Megaptera novaeangliae
Creators: name: Russell A. Mittermeier
name: Don E. Wilson
Publisher: name: Lynx Edicions
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Cetacea
Balaenopteridae
Megaptera
Megaptera novaeangliae

description: 8.
Humpback Whale
Megaptera novaeangliae
French: Rorqual a bosse / German: Buckelwal / Spanish: Yubarta
Other common names: Bunch Whale, Hump Whale, Hunchback Whale
Taxonomy. Balaena novaeangliae Borowski, 1781,
“de la nouvelle Angleterre,” (coast of New England, USA).
Although there are no officially recognized subspecies, molecular evidence supports recognition of distinct populations in different ocean basins. Monotypic Distribution. Cosmopolitan, found in all oceans of the world, but with only rare incursions into the Mediterranean Sea.
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Descriptive notes. Total length 1500-1700 cm; weight 30,000-34,000 kg. Adult female Humpback Whales are 40-70 cm longer than males. Mean lengths of physically mature males and females are 1300 cm and 1390 cm, respectively, while mean lengths at sexual maturity are 1180 cm and 1190 cm. The Humpback Whale is relatively shorter and stouter than any other species of rorquals and has a distinct countershading color pattern. Dorsal side of body is uniformly black, and ventral surface can be variably colored, ranging from black to white or mottled black and white. Some populations display an extension of white coloration up flanks. Underside of pectoral flipper typically is white, and color on dorsal surface can vary from all black in most Southern Hemisphere individuals to all white in most Northern Hemisphere individuals. Both lower lips are a uniform black and lack coloration asymmetry of the Fin Whale (B. physalus) and Omura’s Whale (B. omurai). Head of the Humpback Whale is relatively large, 28-30% oftotal body length. External surface of rostrum has a single, low, median ridge that is generally obscured by a series of fleshy knobs (dermal tubercles) that are spaced along it from blowholes to tip of snout. From above, lateral margin of rostrum of the Humpback Whale is slightly convex and intermediate in shape between the broadly U-shaped rostrum of the Blue Whale (B. musculus) and the more sharply pointed rostrum of the Fin Whale. In lateral view, rostrum of the Humpback Whale has a distinctly flattened profile. Dorsal fin is relatively small (up to 30 cm tall) and variably developed, ranging from low and blunt to sharply falcate. Dorsal fin is positioned slightly more than two-thirds the distance between tip of rostrum and flukes and is often located on a low fleshy hump. Pectoral flipper is remarkable in size, being the largest pectoral appendage of any known animal, living or extinct. Relatively slender pectoral flippers can reach up to 500 cm in length (25-33% of total body length) and have scalloped leading edges marked by fleshy tubercles that often are encrusted with barnacles (most commonly Coronula diadema and Conchoderma awritum). Position of individual tubercles corresponds to locations of bony joints within each flipper. As with all species of rorquals,flipper of the Humpback Whale has only four elongate digits (digit I is lost). The first and generally largest tubercle occurs at the position of the joint between radius and the first bone (metacarpal) of digit II, while the next two tubercles occur at the inter-phalangeal joints along digit II. The large fourth tubercle lies at the level of the terminus of digit II and distal to this, successive tubercles along flipper’s leading edge are located at the inter-phalangeal joints along digit III. Wind-tunnel experiments have shown that scalloped leading edges of flippers of Humpback Whales greatly reduce drag, increase lift, and generally improve performance and maneuverability of these impressive wing-like appendages. Caudal flukes of Humpback Whales are relatively large (compared with those of Sei Whales, B. borealis), the width measuring c.27-33-5% oftotal body length. Long trailing edge of caudal flukes is distinctly serrated and marked by a deep median notch. Serration pattern and color on underside of flukes have been used extensively to identify individual Humpback Whales. As with other areas on body,tips of flukes of Humpback Whales are often encrusted with clusters of barnacles. Flukes typically are marked by numerous linear scars thought to result of unsuccessful attacks by Killer Whales (Orcinus orca). Ventral groove blubber of the Humpback Whale is rather distinct and has only 12-36 relatively wide longitudinal pleats that extend from tip ofjaws to umbilicus. This numberis fewer than recorded for any other species of rorquals. Baleen apparatus of the Humpback Whale consists of individual plates that, like most rorquals, are short and broad, with an average length-to-width ratio typically c.2:1. Largest main baleen plates are 85-107 cm in length. Fringing baleen bristles of the Humpback Whale are intermediate in diameter between the Blue Whale (coarse) and the Sei Whale (fine). Baleen of the Humpback Whale is generally dark gray to black and often has white longitudinal streaks. Baleen laminae in front of rack may be all white to yellowish-white. Nevertheless, there is no consistent