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For starters I would like to start with one of the most famous of the killer whales Keiko. Alias Free Willy. Some of the scenes are unique in this film such as the scene where Free Willy jumpes over the wall of stone into the open ocean. The photo below is a photo of when they are practicing for the jump. I also have a page of many photographs of the Killer Whale Keiko.

Female killer whales generally attain a body length of 7.0 m and males 8.2 m (Mitchell, 1975). Perrin and Reilly (1984) reported maximum lengths of 8.5 m for females and 9.8 m for males. For the few weighted killer whales maximum recorded mass was 3,100 kg for a 6.35 m female and 4,000 kg for a 6.04 m male (Hoyt, 1981). The blunt head has virtually no distinguishable beak. The relatively and absolutely large ovate flippers are positioned about one-fourth the distance from the snout to flukes and contrast with the sickle-shaped flippers of most delphinids. Males flippers may measure 2 m long (Harmer, 1927) and attain 20% of the body length; females flippers reach 11 to 13% of the body length (Eschricht, 1866). The dorsal fin of adult males is triangular reaching 1.8 m high, whereas in adult females and young males it is smaller reaching 0.9 m and is distinctly falcate. Adult males can be easily distinguished in a pod thanks to their tall dorsal fin, but sexes of free-living adult females and subadult males are difficult to distinguish except urogenital region is seen. Killer whales pigmentation make them easily identifiable on the field. They are dark, usually jet black, dorsally with a well-demarked white venter. The white region typically extends from the entire lower jaw posteriorly, constricting medially between the flippers, then widening slightly and ending just beyond the urogenital region. Continuous with the ventral white area is a lateral flank patch (Mitchell, 1970) that expands dorsoposteriorly above the urogenital region. The ventral side of the flukes are white or light gray. There is a post(supra)ocular white patch. Light-colored areas often are yellowish, especially in animals from the Antarctic (Berzin and Vladimirov, 1982, 1983; Evans et al., 1982), but yellowish coloration also has been reported from the North Pacific (Scammon, 1874; Scheffer and Slipp, 1948); juveniles are more yellowish than adults. A gray or white saddle highly variable in its shape is usually present posterior to the dorsal fin. Melanistic individuals (Scammon, 1874; Scheffer and Slipp, 1948) and partially albinistic animals (Carl, 1960; Scheffer and Slipp, 1948, Cousteau, date?) have been seen in the North Pacific. Individual and geographical variation in the pigmentation pattern exists (Carl, 1946; Evans et al., 1982). Distribution Killer whales have been observed in all oceans and seas of the world (Leatherwood and Dahlheim, 1978). Although reported from tropical waters and the open ocean, they seem to be most abundant in colder waters of both hemispheres, with the greatest abundance within 800 km of major continents (Dahlheim, 1981; Mitchell, 1975). Killer whales inhabiting coastal areas often enter shallow bays, estuaries, and river mouths (Leatherwood et al., 1976). In some areas they occur seasonally, but in other areas they are apparently year-round residents (e.g. eastern North Pacific). In the northeastern Pacific Ocean, killer whales occur in the eastern Bering Sea (Braham and Dahlheim, 1982) and have been documented as far north as the Chukchi and Beaufort seas. Animals seem to be abundant off the coast of Alaska with a population estimate of 286 for the Prince William Sound and southeast waters (Leatherwood et al., 1984). Year-round occurrence has been documented for the intracoastal waterways of British Columbia and Washington State where an estimated 260 whales comprising 30 pods have been reported (Bigg, 1982). In the western North Pacific, killer whales occur frequently along the Soviet coast in the Bering Sea, Sea of Okhotsk (Tomilin, 1957), and off Japan (Kasuya, 1971). Sightings near Hawaii are uncommon (Richards, 1952). Population estimates are not available for the remainder of the North Pacific. In the North Atlantic Ocean, killer whales have been observed off Greenland, Iceland, in the Barents and White seas, and off Novaya Zemlya (Tomilin, 1957). Regular occurrence also is