The long-finned pilot whale or pothead whale (Globicephala melas) is a large species of oceanic dolphin. It shares the genus Globicephala with the short-finned pilot whale (Globicephala macrorhynchus). Long-finned pilot whales are known as such because of their unusually long pectoral fins.
Taxonomy and naming
Etymology Pilot whales get their name from the original belief that there was a "pilot" or lead individual in their groups.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. Ridgway, S. H. (1998). Handbook of Marine Mammals: The second book of dolphins and the porpoises. Volume 6, Elsevier. pp. 245–69. The name for the genus, "Globicephala" is derived from a combination of Latin globus ("globe") and Greek kephale ("head"). The specific name "melas" is Greek for "black". This species has also earned the nickname of "pothead whale" in some places because the shape of its head reminded early whalers of black cooking pots.
Taxonomy This species was first classified in 1809 by Thomas Stewart Traill and given the name "Delphinus melas". However, this scientific name was changed later to "Globicephala melaena". Then in 1986, the specific name for this species was reverted to its original form as "melas".
Anatomy and morphology
Size There is sexual dimorphism in the species. Females grow to a maximum length of up to , and a maximum weight of up to . Males are significantly larger at up to in length, and weigh up to . This makes the long-finned pilot whale the second largest member of the dolphin family, behind the orca (Orcinus orca).
Appearance
Despite its common name, the long-finned pilot whale is actually a large species of dolphin. The same is true of orcas and several other small whales. It has a bulbous forehead and is black or dark grey in colour with light-grey or white markings on the throat and belly regions. This light grey patch found on the throat of pilot whales forms the shape of an anchor. Some individuals have other distinct markings such as a light coloured area behind dorsal fin, known as a saddle patch, as well as an upwards sweeping stripe just behind the eye. The dorsal fin is thick and falcate in nature, and is located about a third of the way down the length of the animal. The common name of this species is a reference to the pilot whale's long, sickle-shaped pectoral flippers that are 18 to 27 percent of its total body length.Jefferson, T.A., Webber. M.A., and Pitman, R.L. (2015). Marine Mammals of the World: A Comprehensive Guide to Their Identification (2nd edition). Academic Press: San Diego. Being a toothed whale, pilot whales have a single blowhole.Hooker, Sascha K. (2009). Perrin, William F.; Wursig, Bernd; Thewissen, J.G.M, eds. Encyclopedia of Marine Mammals (2nd ed.). 30 Corporate Drive, Burlington Ma. 01803: Academic Press. p. 1173. .
It can be challenging to tell male and female apart in the wild for many cetacean species. Long-finned pilot whales are no exception, though it was thought in the past that males had hooked dorsal fins while females did not. Recent research on fin shape has shown that this is not a predictable way to distinguish between the sexes. However, males are bigger in size, and relative fin dimensions as well as other characteristics may still be discovered to allow for distinguishing the sex of at least certain age classes for free-ranging pilot whales.
The ranges of long-finned and short-finned pilot whales overlap in some areas of the world. As the difference between them is mainly distinguished by the length of the pectoral flippers and tooth counts, it is hard to tell the two species apart in these areas.ICES (2010). Report of the Working Group on Marine Mammal Ecology (WGMME). 12–15 April 2010, Horta, The Azores. ICES CM 2010/ACOM: 24. 212 pp.
Physiology The long-finned pilot whale has more neocortical neurons than any mammal studied to date, in fact having almost twice as many as humans.
Studies have revealed that the skin of the long-finned pilot whale has self-cleaning abilities. The surface of the skin is covered with tiny ridges (nanoridges), surrounding pores. This structure makes the surface area too small to allow organisms like barnacle larvae to get a good grip. Although the structure is made up of nanoridges, the skin of long-finned pilot whales is still smooth. The space between the ridges is filled with a mucus-like fluid, which may also play a part in self-cleaning. It is most clearly visible on newly shed skin.
Behavior and life history
Social behavior Long-finned pilot whales are very social in nature. They are usually seen in groups, which range in size from a couple of individuals to aggregations of over a thousand.Bloch, D., Desportes, G., Mouritsen, R., Skaaning, S. and Stefansson, E. (1993). An introduction to studies of the ecology and status of the long-finned pilot whale (Globicephala melas) off the Faroe Islands, 1986-1988. Report of the International Whaling Commission. Special Issue 14: 1-32. However, 20 to 150 individuals are more commonly observed. Studies have shown that this species often forms small long-term social units made up of around 8-12 individuals.Jankowski, M. (2005). Long-finned pilot whale movement and social structure: residency, population mixing and identification of social units. M.Sc. thesis, Biology, Dalhousie University. Genetic investigations of the pilot whales driven ashore in the Faroese hunts have shown a relatedness amongst whales, suggesting a matrilineal structure within social units.Amos, B., Bloch, D., Desportes, G., Majerus, T.M.O., Bancroft, D.R., Barrett, J.A. and Dover, G.A. (1993). A review of molecular evidence relating to social organization and breeding system in the long-finned pilot whale. Report of the International Whaling Commission. Special Issue 14: 209-217. This means that calves - females and perhaps the males as well - remain with their mothers for life.
