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. 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 6 m (20 ft), and a maximum weight of up to 2,500 kg (5,500 lb). Males are significantly larger at up to 7.6 m (25 ft) in length, and weigh up to 4,500 kg (9,900 lb). 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. Being a toothed whale, pilot whales have a single blowhole. 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.
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. 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. 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. 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. These calls are produced in a wide frequency range, which has been observed from less than 1 kHz to about 20 kHz. Recent studies have found that a large portion of their vocal repertoire is made up of calls produced in repeated sequences. These repetitions are more commonly heard when whales are socializing than any other behavioral state (e.g. foraging, traveling, and resting).
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