asymmetry in baleen coloration as occurs in the Fin Whale. Fringe bristle color of the Humpback Whale varies from dark gray or black to brown, or even white. Number of baleen laminae are 270-400 /side, with older individuals typically having more laminae. Humpback Whales are the slowest swimmers of the rorquals and although capable of short bursts of 25 km/h, their normal cruising speeds are 5-14 km/h. At sea, blowhole and low dorsal fin are often visible at the same time when an individual is surfacing. Blow is relatively low and bushy and generally up to 2-3 m high. When diving, Humpback Whales typically arch their backs high above the water and follow this with raised caudal flukes that display distinctive undersides. The Humpback Whale is well known for its “aquabatics” (in water displays) that can involve full breaches. Although Humpback Whales have many additional unique morphological features relative to other rorquals, molecular studies suggest that they are more closely related to Fin Whales than to other species of rorquals and do not represent a distinct evolutionary lineage separate from the Balaenoptera lineage. For this reason it is questionable whether continued use of the separate generic name, Megaptera, is appropriate.
Habitat. Cosmopolitan distribution and found in all ocean basins. Like most species of rorquals, Humpback Whales undergo long seasonal migrations from low-latitude breeding and birthing grounds to high-latitude feeding grounds. Habitat preferences are difficult to define for highly mobile animals like the Humpback Whale, and they clearly vary with seasons (summer feeding grounds vs. winter breeding and birthing grounds). Management plans generally focus on areas that are currently known to seasonally support significant aggregations of Humpback Whales, such as birthing, resting, and feeding areas and segments of migratory routes. In winter breeding and birthing grounds, water depth appears to be an important limiting factor controlling social organization, with mother—offspring pairs showing a strong preference for waters less than 20 m deep. Such waters characteristically occur near offshore reef systems, islands, channels, and continental shelf areas. Distance from shore seems to be another limiting factor that influences group size and social organization. Larger groups of Humpback Whales are generally found farther from shore than smaller groups. Association of mother—offspring pairs and mother—offspring—escort trios in shallow water and near-shore locations on winter breeding grounds may also reflect a preference of receptive females or females with young for protection from rough seas. In summer feeding grounds, water temperature and position of continental shelf-slope breaks, ice-edge zones, oceanic fronts, eastern boundary currents, and areas of upwelling are limiting factors controlling distribution of nutrients, primary producers, primary consumers,first-order predators, and whales. Although difficult to clearly define as critical habitat, these areas are obviously important to the survival of the Humpback Whale.
Food and Feeding. The diet of the Humpback Whale has been compared with that of the Fin Whale because both species are known to feed on marine invertebrates and vertebrates. This is especially true for populations of Humpback Whales in the Northern Hemisphere where studies of stomach contents of butchered individuals found distinct dietary patterns. Stomach contents often contained a single species of schooling fish, either herring (Chupeaspp.), capelin (Mallotus villosus), sand lance (Ammodytes spp.), or pollock (Pollachius spp.), but others had combinations of various vertebrate prey. Invertebrate prey species found in stomachs of Humpback Whales in the Northern Hemisphere included monotypic or polytypic aggregations of planktonic crustaceans (euphausids, mysids, or copepods) and benthonic species (amphipods). The apparent benthonic feeding strategy exhibited by some foraging Humpback Whales is rare for a species of rorqual and results in some individuals ingesting quantities of sand and gravel—also reported in stomach contents of butchered individuals. More recent studies using stable isotope analysis of biopsy dart samples, in combination with ship-based observation of feeding Humpback Whales in the Bering Sea, suggest a link between prey preference and habitat, with individuals tending to feed on fish in neritic areas and on plankton in deep oceanic waters. Unlike northern populations, Humpback Whales in the Southern Hemisphere appear to feed almost exclusively on pelagic planktonic crustaceans, primarily krill (Euphausia superba). Like all species of rorquals, the Humpback Whale is a lunge-feeder but also has evolved an impressive repertoire of specialized feeding strategies. Perhaps the most unique of these is the practice of bubble-net feeding in which a single individual or, more often, a cooperative grouping of several individuals use bubbles to concentrate schooling fish. A typical cooperative “bubble-netting” event begins with individuals diving to a level below schooling fish, where one individual begins to swim in an ever-narrowing circle while blowing a ring of bubbles. As the curtain of bubbles