Globicephala macrorhynchus (Gray, 1846)

English: Short-finned pilot whale
German: Kurzflossen Grindwal
Spanish: Calderón de aletas cortas
French: Globicéphale tropical

Family Delphinidae

Globicephala macrorhynchus © Würtz-Artescienza (see "links")

1. Description

The body in pilot whales is robust, with a deep tail stock. The melon is exaggerated and bulbous and the beak is barely discernible or non-existent. The dorsal fin is wide, broad- based, falcate and set well forward on the body. The flippers are long, slender, and sickle-shaped.
A faint grey saddle patch may be visible behind the dorsal fin. A grey midventral line extends to the front into an anchor-shaped chest patch and widens posteriorily to a genital patch. The short-finned pilot whale has a shorter and wider skull than the long-finned species, with the pre-maxillae covering the maxillary bones (Olson, 2009),

Long- and short-finned pilot whales (G. melas and G. macrorhynchus) are difficult to distinguish at sea. However, the species differ, as the name suggests, in flipper length, skull shape and number of teeth. On average, the pectoral fins of the short-finned pilot whales are 1/6 the body length (Olson, 2009). Adult females reach a body length of approx. 5.5 m and males 7.2 m, with a body weight of up to 3,200 kg (Jefferson et al., 2008).

G. macrohynchus appears to vary geographically, but no comprehensive study has been undertaken. Off the Pacific coast of Japan, a northern and a southern population differ sharply in colour pattern and in body size and shape and also in cranial features. However, their taxonomic status remains unsettled (Rice, 1998 and refs. therein; Olson and Reilly, 2002). Water temperature seems to be the primary factor determining the relative distributions of these two populations (Fullard et al. 2000).

2. Distribution

Short-finned pilot whales are found in deep offshore areas and usually do not range north of 50°N or south of 40°S (Jefferson et al. 1993). There is some overlap in range between the two species (Olson, 2009). G. macrorhynchus is probably circumglobal in tropical and warm temperate waters. In the Atlantic it ranges north to New Jersey and to Charente-Maritime in France (it is not present in the Mediterranean); in the Pacific, its range extends north into cooler temperate waters as far as Hokkaido (50°N, 145°W), and Vancouver Island. It is vagrant to the Alaska Peninsula (57°N, 156°W). The southern limits of the range are not fully determined due to past confusion with the G. melas, but G. macrohynchus is known to range south to São Paulo, Cape Province, Western Australia, Tasmania, and Cape Farewell on North Island in New Zealand (Rice, 1998). There is an hypothesis that the short-finned pilot whale is in the process of expanding to fill the former range of long-finned pilot whales in the North Pacific (Bernard and Reilly, 1999 and refs. therein).

Distribution of Globicepahala macrorhynchus (mod. from Taylor et al. 2008; © IUCN):
tropical, subtropical, and warm temperate oceans round the world (Click here for large map).

3. Population size

Olson (2009) summarized population estimates obtained from various researchers via line-transect methods between the 1990's and 2005. In the western Pacific off Northern Japan, the population amounts to 5,300, whereas off southern Japan numbers reach 53,608 (Miyashita, 1993 in Olson, 2009). Dolar (1999) estimated a total of 7,700 individuals in the eastern Sulu Sea (Philippines). Around Hawaii, 8,806 were estimated (Barlow, 2006) and in the Eastern tropical Pacific, the most recent estimate from 2000 gives 589,000 (CV=0,26), with a significant increase of abundance estimates from 1986-1990 to 1998-2000 (Gerrodette and Forcada, 2002). In the US Golf of Mexico, Waring et al. (2007) estimated 2,388, and their best estimate for the western North Atlantic stock is 31,139 whales (CV=0,27). Tenerife's (Spain) resident population of G. macrorhynchus is estimated at 350 individuals (Glen, 2003). However, the current population trend in the Atlantic Ocean is unknown.