documented off Norway (Jonsgård and Lyshoel, 1970), Great Britain, and Ireland (Fraser, 1974; Harmer, 1927). Reports from the Mediterranean are sporadic (Casinos and Vericad, 1976). In the western North Atlantic, sightings have been noted in the Labrador Sea, and off Nova Scotia, Newfoundland, Canada (Sergeant and Fisher, 1957). Sightings decrease southward along the continental United States (True, 1904). Several sightings of killer whales have been reported from Caribbean waters (Caldwell et al., 1971). There are no population estimates for the North Atlantic. In the southern oceans, killer whales occur to the tip of Tierra del Fuego, South America (Goodall, 1978) and off South Africa (Ross, 1984), but reports decrease northward along the coasts of both continents. They occur at wide intervals in the Indian Ocean. In the South Pacific Ocean, killer whales are recorded from Australia (Bryden, 1978), New Zealand (Baker, 1983) and off the Galapagos Islands (Robinson et al., 1983). In Antarctic waters, they have been recorded as far south as the Ross Sea (Brown et al., 1974, Tomilin, 1957). Their presence has been observed along the edge of the pack ice throughout Antarctic waters (Brown et al., 1974). Despite numerous reports of killer whales in the Southern Hemisphere, details of their distribution, movements, and abundance are not known (Dahlheim, 1981). Form Skin The stratum granulosum and stratum lucidum layers and true keratinization lack in the structure of the epidermis of killer whales, as in several other delphinids (Harrison and Thurley, 1974). Because the epidermis is sloughed rapidly during swimming, the mitotic division rate is rapid and is 290 times that of epidermis from the human forearm (Harrison and Thurley, 1974). On average (n = 7) adult orcas hold 3.6 vestigial facial vibrissae on the right side and 3.7 on the left (Ling, 1977). Skeleton Skeletal system of cetaceans in general (Adapted from Green, 1972) Cranium Even to the untrained eye, the cetacean skull appears quite modified in comparison to other mammals. The external nares have migrated posteriorly to lie above the internal nares. The proximal ethmoid is exposed from above, and the palatine forms a part of the narial wall. The rostrum is most often developed into a slender beak. The maxillae form the major part of the beak and are divided into superior facial and inferior palatine parts by the tooth row. The frontal process of the maxilla is a thin layer of bone spread over the anterior frontal bone and covering most of the lacrimal, reaching the nasal bones and external nares on its medial edge. The premaxillae are elongated bones fitting between the maxillae and extending posteriorly along the length of the snout to bound the external nares laterally. Ventrally, the premaxillae appear as strips of bone on either side of the midline of the snout, extending posteriorly about one-half the length of the snout. The nasal septum, which is attached posteriorly to the mesethmoid crest and the superior edge of the vomer, extends forward between the median faces of the premaxillae. The parietal bones fit between the frontal, the supraoccipital, the squamosal, and the lateral margin of the alisphenoid. They are curved ventrally, helping to form the cranial floor lateral to the alisphenoid. The interparietal is an irregular-shaped bone situated between the frontals, the parietals, and the exoccipital. The frontal bone forms the greater part of the roof and anterior wall of the cranial vault. Except for the stout supraoccipital process, which forms most of the roof of the orbital fossa, this bone is generally thin. The anterior edges of the bone extend under the frontal process of the maxillae. Posteriorly, the bone makes contact with the parietals and interparietals. lnferiorly, it sutures with the outer margin of the alisphenoid. The malar (zygomatic) bones can best be visualized in the ventral view where they are situated beneath the anterior lateral edge of the frontal process of the maxillae in front of the frontal bones. Each forms part of the pterygopalatine fossa and the anterior part of the orbital fossa. The vomer is a flat plate of bone attached posteriorly to the ventral. surface of the basisphenoid and anteriorly to the interpalatine suture. The palatines are situated along the midline just anterior to the pterygoids. The