Globicephala melas

25.

Long-finned Pilot Whale

Globicephala melas

French: Globicéphale noir / German: Langflossen-Grindwal / Spanish: Calderén de aleta larga

Other common names: Atlantic Pilot Whale, Caaing Whale, Common Blackfish, Common Pilot Whale, Northern Pilot Whale, Pothead Whale; North Atlantic Long-finned Pilot Whale (melas); Southern Long-finned Pilot Whale (edward)

Taxonomy. Delphinus melas Traill, 1809,

“in Scapay Bay, in Pomona, one of the Orkneys,” Scotland, UK.

Taxonomy of G. melas is currently in dispute. It currently consists of two subspecies, a northern form (melas) and a southern form (edwardii), but full species status has also been argued for these taxa.

There is also some morphological evidence that the northern form itself may consist of two forms, north-eastern and north-western, which are geographically segregated by gyre currents of the North Atlantic Ocean. Skulls from Japan indicate that a subspecies (as yet unnamed) existed in north-western Pacific Ocean from the 8" to the 12" centuries. Two subspecies recognized.

Subspecies and Distribution. G.m.melasTraill,1809—NAtlanticOceannofartherSthanapproximatelytheTropicofCancer,includingtheBarentsSea,WMediterraneanSea,NorthSea,andGulfofSaintLawrence.

G. m. edwardii Smith, 1834 — circumglobal in the Southern Ocean from 14° S to 68° S.

Descriptive notes. Total length 670 cm (males) and 570 cm (females); weight 2300 kg (males) and 1300 kg (females). Neonates are 170-180 cm long and weigh c.75 kg. Like the Short-finned Pilot Whale (G. macrorhynchus), the Long-finned Pilot Whale has bulbous head; slight, barely visible beak; and deep tailstock. Key feature that distinguishes it from the Short-finned Pilot Whale (and the source of its common name) is pair of very long flippers (18-27% of total body length) that curve to form a pronounced “elbow.” Dorsal fin is falcate, with wide base, and is positioned one-third of body length back from snout. Skin pigmentation ranges from a dark gray or brown to black, with several white or pale-gray patches. These include chest patch between flippers that tapers into midline and extends into another patch in urogenital region; saddle patch behind dorsal fin; and eyebrow streaks. Eyebrow streaks and saddle patch may be connected by thin gray lateral line, creating a “cape” shape. This feature is more common in the “Southern Long-finned Pilot Whale” (G. m. edwardii) in the Southern Hemisphere than the “Northern Long-finned Pilot Whale (G. m. melas) in the Northern Hemisphere. Young sexually immature individuals have paler skin than adults. Like the Killer Whale (Orcinus orca) and the Sperm Whale (Physeter macrocephalus), the Long-finned Pilot Whale is very sexually dimorphic in size, with males largely than females. Males also tend to have more bulbous rostra, larger dorsal fins and flippers, and deepertailstocks than females. Each jaw contains 8-13 pairs of teeth.

Habitat. Coastal and oceanic waters, apparently preferring habitat over continental shelf breaks and slopes. Both the northern and southern subspecies of the Longfinned Pilot Whale have anti-tropical distributions, limited to temperate and subarctic regions and to sea-surface temperatures of 0-25°C.

Food and Feeding. The Long-finned Pilot Whale is a deep diver and generally feeds at depths of 300-1800 m, using echolocation frequencies similar to those of bottlenose dolphins (Tursiops spp.). Foraging dives last an average of 18 minutes. Prey species primarily consist of small cephalopods, but small to medium-sized fish suffice as alternatives. Small cephalopods migrate closer to the surface at night as part of the rising deep scattering layer, and consequently, foraging activity by the Long-finned Pilot Whale tends to be nocturnal. In the western North Atlantic Ocean, the primary prey species of the Northern Long-finned Pilot Whale are northern shortfin squid (/llex illecebrosus), Atlantic cod (Gadus morhua), and Greenland turbot (Reinhardtius hippoglossoides). In the eastern North Atlantic Ocean, primary prey includes European flying squid (Todarodes sagittatus) and various species of armhook squid (Gonatus spp.). Populations of Southern Long-finned Pilot Whales in the Southern Hemisphere appear to feed more exclusively on cephalopods.

Breeding. Mating system of the Long-finned Pilot Whale is likely polygynous. Mating activity can occur throughout the year, but it is most frequent in each hemisphere’s respective spring and summer. Gestation lasts c.12 months. Birth interval of the Longfinned Pilot Whale is one of the longest among cetaceans at 3-5 years. This long span accommodates an unusually long lactation period that lasts c.3 years on average. In an offspring’s later years, lactation is less nutritionally necessary and instead likely plays an important role in reinforcing social bonds. Males reach sexual maturity later (c.12 years) than females (c.8 years). Females live almost twice as long (60 years) as males (30-45 years), and post-reproductive female longevity is common.

Activity patterns. Because of their nocturnal foraging habits, the Long-finned Pilot Whale has a dive profile that alternates between deep (more than 100 m) at night and shallow (less than 16 m) during the day. Surface behavior consists mostly of resting and socializing. Resting is most common at sunrise after a night of foraging and individuals will often raft together in groups. Pairs may synchronize swimming patterns for antipredatory and social purposes. The Long-finned Pilot Whale can be somewhat aerially active, “porpoising” while traveling and spy hopping. Breaching is less common.