4. Biology and Behaviour

Behaviour: Hindell (2008) used sophisticated telemetry logging devices to show that short-finned pilot whales employ energetic sprints to chase down their deep-dwelling prey. These sprints are costly in terms of energy and therefore oxygen, which has to be taken into account in foraging models. Baird et al. (2003), using suction-cup attached time-depth recorders (TDRs) and video camera systems (Crittercam), recorded deep dives at dusk and dawn following vertically migrating prey, and near-surface foraging at night,. The deepest dives recorded (typically 600-800m, max. 27 minutes) were during the day. At night, all whales dove regularly to between 300 and 500m, and the rate of deep (>100m) dives at night was almost four times greater than during the day. Long bouts of shallow (<100 m) diving occurred only during the day. Video footage from the Crittercams during these shallow dive bouts indicated the whales were engaged in social, rest and travel behaviours, but no feeding was documented. Dive-depth differences between day and night presumably reflect vertically migrating prey, though the prey is concentrated at depths of 300-50m during the night.

G. macrorhynchus off Tenerife, Spain, North Atlantic, © Boris Culik

Habitat: The species prefers deep water and occurs mainly at the edge of the continental shelf and over deep submarine canyons (Carwardine, 1995). Davis et al. (1998) found that G. macrorhynchus in the Gulf of Mexico preferred water depths between 600 and 1,000 m.

Schooling: Pods of up to several hundred short-finned pilot whales have been reported, and members of this highly social species are almost never seen alone. Strong social bonds may partially explain why pilot whales are among the species of cetaceans that most frequently mass-strand. Although detailed studies of behaviour have only begun recently, pilot whales appear to live in relatively stable female-based groups (Jefferson et al. 1993).

Three types of social organisation for pilot whale pods off southern California were described: travelling/hunting groups, feeding groups, and loafing groups. The travelling/ hunting groups have also been appropriately described as "chorus lines" as the animals in these are oriented in a broad rank of up to 2 miles in width, but only a few animals deep. Sexual and age-class segregation also have been observed in chorus lines. In the second type of group described, the feeding group, there was sometimes general movement of whales in a given direction, but individuals tend to remain fairly independent of one another. The third type of pod, the "loafing group", was described as an almost stationary aggregation of 12-30 or more individuals, floating at the surface, nearly or actually touching one another. A wide variety of types of behaviour, including mating, was reported to occur in loafing groups (Bernard and Reilly, 1999 and refs. therein).

In the eastern tropical Pacific, approximately 15% of pilot whale sightings include other cetaceans. They are sighted with bottlenose dolphins (Tursiops truncatus) and with tuna-dolphin aggregations (Thunnus albacares and Stenella spp.) and S. coeruleoalba. The most common associate in coastal waters is the common bottlenose dolphin; pilot whales have been sighted also with short-beaked common dolphins (Delphinus delphis), Pacific white-sided dolphins (Lagenorhynchus obliquidens), gray whales (Eschrichtius robustus), fin and sperm whales (Balaenoptera physalus and Physeter catodon) and killer whales (Orcinus orca; Bernard and Reilly, 1999 and refs. therein).

Mazzuca et al. (1999) found that in the Hawaiian Archipelago, short-finned pilot whales stranded in the largest groups and experienced the greatest number of stranding events (x= 14 animals, 5 events) of all cetaceans recorded from 1957 through 1998. The greatest incidence of odontocete mass strandings occurred on the Island of Maui during the month of June. Mass strandings occurred on all the high Hawaiian Islands, except Hawaii; none were reported on the islands or atolls northwest of Kauai. Two-thirds of the events occurred on the leeward sides of the islands with similar bottom topography, coastal configuration, and geomagnetic characteristics in all events.

Mignucci et al. (1999) reported that in waters off Puerto Rico and the US and British Virgin Islands, short-finned pilot whales were one of the most frequently stranded species. A high number of strandings occur in the winter and spring.

Food:l Although they also take fish, pilot whales are thought to be primarily adapted to feeding on squid (Hacker, 1992). They show the tooth reduction typical of other squid-eating cetaceans (Jefferson et al., 1993). Hernandez-Garcia and Martin (1994) found that stomach contents of two short-finned pilot whales found on the Canary Islands were made up entirely of cephalopods: Todarodes sagittatus, Cranchia and juveniles of Megalocranchia.