rises toward the surface, reflections and noise from bubbles scare fish into a tighter grouping, which is made even more concentrated and compact by loud feeding calls made by another individual in the group. When the resulting bait ball is near the water’s surface, the whales ascend through the bubble net and lunge-feed, often breaking the surface in what some observers refer to as a single collective gulp. Such cooperative feeding groups of Humpback Whales are fluid in terms of membership and may number as many as 15 individuals. A variation of bubble netting, called lobtail feeding, has been documented in Humpback Whales feeding in the North Atlantic Ocean and involves an individual slapping the water's surface above a school of fish before diving to blow the bubble screen. Both behaviors are thought to help concentrate prey, and a study that tracked the spread of this unique foraging innovation over 27years concluded that lobtail feeding was being “culturally” transmitted through the population. Humpback Whales also herd prey by using their flukes, pectoral flippers, or both to disturb the water column. Humpback Whales often herd prey toward the water’s surface, which functions as an escape barrier to concentrate prey. There is also some evidence of other forms of cooperative hunting with individual groups of Humpback Whales feeding in formation or using acoustic calls to synchronize feeding lunges.
Breeding. Reproductive biology of the Humpback Whale is probably the best known and most complex of any species of rorqual. Females and males reach sexual maturity at 4-5 years of age, although this figure may be closer to c.8 years in some areas. Female Humpback Whales in the Southern Hemisphere reach sexual maturity at an average body length of 1160-1250 cm and males at 1110-1200 cm. Comparable measurements for the Northern Hemisphere are 1000-1200 cm and 1000-1150 cm, respectively. Reproductive cycle of the Humpback Whale, like most rorquals,is strongly seasonal and in tune with annual migration to low-latitude breeding and birthing grounds. Females come into estrus in winter, and males follow suit by undergoing spermatogenesis and increased testosterone production. Conception primarily occurs during respective austral and boreal winters, with a peak around September in the Southern Hemisphere and February in the Northern Hemisphere. Whaling data, however, suggest that ovulation and successful mating also may occur at other times of the year. Gestation typically lasts 11-11-5 months, with a single young born in the subsequent austral or boreal winter. Although twin fetuses have been reported from butchered pregnant females, live twin births have not been documented. Whaling data also suggest that embryos grow at an average rate of 17-35 cm/month. Young are ¢.390-450 cm in length at birth and weigh 900 kg. Nursing young consume a minimum of 43 kg of milk/day. Young are weaned at 6-10 months on summer feeding grounds when they are ¢.990 cm in length. This suggests an average neonatal growth rate of ¢.3 cm/day. Young often remain with their mothers for up to a year. Females reportedly give birth every 2-3 years, although several examples are known of individual females giving birth nearly annually. Postpartum estrus may occur on a regular basis in Humpback Whales, which may explain male escorts in close company with mother—offspring pairs late in the breeding season. If females were not in estrus, it is unlikely that males would be showing such interest in them. Sex ratio of neonates is essentially 1:1, which probably holds for much of the year except for periods when differential segregation of sexes or sexual classes occurs on or at the ends of the seasonal migrations. On breeding grounds, operational sex ratio is male dominated because males typically remain longer in the area and relative number of fertilizable females is reduced by presence of immature and postpartum females. Both sexes apparently are promiscuous to some extent because paternity tests of young from individually identifiable females show that over successive seasons a given female may mate with several different males. This level of promiscuity calls into question the characterization of the Humpback Whale’s breeding strategy as solely polygynous. Details of the complexity of Humpback Whale’s breeding behavior have emerged from sustained research conducted since the late 1970s in warm waters around the main Hawaiian Islands. Humpback Whales begin arriving by December (some arrive as early as September), with peak abundance in February-March. The last Humpback Whales have usually departed by May, although some individuals remain as late as June in some years. Research suggests that the Humpback Whale practices a mainly polygynous mating system that grossly resembles a lek (males gathering to attract females). Although this mating system does not involve establishment of defensible territories, male Humpback Whales do exhibit aggressive competitive behaviors that include bubble screens, where a whale will forcefully blow bubbles from his blowholes; rear-body thrashing, where a whale throws his tail and peduncle out of the water before smashing it down sideways on the surface; horizontal tail