These groups have been observed socializing with common bottlenose dolphins, Atlantic white-sided dolphins and Risso's dolphins. Pilot whales mainly feed on cephalopods, though in certain regions fish may be more prominent in their diet. Northwestern Atlantic whales are thought to dine predominately on short-finned squid.
Long-finned pilot whales can often be seen lobtailing and spyhopping. Occasionally they may also breach. This species is notorious for mass strandings. During a specific time of year, approximately December to March, these whales beach themselves in high numbers along the coast of New Zealand. The reasons for stranding are not fully understood, but because pilot whales have strong social bonds, it is hypothesized that when one animal strands, the rest of the group may have the tendency to follow.
These whales have also been observed babysitting calves that are not their own, with one study showing that many of those doing the babysitting are males.
Communication Long-finned pilot whales make many different kinds of sounds. In addition to squeaks, whistles, buzzes, and other calls likely used for communicative functions, they also produce rapid clicks that function as a type of bio sonar known as echolocation. This allows the whales to "see" in the murky, dark environments that they live in by listening to the nature of the echoes that return.
The whistles and pulsed calls that pilot whales make seem not to fall into distinct types, but rather can be arranged on a continuum.Taruski, A.G. (1979). The whistle repertoire of the north Atlantic pilot whale (Globicephala melaena) and its relationship to behavior and environment. In: Behavior of Marine Animals, Vol. 3: Cetaceans. Edited by: Winn, H.E. and Olla, B.C., Plenum Press: New York, 345-368. These calls are produced in a wide frequency range, which has been observed from less than 1 kHz to about 20 kHz.Nemiroff, L. (2009). Structural variation and communicative functions of long-finned pilot whale (Globicephala melas) pulsed calls and complex whistles. M.Sc. Thesis. Dalhousie University.
Recent studies have found that a large portion of their vocal repertoire is made up of calls produced in repeated sequences.Zwamborn, E. (2016). Repeated call sequences in long-finned pilot whales: social setting, modification, and behavioral context. M.Sc. Thesis. Dalhousie University. These repetitions are more commonly heard when whales are socializing than any other behavioral state (e.g. foraging, traveling, and resting).
Decision-making During the deeper collective dives of groups of long-finned pilot whales, females on the right and left flanks (periphery) are found to lead most often. This may function in a similar fashion to what is observed in cattle drives, where flanking riders are important for maintaining cohesion of the herd of cattle. The study also found that both mature males and juveniles can lead these dives, but that they do so far less often.
Diet Long-finned pilot whales are apex predators, preying on various species of squid, octopus, crustaceans and fish. Examples of fish species recorded as prey include lanternfish, Atlantic herring, silver hake, Atlantic mackerel and spiny dogfish.
Reproduction Females reach sexual maturity at about 8 years of age, while males reach sexual maturity at around 12 years of age. It seems that mating can take place at any time during the year, but it peaks in late spring/early summer for both northern and southern hemisphere populations. Mating is thought to occur when different groups meet up, and breeding within units is a rare occurrence.
Gestation lasts approximately 12 to 16 months and calving occurs once every 3 to 6 years. Calves are generally at birth, and weigh about .NOAA. 2014. Long-finned Pilot Whale (Globicephala melas). http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/pilotwhale_longfinned.htm Most calves are born in the summer, though some calving occurs throughout the year. There is evidence that some males may stay with their mothers after they reach sexual maturity.
Parasites Among other parasites, long-finned pilot whales harbour Crassicauda carbonelli, a species of nematodes which is found exclusively in the penis.
Distribution and abundance
Abundance Though long-finned pilot whales appear to be abundant, there have been no recent reliable estimates for the worldwide population and very little long-term baseline data collected for monitoring population trends. However, based on their apparent abundance and what information is available, they are currently listed by the IUCN as "Least Concern." Conservative estimates for the population found off Newfoundland estimated around 13,000 individuals.Hay, K. (1982). Aerial line-transect estimates of abundance of humpback, fin, and long- finned pilot whales in the Newfoundland-Labrador area. Report of the International Whaling Commission, 32: 475-486. Another study estimated a total of 780,000 animals in the North Atlantic, though this study includes both short and long-finned pilot whales as they are hard to distinguish at sea.Buckland, S.T., Bloch, D., Cattanach, K.L., Gunnlaugsson, Th., Hoydal, K., Lens, S. and Sigurjónsson, J. (1993). Distribution and abundance of long-finned pilot whales in the North Atlantic, estimated from NASS-87 and NASS-89 data. Report of the International Whaling Commission. Special Issue 14: 33-49.
Current distribution