tympanoperiotic (ear capsule) bones vary considerably in their attachment to the cranium. In the Delphinidae, the periotic part of the mastoid is neither wedged into, nor integrated with, the squamosal, and the periotic is separated from the bones of the cranium by an appreciable gap (Purves, 1966). Hyoid The hyoid is well developed, appearing as a pair of U-shaped arcs of bone and cartilage passing below and slightly anterior to the larynx. The most posterior are is formed of basihyal and thyrohyal segmeints. The anterior are is formed of cartilaginous ceratohyals which connect the basihyals to well ossified rod-like stylohyals. The stylohyals attach to the cranium by cranium by cartilaginous ceratohyals which connect the basihyals to well ossified rod-like stylohyals. The stylohyals attach to the cranium by cartilaginous tips. These tips may be separate elements and are sometimes called tympanohyals (Lawrence and Schevill, 1965). Vertebral Column The neck is generally shortened with varying degrees of fusion of the cervical vertebrae. In some species (rorquals, narwhals, white whales and river dolphins) all seven bones remain unfused. In other species (right whales and bottlenosed whales) all the bones fuse to form a single osseous unit. The remainder of the vertebral column is modified by extension, especially in the lumbar area. The total number of vertebrae is quite variable, with the more recent types having the greater number (Slijper, 1962). The caudal vertebrae have well-formed haemal arches (chevron bones), each of which articulates with two vertebral bodies. In addition to forming the haemal arch, the chevron bones also provide a greater surface area for attachment of caudal muscles. Pectoral Girdle The pectoral girdle is made up of left and right scapular bones and the median sternum. The scapulae are broad, flattened, fan-shaped bones. The structure of the sternum, the number of ribs that attach to it, and the number of double-headed ribs varies among species. In general, the thorax and pectoral girdle are structured with enough flexibility that the thorax can collapse considerably during a deep dive (Ridgway et al. 1969). Flipper The forelimbs or flippers have the same basic structure as the pectoral appendages of other mammals but have developed into flat, fin-shaped paddles. The humerus, radius, and ulna have become so shortened that the elbow is located at the body surface (Felts and Spurrell, 1965, 1966). The humerus has a large globular head where it attaches to the scapula, while the distal end is flattened where it joins the ulna and radius. The carpals are identifiable as separate bones, while the metacarpals are not identifiable from the proximal phalanges, especially in the three middle digits. While Tursiops has the usual five digits, some of the cetaceans have a reduction from the basic plan. Pelvic Girdle The pelvic girdle is highly reduced and only the remnants of a pubic bone remain. This short, rod-like bone is embedded in the lateral body musculature, oriented in a longitudinal direction. The bones do not attach to the vertebral column and are generally larger in the male than in the female, serving as an attachment for genital muscles. Orca skeleton data The vertebral formula is reportedly: 7 C, 11 to 13 T, 10 to 12 L, and 20 to 24 Ca, total 50 to 54 (Eschricht, 1866; Nishiwaki, 1972). There are 11 to 13 ribs per side (Eschricht, 1866) with the first six or seven having both capitular and tubercular attachments to the vertebrae and the following attached only by the tuberculum. Ribs 1 through 6 are directly attached to the sternum. Eschricht (1866) reported the phalangeal formula as: I 1, II 4 to 6, III 3 to 4, IV 2 to 3, and V 2, whereas Nishiwaki (1972) reported it as: I 2, II 7, III 5, IV 4, and V 3. Nishiwaki's (1972) higher counts may include the morphologically similar metacarpals as the proximal phalanx of each digit. Ends of phalanges and most carpal elements were composed of cartilage in an adult male examined by Eschricht (1866). Harmer (1927) hypothesized that the accelerated secondary growth of the flippers in maturing males was related to the continued growth of these cartilages. Ness (1967) stated that the degree of skull asymmetry in orcas is low compared with that of other large delphinids. The teeth are relatively large, up to 13 cm in length (Nishiwaki, 1972) and