Pilot Whale Facts (Globicephala)

Despite their name, pilot whales are not whales at all—they are large dolphins. The common name "pilot whale" comes from an early belief that a pod of whales was led by a pilot or leader. Found in oceans worldwide, the two species are the long-finned pilot whale (Globicephala melas) and short-finned pilot whale (G. macrorhynchus).

Pilot whales and killer whales are collectively known as blackfish, even though they aren't fish (they're mammals) and they aren't necessarily black.

Description

The common names of the two species refer to the relative length of the pectoral fin compared to body length. However, for all practical purposes the two species appear so similar it's hard to tell them apart without examining their skulls.

A pilot whale is dark brown, gray, or black with a pale marking behind the eye, belly patch, genital patch, and anchor-shaped chin patch. The whale's dorsal fin curves backwards. The scientific name refers to the whale's bulbous melon on its head.

On average, long-finned pilot whales tend to be larger than short-finned pilot whales. In both species, males are larger than females. Adult long-finned pilot whale females reach 6.5 m in length, while males may be 7.5 m long. Their mass averages 1,300 kg for females and 2,300 kg for males. Short-finned pilot whale females reach a length of 5.5 m, while males may be 7.2 m in length. Although smaller than long-finned whales on average, a large short-finned pilot whale male may weigh up to 3,200 kg.

Distribution

Pilot whales live in oceans worldwide. There is some overlap in the ranges of the two species in temperate seas, but long-finned pilot whales generally prefer cooler water than short-finned pilot whales. Usually, the whales live along coastlines, favoring the continental shelf break and slope. Most pilot whales are nomadic, but groups live permanently off the coasts of Hawaii and California.

Diet and Predators

Pilot whales are carnivores that prey primarily on squid. They also eat octopuses and several species of fish, including Atlantic cod, blue whiting, herring, and mackerel. They have an unusually high metabolism for deep-diving hunters. Pilot whales sprint to their prey, which may help them conserve oxygen, as they don't have to spend as much time underwater. A typical feeding dive lasts about 10 minutes.

The species may be preyed upon by large sharks, but humans are the principal predator. Pilot whales may be infested with whale lice, nematodes, and cestodes, plus they are susceptible to many of the same bacterial and viral infections as other mammals.

Reproduction and Life Cycle

There are between 10 and 100 pilot whales in a pilot whale pod, although they form larger groups during the mating season. Pilot whales establish stable family groups in which offspring remain with their mother's pod.

Short-finned pilot whale females reach sexual maturity at 9 years of age, while males reach maturity between 13 and 16 years. Long-finned females become mature around 8 years of age, while males mature around 12 years old. Males visit another pod for mating, which usually occurs in spring or summer. Pilot whales only calve once every three to five years. Gestation last a year to 16 months for long-finned pilot whales and 15 months for short-finned pilot whales. Female long-finned pilot whales go through menopause. Although they stop calving after 30 years of age, they lactate until about age 50. For both species, the lifespan is around 45 years for males and 60 years for females.

Stranding

Pilot whales frequently strand themselves on beaches. It is believed most individual stranders are diseased, but the exact reasons for this behavior are not well understood.

There are two popular explanations for mass strandings. One is that the whales' echolocation gives erroneous readings in the sloping waters they frequent, so they accidentally strand themselves. The other reason might be that the highly social whales follow a stranded pod mate and become trapped. In some cases, stranded whales have been rescued by taking pod mates out to sea, where their distress calls lure the stranded whales back to safety.

Conservation Status

The IUCN Red List of Threatened Species classifies both G. macrorhynchus and G. melas as "least concern." Because of the extensive distribution of pilot whales, it's difficult to estimate their numbers and whether the population is stable. Both species face similar threats. Hunting of the short-finned pilot whale off Japan and the long-finned pilot whale off the Faroe Islands and Greenland may have reduced pilot whale abundance because of the cetacean's slow reproductive rate. Large-scale strandings impact populations of both species. Pilot whales sometimes die as bycatch. They are susceptible to loud sounds generated by human activity and accumulation of organic toxins and heavy metals. Global climate change may affect pilot whales, but the impact cannot be predicted at this time.

Sources

• Donovan, G. P., Lockyer, C. H., Martin, A. R., (1993) "Biology of Northern Hemisphere Pilot Whales", International Whaling Commission Special Issue 14.
• Foote, A. D. (2008). "Mortality rate acceleration and post-reproductive lifespan in matrilineal whale species". Biol. Lett. 4 (2): 189–91. doi:10.1098/rsbl.2008.0006
• Olson, P.A. (2008) "Pilot whale Globicephala melas and G. muerorhynchus" pp. 847–52 in Encyclopedia of Marine Mammals, Perrin, W. F., Wursig, B., and Thewissen, J. G. M. (eds.), Academic Press; 2nd edition, ISBN 0-12-551340-2.
• Simmonds, MP; Johnston, PA; French, MC; Reeve, R; Hutchinson, JD (1994). "Organochlorines and mercury in pilot whale blubber consumed by Faroe islanders". The Science of the Total Environment. 149 (1–2): 97–111. doi:10.1016/0048-9697(94)90008-6
• Traill T. S. (1809). "Description of a new species of whale, Delphinus melas". In a letter from Thomas Stewart Traill, M.D. to Mr. Nicholson". Journal of Natural Philosophy, Chemistry, and the Arts. 1809: 81–83.