed, once feeding, this rigid formation loosens, which suggests they hunt alone.
Reproduction and Life Cycle
Max life expectancy: 40-50 years
Average life expectancy: 20 years
Female sexual maturity: 6 years
Gestation period: 16 months
Calves born: Late summer
Males sexual maturity: 12-13 years
Pilot whales live in tight family groups comprising adult males and females, related juveniles and calves. These families congregate into larger groups regularly, sometimes on a daily basis. Groups are dominated and led by older breeding adults who direct social, breeding and feeding behaviours.
Humans have long exploited the pilot whale's social characteristics that contribute to their mass stranding, by hunting them at both aboriginal and commercial level. It is believed that some populations may be increasing in the North Atlantic. It is unclear whether pilot whales are affected by conventional fishing practices and they have been observed turning away from drift nets. Hunting of the stock to which pilot whales in Irish waters belong is restricted to the Faroe Islands, where the islanders in a controversial hunt known as the "grind", herd the whales inshore and drive them ashore onto shallow bays, where they are killed and butchered. This hunt may result in the death of significant numbers of pilot whales in any one year, but being opportunistic, there are years when none are killed.
Pilot whales (despite their name) have the dubious distinction of being the species most likely to mass strand, which unfortunately means we have as good a chance of seeing this species dead or dying on our beaches than at sea. Why whole herds of seemingly healthy animals strand remains something of a mystery. The answer lies somewhere in the tight family bonds that bind their social structure. The result of which is that healthy whales may follow an older or sick animal into shallow coastal waters with which they are unfamiliar, or where their echolocation capability which serves them so well in deep water, is found lacking.
Pilot whale live strandings are common occurrences in New Zealand and Australia which both have "stranding flashpoints" where as many as several hundred pilot whales have stranded in a single event. So regular are these events in places like New Zealand's, Cape Farewell spit that Project Jonah devised purpose built rescue pontoons for pilot whales to aid in the re-floating and stabilisation of animals which have been deemed candidates for refloating. A mass stranding occurred in Ireland on the 23 March 2002 in Castlegregory where 18 animals stranded and died. Incidentally this location is just a few miles east of Cloghane, Brandon Bay, where in November 1965 a mass stranding of 65 pilot whales occurred. After locals satisfied themselves that the meat was not for the Kerry palate, the whales were fed to the mink in a local mink farm.