slashing, where whales slash their tails horizontally through the water; and lobtailing, where a whale raises his flukes above the water before bringing them down to forcefully slap the surface. There are times when these aggressive behaviors result in actual physical contact that can lead to injury and,in rare instances, death. Males are also known to form temporary “coalitions” to drive away males in other competitive groups. Besides these male-male competition behaviors, Humpback Whales are also known to perform courtship behaviors that include rubbing or touching one another with their pectoral flippers; “flippering,” where whales raise their pectoral flippers out of the water and slap the surface; head-up displays, where whales horizontally elevate their heads above the surface and then slowly sink without swimming forward; vertical tail extensions, where whales vertically lift their tails out of the water; and escorting, where adult males join with a solitary or, more frequently, a female and her offspring. Vocalization, involving singing males, also plays an important role on the breeding grounds. Individual songs may last for 10-20 minutes, and some solo “performances” that repeat the song over and over may last for several hours or even days. All males in a given area basically sing the same, highly structured song, which consists of several tonal themes or “verses” that are sung in a generally consistent order. The performance appears to be highly ritualized and singers typically assume a motionless posture with head down, tail up, and flukes 7-15 m below the water’s surface. Over the course of the breeding season, the song in a given area evolves as new “verses” are added here and there. Within the context of a modified lek mating system, the song (vocal display) of singing males has been viewed as driven by sexual selection to attract females or dissuade competing males. This hypothesis suggests that the song provides some indication of the fitness of the singer. Although only adult male Humpback Whales sing, males and females produce a variety of different types of non-song vocalizations on breeding (and feeding) grounds and during migration. Other than mother—offspring pairs, the most stable social group among Humpback Whales on breeding grounds is a mother—offspring pair with an adult male escort. This group may remain together for hours or even days, and the escorting male typically remains within a body length of the female and appears to synchronize his breathing and dive patterns with hers. There are also tactile interactions where the male will touch the female with his pectoral flippers. Studies in the Hawaiian breeding grounds of the Humpback Whale suggest that as many as 86% of mother—offspring pairs in a given season have been accompanied by an adult male escort. These interactions generally occur later in the breeding season after some of the postpartum females have come into estrus. Studies of growth layers formed in wax plugs taken from external ear canals of dead Humpback Whales suggest that they may live up to 48 years.
Activity patterns. Daily activity patterns have been described for Humpback Whales on summer feeding grounds in both hemispheres and consist of foraging individuals generally following the diel movements cycle of their prey (deep water during the day and shallow water at night). Like most species of rorquals, annual activity patterns of Humpback Whales are primarily related to migration between summer feeding grounds and winter breeding and birthing grounds.
Movements, Home range and Social organization. Migratory patterns, breeding and feeding areas, and population structure of the Humpback Whale are probably better known than for any other species of rorquals. A number of factors combine to provide this increased level of understanding including its general near-shore migratory routes; its preference for breeding areas near islands, banks, and reefs; and its preference for feeding areas near shelf-slope breaks, regional marine embayments, or channels. Slower swimming speed of Humpback Whales and its affinity for exuberant aquabatics make it easier to study directly. The Humpback Whale holds the record for the longest known migration of any mammal. In support of this claim is the report of a group of seven whales (including a young) that traveled from the tropical North Pacific breeding and birthing area off Costa Rica and Panama to feeding grounds around Antarctica, a distance of more than 8300 km. Another example of long distance migration involves the well-defined migration route of Humpback Whales between summer feeding grounds in Alaskan waters and winter breeding and birthing grounds in warm waters around Hawaii, a distance of ¢.4830 km. There are several accounts of photo-identified individuals completing this crossing in as few as 36 days, which translates to an average swimming speed of 134 km/day or an average of 5:6 km/h. In the North Pacific Ocean, Humpback Whales feed during summer in waters from the Chukchi Sea south to Honshu in the west and southern California in the east. Their winter migration takes them to three primary breeding and birthing grounds: western subtropical to tropical waters off southern