Mintzer et al. (2008) examined the stomach contents of short-finned pilot whales from the North Carolina coast in January 2005. Brachioteuthis riisei (numerical abundance 28%), an oceanic species, was the most important cephalopod prey, but Taonius pavo (12%) and Histioteuthis reversa (9%) also represented a substantial part of the diet. A large number of otoliths belonging to the fish Scopelogadus beanii were present (25%), indicating that the whales fed primarily off the continental shelf prior to stranding. Stomach content composition differed from those of short-finned pilot whales from the Pacific coast in which neritic species dominate the diet. These findings also suggest that there is a considerable difference between the diet of short- and long-finned pilot whales (Globicephala melas) in the western North Atlantic. The latter feed predominantly on the long-finned squid (Loligo pealei), whereas the former feed on deep-water species.

Reproduction: Females become post-reproductive at around 35 years but may continue to suckle young for up to 15 additional years, suggesting a complex social structure in which older females may give their own or related calves a "reproductive edge" through prolonged suckling. Calving peaks occur in spring and autumn in the Southern Hemisphere and vary by stock in the Northern Hemisphere (Jefferson et al. 1993).

5. Migration

The species appears to be generally nomadic, with no fixed migrations, but some north-south movements are related to prey movements or incursions of warm water. Inshore-offshore movements are determined by spawning squid (outside the squid season, G. macrorhynchus is usually found offshore). Some populations are present year-round, such as in Hawaii and the Canary Islands (Carwardine, 1995).
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A marked seasonality in the distribution of pilot whales has been observed in at least three areas: off southern California; in the eastern tropical Pacific; and off the coast of Japan. In southern California, the seasonal abundance of pilot whales appears to be correlated with the seasonal abundance of spawning squid. E.g. during years of low squid abundance, fewer pilot whales were sighted near Catalina Island. In both the coastal and pelagic waters of the eastern tropical Pacific, the density of population centres appears to change seasonally in response to major changes in the current structure of the area. In the southern California Bight, the occurrence of short-finned pilot whales was associated with high relief topography. There seems to also be a seasonal distribution with depth: pilot whales were found in significantly shallower water during winter (depth 375m) than summer (800m) (Bernard and Reilly, 1999 and refs. therein).

There have been no systematic studies of home range or migration of individuals of this genus. Opportunistic observations in the southern California Bight have indicated that a pod of 20-30 individuals, identified by scars, unusual marks, etc., lived in the area year-round in the 1970's. Following the strong El Niño event in 1982-83, subsequent surveys throughout the 1980s turned up few sightings, and documented the absence of all but one pod of pilot whales near Catalina Island. Shipboard surveys along the entire California coast using line-transect methodology were conducted in 1991 and 1993 within 550km of shore, documenting an apparent return of this stock. The calculated abundance estimate was 1,004 individuals (Shane, 1995; Bernard and Reilly, 1999 and refs. therein).

6. Threats

Direct catch: The short-finned pilot whale has been exploited for centuries in the western North Pacific. The largest catches have occurred off Japan, where small coastal whaling stations and drive fisheries took a few hundred annually (Jefferson et al. 1993). Between 1982 and 1985, 519 of the northern form and 1,755 whales of the southern form were killed. From 1985 to 1989, Japan took a total of 2,326 short-finned pilot whales. This fishery is ongoing: In 1997, Japan recorded a catch of 347 short-finned pilot whales (Olson and Reilly, 2002), which was reduced to 63 specimens in 2004 (Olson, 2009). The current national quota is 50 (Taylor et al. 2008).

Elsewhere, a small, intermittently active fishery takes around 220 pilot whales per year in the Lesser Antilles in the Caribbean at St. Vincent Island, and there are indications of a small fishery at St. Lucia Island (Bernard and Reilly, 1999 and refs. therein).
Dolar et al. (1994) reported on illegal fisheries for marine mammals in central and southern Visayas, northern Mindanao and Palawan, Philippines, where hunters took dolphins and short-finned pilot whales for bait or human consumption. These are taken by hand harpoons or, increasingly, by togglehead harpoon shafts shot from modified, rubber-powered spear guns. Around 800 cetaceans were taken annually.

Incidental catch: There are probably more pilot whales taken incidentally than is presently documented. In US Atlantic waters, pilot whales have been taken in a variety of fisheries, but not exceeding the allowable annual take under US law (Olson, 2009). Based on preliminary data, the squid round-haul fishery in southern California waters is estimated to have taken 30 short-finned pilot whales in one year.