Movements, Home range and Social organization. The Long-finned Pilot Whale is highly social and will travel in groups of 20-100 individuals, although groups of more than 1000 individuals have been reported. Large groups consist of smaller social subunits of 10-20 individuals. The Long-finned Pilot Whale has also been observed in mixed-species groups with a variety of other delphinids, the Atlantic White-sided Dolphin (Lagenorhynchus acutus) and the Common Bottlenose Dolphin being most common. Social vocalizations of the Long-finned Pilot Whale have a mean frequency of 4480 Hz, lower than vocalizations of the Short-finned Pilot Whale at 7870 Hz. Photo-identification and genetic studies have indicated a stable, matrilineal social structure similar to that of the Killer Whale. These matrilineal units (matrilines) tend to have a slightly female-biased sex ratio and consist of a matriarch and her immediate kin. Strong natal group philopatry is exhibited by both sexes, males especially. Males will mate during temporary aggregations of separate family groups but will otherwise remain in their own matrilines for their entire lives. In the western North Atlantic Ocean, Northern Long-finned Pilot Whales show seasonal inshore—offshore movement. They move toward the edge of the continental shelf from mid-winter to early spring and toward inshore waters of Nova Scotia and Newfoundland, Canada, in summer and autumn. These movements have been correlated with spawning of cephalopod prey species in the region. Long-Finned Pilot Whales occur around the Faroe Islands throughout the year, with peak abundance in late summer. They are among the species most often associated with mass strandings, which are especially common at Cape Cod, Massachusetts, USA, in October—January. This behavior is poorly understood because mass-stranded individuals usually appear physically healthy (single strandings are more often associated with pathological problems), and they may restrand themselves after being assisted off a beach. If the Long-finned Pilot Whale can attune to the earth’s magnetic field to assist in navigation, they may be driven astray by geomagnetic anomalies. Because of their strong social bonds, a group may follow a confused, diseased, or injured individual that has made a navigational mistake.

Status and Conservation. CITES Appendix II. Classified as Data Deficient on The IUCN Red List. Neither subspecies of the Long-finned Pilot Whale has been assessed, but the subpopulation in the Mediterranean Sea is listed as Data Deficient. Abundance of the Long-finned Pilot Whale is ¢.200,000 individuals in Antarctic waters, c.13,000 individuals off eastern Canada, and ¢.780,000 individuals in the eastern North Atlantic Ocean. Overall population trend of the Long-finned Pilot Whale is unknown, but probable declines driven by a combination of threats suggest a 30% reduction in global population size over the next three generations (72 years). The most serious threats are direct and incidental catch. Stable social structure of the Long-finned Pilot Whale has made them easy to herd and ideal hunting targets. Harvesting of the Northern Long-finned Pilot Whale takes place currently off the Faroe Islands and Greenland only, but drive fisheries historically operated off Newfoundland (Canada), Cape Cod (USA), Norway, Ireland, Scotland, and the Falkland Islands. From 1947 to 1971, drive fisheries off Newfoundland killed 54,000 individuals, but this population is now thought to be recovering. There has been large-scale whaling off the Faroe Islands since the 9" century, and annual records dating from 1584 show an average catch of 850 ind/year. Despite this catch rate, the Faroe Islands fishery is considered to be sustainable. Meat, blubber, and oil are the primary commodities. The Long-finned Pilot Whale is also vulnerable to incidental catch in other fisheries, and it seems especially susceptible to entanglement in driftnets. Effects of mortality related to incidental catch have not been quantified. In waters off the north-eastern USA, the Northern Long-finned Pilot Whale is commonly taken in mackerel, herring, and squid fisheries operating over the continental shelf break. Reported takes in the USA do not exceed legally allowable annual quotas, but documented takes likely underestimate actual numbers. In British waters, incidental takes of Northern Long-finned Pilot Whales are common in gillnet, purse-seine, and trawl fisheries operating off south-western Britain, and they have been linked to strandings in the region, which have increased significantly since the 1970s. Incidental takes also occur in fisheries operating in the Mediterranean Sea and off Hawaii. There are few reports of incidental catch in the Southern Hemisphere, but the Southern Long-finned Pilot Whale may be susceptible to driftnet fisheries that target sharks off southern Brazil. Environmental contaminants are also a major threat. In the North Atlantic Ocean, populations of Northern Long-finned Pilot Whales are heavily contaminated with various organochlorine compounds, including PCBs and DDT. Populations off the Faroe Islands are also exposed to high levels of heavy metals, mainly cadmium and mercury, which have bioaccumulated in prey species. These contaminants are known to cause pathological problems, such as immunosuppression and reproductive failure, in other marine mammal species, but such issues have rarely been reported for the Long-finned Pilot Whale. Other threats include noise disturbance from military sonar and seismic surveying, ship strikes, overfishing of prey species, live capture for marine parks, and effects of climate change on habitat and prey availability.

Bibliography. Amos et al. (1993), Baird et al. (2002), Baraff & Asmutis-Silvia (1998), Bernard & Reilly (1999), Bloch & Lastein (1993), Bloch et al. (2003), Borrell & Aguilar (1993), Caurant & Amiard-Triquet (1995), Fullard et al. (2000), Gannon et al. (1997), Heide-Jorgensen, Bloch et al. (2002), Jefferson et al. (2008), Leeney etal. (2008), Nielsen et al. (2000), Olson (2009), Ottensmeyer & Whitehead (2003), Reeves et al. (2003), Senigaglia et al. (2012), Taylor et al. (2008b), Wang & Yang Shihchu (2007).