China, Taiwan, and the Philippines east to the Marshall Islands; waters around the main oceanic islands of the Hawaiian archipelago; and warm waters off the southern tip of Baja California, the Revillagigedo Islands, and adjacent mainland Mexico. In the North Atlantic Ocean, Humpback Whales feed during boreal summer in waters as far north as the Labrador Sea, Greenland Sea, and Barents Sea, and as far south as the Gulf of Maine in the west and Ireland in the east. Primary boreal winter migration routes in the North Atlantic Ocean take Humpback Whales to breeding and birthing grounds in the West Indies around Hispaniola (19° N). A small number of Humpback Whales also visit breeding grounds around the Cape Verde Islands (15°-17° N). The likelihood of at least a third, currently unknown, breeding and birthing area in the North Atlantic Ocean is suggested by genetic evidence. The population of Humpback Whales in the northern Indian Ocean is blocked from migrating northward during boreal winter by the Eurasian landmass and consequently remains year-round in warm waters of this region from the Gulf of Aden through the Arabian Sea and into the Bay of Bengal. Various populations of Humpback Whales in the Southern Hemisphere spend austral summer feeding in highly productive waters south of the Antarctic Convergence to edge of the pack ice around Antarctica. The International Whaling Commission (IWC) recognizessix latitudinally arranged feeding areas in the Southern Ocean that are visited by southward migrating Humpback Whales beginning in November, reaching a peak in January, and departing entirely by May. During austral winter migration, groups of Humpback Whales move north out of the Southern Ocean to seven primary breeding and birthing grounds that include waters of the western South Atlantic Ocean (coastal waters of Brazil from Natal to Cabo Frio and the Abrolhos Banks), the eastern South Atlantic Ocean (coastal waters from the Gulf of Guinea south to Cape Town), the south-western Indian Ocean (coastal waters of Mozambique and Madagascar), the south-eastern Indian Ocean (coastal waters of north-western Australia), the western South Pacific Ocean (the Coral Sea and tropical waters around Vanuatu, Fiji, and Tonga), the central South Pacific Ocean (French Polynesia and the Cook Islands), and the eastern South Pacific Ocean (Gulf of Panama south to the Gulf of Guyaquil and the Galapagos Islands). Interestingly, breeding grounds in the eastern South Atlantic Ocean and eastern South Pacific Ocean extend into tropical waters north of the Equator—a pattern that is probably related to the strong eastern boundary currents in these areas. Unlike other species of rorquals, Humpback Whales have been the focus of rather intensive fieldwork to determine population structure on feeding and breeding grounds. From this work,it appears that populations of Humpback Whale in the Northern Hemisphere typically come together on common breeding grounds but disperse into separate loosely affiliated groups as they leave for their summer feeding grounds. These migrating subpopulations show a high degree of genetic structure that suggests matrilineal fidelity to particular feeding grounds. During migration, social organization of individual groupsis quite fluid in terms of membership, with individualsjoining and leaving generally small groups on a somewhat regular basis. Population structure on the more communal feeding grounds, however, is probably diffuse, a possible result of male-mediated gene flow among subpopulations arriving from different feeding grounds. Feeding associations composed of multiple individuals tend to be temporary and dependent on constantly varying prey-patch size. Nevertheless, certain feeding associations (e.g. Humpback Whales in the Gulf of Maine) have been reported to be more stable and to last over most of the feeding season. Vocalization in Humpback Whales is a well-known social aspect of their behavior, especially relatively complex songs sung by solitary males on winter breeding grounds. Other forms of vocalization are known, and both males and females have been reported to make calls on summer feeding grounds or during annual migrations. As a form of communication among Humpback Whales, these calls or vocal sounds appear to have specific functions and, in some cases, are restricted to particular social groups. For example, vocal sounds termed “wops” seem to represent a contact call between a mother and her offspring, while “thwops” are thought to be a more general contact call among individuals of no particular gender or age group. A series of grunts or grunt trains has been associated with comingling of groups. Other vocal sounds produced by Humpback Whales include groans, snorts, “crys,” barks, and underwater blows or bubble bursts. Another form of social sounds used by Humpback Whales in communication are surface generated sounds such as those produced by breaching, which appears to communicate location and body size when an individual is leaving or joining a group, or pectoral slapping, which may be a signal from females to nearby males. These surface-generated sounds also increase in frequency when whales are excited and,at times, may represent no more than simple play.