In the California drift gill net fishery between 1993 and 1995, the mean annual take of short-finned pilot whales was 20 (Bernard and Reilly, 1999 and refs. therein). Since the take in US waters exceeded the allowable limit, a take reduction plan was implemented, and currently the annual take is lower than the allowable limit (Olson, 2009).

Forney and Kobayashi (2007) reported two catches in 24,542 observed sets in the Hawaii-based longline fishery, corresponding to about 1-2 casualties per year in this fishery.
In the western Pacific ocean, an estimated 350-750 G. macrorhynchus die annually in passive nets and traps set in Japanese fisheries (Bernard and Reilly, 1999 and refs. therein).

Systematic surveys of 'whalemeat' markets in the Republic of (South) Korea (Baker et al., 2006) using molecular monitoring also revealed products from short-finned pilot whales. As Korea has no programme of commercial or scientific whaling and there is a closure on the hunting of dolphins and porpoises, the only legal source of these products was assumed to be incidental fisheries mortality ('bycatch') as reported by the government to the International Whaling Commission.

In the Caribbean, the most common human-related cause of death categories off Puerto Rico and the US and British Virgin Islands were entanglement and accidental captures, followed by animals being shot or speared (Mignucci et al. 1999).

Pollution: There is a wide variation in contaminant loads in short-finned pilot whales. High concentrations of DDT and PCB were found in whales off the Pacific coast of the USA in the mid 70s, while low levels were found in whales from the Antilles and off Japan (Bernard and Reilly, 1999 and refs. therein). The latter is confirmed by Bustamante et al. (2003), who investigated trace element concentrations in liver, muscle and blubber tissues of two short-finned pilot whales in New Caledonia in the southwestern Pacific and found that values for Al, Cd, Co, Cr, Cu, Fe, organic and total Hg, Mn, Ni, Se, V, and Zn were below levels for concern.

7. Remarks

Range states (Taylor et al. 2008):
American Samoa; Anguilla; Antigua and Barbuda; Aruba; Australia; Bahamas; Bangladesh; Barbados; Belize; Benin; Bermuda; Bouvet Island; Brunei Darussalam; Cambodia; Cameroon; Canada; Cayman Islands; China; Cocos (Keeling) Islands; Colombia; Comoros; Congo; Congo, The Democratic Republic of the; Cook Islands; Costa Rica; Cuba; Côte d'Ivoire; Djibouti; Dominica; Dominican Republic; Ecuador; Egypt; El Salvador; Equatorial Guinea; Fiji; French Guiana; French Polynesia; Gabon; Gambia; Ghana; Grenada; Guadeloupe; Guam; Guatemala; Guinea; Guinea-Bissau; Guyana; Haiti; Honduras; India; Indonesia; Iran, Islamic Republic of; Jamaica; Japan; Kenya; Kiribati; Korea, Democratic People's Republic of; Korea, Republic of; Liberia; Madagascar; Malaysia (Peninsular Malaysia, Sabah, Sarawak); Maldives; Marshall Islands; Martinique; Mauritania; Mayotte; Mexico; Micronesia, Federated States of; Morocco; Mozambique; Myanmar; Namibia; Nauru; Netherlands Antilles; New Caledonia; New Zealand; Nicaragua; Nigeria; Niue; Northern Mariana Islands; Oman; Pakistan; Palau; Panama; Papua New Guinea; Peru; Philippines, Pitcairn; Portugal; Puerto Rico; Saint Helena; Saint Kitts and Nevis; Saint Lucia; Saint Pierre and Miquelon; Saint Vincent and the Grenadines; Samoa; Saudi Arabia; Senegal; Sierra Leone; Singapore; Solomon Islands; Somalia; South Africa; Sri Lanka; Sudan; Suriname; Taiwan, Province of China; Tanzania, United Republic of; Thailand; Timor-Leste; Togo; Tonga; Trinidad and Tobago; Tuvalu; USA; Vanuatu; Venezuela; Viet Nam; Virgin Islands, British; Virgin Islands, U.S.; Wallis and Futuna; Western Sahara; Yemen

G. macrorhynchus is listed as "Data Deficient" by the IUCN, and world-wide only one population, off northern Japan, is currently considered at risk. Insufficient information is available to accurately evaluate the species' status elsewhere (Stacey and Baird, 1994). The species is listed on Appendix II of CITES.

