Pilot whale (Globicephala melas)

The pilot whale is a large dolphin, black or dark grey in colour, except for a light saddle behind the dorsal fin, and with a bulbous melon on the front of the head. Long-finned pilot whales are found in cold waters of both hemispheres. They live both in coastal and pelagic environments in the North Atlantic waters of Greenland, Iceland, and in the Barents region including the southern portion of Svalbard’s waters during the summer months. Pilot whales are one of the most frequently reported whales in events of mass stranding. Stranding can involve single individuals, but often involves the whole pod.

These large dolphins are black or dark grey in colour, except for a light saddle behind the dorsal fin. They have robust bodies with a thick tailstock that is laterally (side to side) compressed. They have a bulbous melon on the front of their heads. The pilot whales of the North Atlantic are long-finned pilot whales, which have flippers that are about 20% of the length of the body. They have a large, sickle-shaped dorsal fin that is located quite far forward on the body (before the midpoint). Males are significantly longer than females, ranging from five to six metres. Females are 4-4.7 m long, have a much smaller dorsal fin and are less robustly built than males. The blow of pilot whales is short and very diffuse, and they do not show the fluke when they dive. Pilot whales are most easily recognized at a distance by the fact that they are highly social (in combination with their body size and colour), living in pods that range in size from 10 to over 200 animals.

Distribution

Long-finned pilot whales live in cold waters of both hemispheres (while short-finned pilot whales live in tropical and temperate waters). They live both in coastal and pelagic environments in theNorth Atlantic waters ofGreenland,Iceland, and in the Barents region including the southern portion ofSvalbard’s waters during the summer months. Most populations of pilot whales are nomadic with seasonal movements related to the distribution of squid, their favourite prey.

Ecology

There are approximately one million long-finned pilot whales in the North Atlantic and most of these are in the Northeast Atlantic. Pilot whales are highly social and have a social organization similar to killer whales. Pods are quite stable in their composition through time and members of a pod are highly related through maternal lines. Pod size appears to vary geographically, and mean pod size is difficult to determine with certainty in any case because individual pods often aggregate with others for periods of time. Large aggregations composed of hundreds of individuals form at times. Both male and female offspring usually remain within their mother’s pod, likely throughout their lives. But, males mate with unrelated individuals during times when various groups form huge aggregations. Sometimes pilot whales associate with other species of dolphins forming mixed-species groups. Pilot whales are one of the most frequently reported whales in events of mass stranding. Stranding can involve single individuals, but often involves the whole pod. It is not known why these whales (or other species) perform this behaviour. The strong social bonds likely result in the group events, when one whale becomes stranded the others follow. They are highly vocal and have complex acoustic signalling within the social group. Pilot whales feed in a variety of ways, but sometimes form a broad, wide rank only a few animals deep that has been referred to as a ”chorus line”. Maximum diving performance of this species, during trained open-ocean sessions is about 600 m for approximately 15 min; but no information is available from the wild. They feed primarily on squid, but also eat a variety of fish species, including Atlantic cod,Greenland halibut, mackerel, herring and hake. Sources of natural mortality are not well documented for this species. Pilot whales have been observed behaving aggressively toward some other cetacean species, including killer whales.

Life history and reproduction

Females reach sexual maturity around the age of 8 years, while males do not mature until they are approximately 12 years of age. Mating occurs in the spring or early summer, and birthing occurs in late summer or early autumn in the North Atlantic. Pregnancy lasts approximately 12 months for long-finned pilot whales. The calf is nursed for an extended period that can be three years or more. Hence, this species has one of the longest inter-calving intervals among cetaceans. Females can live up to 60 years, whereas males die younger, reaching a maximum of about 45 years of age.

Management status and monitoring

Pilot whales have been hunted in drive fisheries for centuries, which herd a pod into shallow water where they can be killed. In the Faeroes this hunt continues today. In addition, some pilot whales are taken each year in Greenland more or less on an opportunistic basis. Local populations have been reduced substantially by over-harvesting in some areas. Pilot whales are susceptible to entanglement in drift nets. This species is protected in Svalbard.

MOSJ indicators (Environmental Monitoring of Svalbard and Jan Mayen):

Awaiting results from MOSJ…