Status and Conservation. CITES Appendix I. Classified as of Least Concern on The IUCN Red List. The subpopulations of Humpback Whales in the Arabian Sea and Oceania are listed as Endangered. This charismatic rorqual species has been assigned a Least Concern category primarily because of the impressive increase in global populations that has occurred since intensive commercial overexploitation ended. Nevertheless, there are certain stocks that continue to remain at low population levels and,if considered on their own, would be assigned to a more threatened status. Causes of earlier global population decline are obvious and well documented in kill records kept by the whaling industry. Shore-based whaling of Humpback Whales began in the 17" century in the North Atlantic Ocean and increased in lethal effect with the advent of pelagic factory whaling. During 10years in the early 20" century (1904-1913), ¢.19,986 Humpback Whales were killed in waters around South Georgia Island, while a little more than ten years later (1926-1935), the number killed declined to only 303 individuals in the same area. This sharp decline demonstrated the unsustainable nature of commercial exploitation of the Humpback Whale and other species of rorquals that was occurring at this time. The most recent population estimate for Humpback Whales in the North Atlantic Ocean from the West Indies breeding and birthing grounds in 1992-1993 was 10,752 individuals, which combined with photoidentification of 72 individuals in the Cape Verde Islands area provided a metric for computing annual rate of increase at 3-1%. Estimates of subpopulations of Humpback Whales on breeding grounds in the eastern North Pacific Ocean off Mexico in 2008 were 6000-7000 individuals, while 2008 estimates for the subpopulation in the western North Pacific Ocean on winter grounds south ofJapan was substantially less at 938-1107 individuals. Breeding grounds around the Hawaiian Islands appear to support the largest subpopulation of Humpback Whales in the North Pacific Ocean (7120-10,425 individuals). Analysis of 1991-1993 population data for the entire North Pacific Ocean suggests a rate of increase of 4-:9% /year. The year-round resident population of Humpback Whales in the northern Indian Ocean (Arabian Sea) is probably the most threatened and, based on photo-identification data, consists ofless than 60 individuals. Populations of Humpback Whales have been relatively well studied in the Southern Hemisphere where as many as seven major breeding stocks are recognized by the IWC. Population assessments have only been completed for three of these stocks (south-western Atlantic Ocean off Brazil, south-eastern Indian Ocean off north-western Australia, and south-eastern Pacific Ocean off Ecuador, Columbia, and Panama), and this work serves as a useful measure of current status of Humpback Whales in the Southern Hemisphere. The subpopulation in the south-western Atlantic Ocean off Brazil, which had been reduced to only a few hundred individuals by the mid-1960s, has made a strong recovery to a population on winter breeding grounds of ¢.6250 individuals based on 2002-2005 data. The population in the south-eastern Indian Ocean has also rebounded from a pre-moratorium level of ¢.1000 individuals to 10,032 individuals in 1999. Humpback Whales on breeding grounds of the southeastern Pacific Ocean were estimated at ¢.2917 individuals in 2003-2004. The current estimate of populations of Humpback Whales in the Southern Hemisphere is ¢.36,400 individuals. As with other species of rorquals, the international moratorium on commercial whaling that began in 1986 represents the primary conservation measure for insuring survival of the Humpback Whale. Ongoing threats are essentially the same as for other species of rorquals and include entanglement in fishing gear (bycatch), fatal encounters with vessels (ship strikes), anthropogenic impacts (commercial shipping noise and whale watching harassment), habitat decline and interference, aboriginal whaling, and “scientific research.” In the latter case,Japan has issued scientific permits for its whaling fleet to engage in lethal sampling of Humpback Whales and has set an annual catch of 50 individuals. As of 2013, Japan has not implemented this plan.
Bibliography. Clapham (1996, 2009), Clapham & Mead (1999), Darling et al. (2006), Ersts & Rosenbaum (2003), Filatova et al. (2013), Fish et al. (2011), Frazer & Huggett (1973), Mercado et al. (2003), NMFS (1991), Reeves, Clapham & Wetmore (2002), Reilly et al. (2008h), Tomilin (1957), Winn & Reichley (1985).
description: Published as part of Russell A. Mittermeier & Don E. Wilson, 2014, Balaenopteridae, pp. 242-299 in Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona :Lynx Edicions on pages 297-299, DOI: 10.5281/zenodo.6596011