For recommendations on South American stocks, see Hucke-Gaete (2000) (see Appendix 1). See also general recommendations on Southeast Asian stocks in Perrin et al. (1996; Appendix 2).

This species is not listed by CMS, but inclusion in Appendix II is recommended. Recent results indicate a marked seasonality in the distribution of pilot whales in at least three areas: off southern California; in the eastern tropical Pacific; and off the coast of Japan. Range states concerned are the US, Mexico, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, Panama, Columbia, Ecuador and Peru, as well as Russia, Japan, North and South Korea and China.

8. Sources

· Baird RW, Mcsweeney DJ, Heithaus MR, Marshall G (2003) Sub-surface and night-time behaviour of short-finned pilot whales in Hawaii: Information from suction-cup attached time-depth recorders and video camera (Crittercam) systems. Annual Meeting of the European Cetacean Society, Tenerife, Spain.
· Baker CS, Lukoschek V, Lavery S, Dalebout ML, Yong-un M, Endo T, Funahashi N (2006) Incomplete reporting of whale, dolphin and porpoise 'bycatch' revealed by molecular monitoring of Korean markets. Anim Conserv 9: 474-482
· Barlow J (2006) Cetacean abundance in Hawaiian waters estimated from a summer/ fall survey in 2002. Mar Mamm Sci 22: 446-464
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· Bustamante P, Garrigue C, Breau L, Caurant F, Dabin W, Greaves J, Dodemont R (2003) Trace elements in two odontocete species (Kogia breviceps and Globicephala macrorhynchus) stranded in New Caledonia (South Pacific). Environ Pollut 124 : 263-271
· Carwardine M (1995) Whales, dolphins and porpoises. Dorling Kindersley, London, UK, 257 pp.
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· Gerrodette T, Forcada J (2002) estimates of abundance of western/spotted whitebelly spinner, striped and common dolphins, and pilot, sperm and Bryde's whales in the eastern tropical Pacific Ocean. Southwest Fishery Center, La Jolla, California.
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· Hucke-Gaete R ed. (2000) Review on the conservation status of small cetaceans in southern South America. UNEP/CMS Secretariat, Bonn, Germany, 24 pp.
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· Mintzer VJ, Gannon DP, Barros NB, Read AJ (2008) Stomach contents of mass-stranded short-finned pilot whales (Globicephala macrorhynchus) from North Carolina. Mar Mamm Sci 24: 290-302
· Olson P (2009) Pilot whales Globicephala melas and G. macrorhynchus. In: Encyclopedia of marine mammals, 2nd Ed. (Perrin WF, Würsig B, Thewissen JGM, eds.) Academic Press, Amsterdam, pp. 847-852.
. Olson PA, Reilly SB (2002) Pilot whales - Globicephala melas and G. macrorhynchus. In: Encyclopedia of marine mammals (Perrin WF, Würsig B, Thewissen JGM, eds.) Academic Press, San Diego, pp. 898-903.
· Perrin WF, Dolar MLL, Alava MNR (1996) Report of the Workshop on the Biology and Conservation of Small Cetaceans and Dugongs of Southeast Asia. East Asia Seas Action Plan. UNEP(W)/EAS WG. 1/2, Bangkok, Thailand, 101 pp.
· Rice DW (1998) Marine mammals of the world: systematics and distribution. Society for Marine Mammalogy, Spec Publ 4, Lawrence, KS. USA.
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· Taylor BL, Baird R, Barlow J, Dawson SM, Ford J, Mead JG, Notarbartolo di Sciara G, Wade P, Pitman RL (2008). Globicephala macrorhynchus. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1. <www.iucnredlist.org>.
· Waring GT, Josephson E, Fairfield CP, Maze-Foley K, editors. 2007. U.S. Atlantic and Gulf of Mexico Marine Mammal Stock Assessments -- 2006. NOAA Tech Memo NMFS NE 201; 378 p
· Weir CR (2008) Short-finned pilot whales (Globicephala macrorhynchus) respond to an airgun Ramp-up procedure off Gabon. Aquat Mamm 34: 349-354

© Boris Culik (2010) Odontocetes. The toothed whales: "Globicephala macrorhynchus". UNEP/CMS Secretariat, Bonn, Germany. http://www.cms.int/reports/small_cetaceans/index.htm
© Illustrations by Maurizio Würtz, Artescienza.
© Maps by IUCN.