their apices curve inward. Both the mandibular and maxillary aveoli are deep. The teeth are oval in cross-section at the base. Older animals can have extensive wear on the teeth (Caldwell and Brown, 1964). Upper and lower teeth interlock as the jaw is closed. The entire skeleton is basically built on the typical delphinid plan, but is more robust in all aspects. On the skull, the temporal fossa in noticeably large, indicating a large and powerful temporalis muscle for jaw closure. Brain A 521-cm (curvilinear) killer whale had 4,500-g brain (Caldwell and Brown, 1964). According to Ridgway and Brownson (1984) the brains mass of 555-cm long killer whales are estimated to weight 5,617 ± 968 g on average. An encephalization quotient of 2.9 has been estimated (Ridgway and Brownson, 1984; Wood and Evans, 1980). This is relatively low for odontocetes, but Wood and Evans (1980) believe this low number may be biased because of the large size of killer whales and their high body weight (caused by blubber). Digestive system (Adapted from Green, 1972) The digestive system of killer whales is similar to that of other delphinids. Most odontocetes have numerous peg-shaped, single-rooted teeth which are generally much alike (homodont). Since these teeth are modified for holding and not for chewing, the jaw musculature is considered weak when compared to that of other mammals. The lower jaw is attached in such a way as to move only in one plane, and the coronoid process is either highly reduced or completely missing. The odontocete tongue is short and robust with a freely movable tip. Even though whales are usually considered to have little or no gustatory sense, Slijper (1962) reports that taste buds have been described in some species. The mouth cavity is generally long and narrow anteriorly, widening posteriorly to pass into the highly muscular pharynx. Posteriorly, the pharynx passes into the oesophagus which passes through the thoracic cavity and the diaphragm before entering the first of three main compartments of the stomach. This compartment, called the forestomach, is non-glandular and is lined with white and yellow non-cornified squamous epithelium. This chamber is formed as a sacculation of the oesophagus. The second compartment, the main stomach, has a softer velvety lining and is considered homologous to the fundic stomach of other mammals. This is where HCl and pepsinogen are secreted. The next stomach cavity, the pyloric or connecting stomach, also has a velvety lining but is more tubular than saccular in form in most species. There is some enzyme secretion into this part of the stomach. The pyloric stomach passes to the duodenum which also has a large dilation just beyond the pyloric sphincter. This chamber, called the duodenal ampulla, is often mistaken for a compartment of the stomach. The large common bile duct and pancreatic duct drain into the duodenal ampulla. The intestines are quite long. The measured intestines of one killer whale were 54.2 m long (Eschricht, 1866). The tongue of killer whales is protrusible in contrast to that of bottlenose dolphins (Donaldson, 1977). In Odontoceti there is no caecum and no gross delineation into small and large intestines. The liver is generally bilobed and may weigh as much as one ton in larger species of baleen whales. There is no gall bladder, and the hepatic ducts are well developed. The pancreas is generally mammal-like, having from one to several ducts leading from it. Excretory system Cave (1977) found that the reniculi of the kidney in orcas are arranged in contiguous groups of four. The venous return from the kidney differs from that of Hyperoodon as the renicular vein receives directly the intrarenicular and centripetal tributaries and no peripheral venous plexus is formed. Facial anatomy Mead (1975) found that, in general, killer whales facial anatomy differed little from the typical delphinid plan of asymmetrical nasal sacs except that several structures were proportionately smaller in comparison to 14 other species. Blood chemistry The amino acid sequence of the myoglobin of killer whales is more similar to that of Globicephala sp. (i.e. pilot whales) than to the myoglobin of other small delphinids and phocoenids examined (Meuth et al., 1981). Reproductive organs and mammary glands (Adapted from Webster's Whales and Dolphins, 1998.) Over the course of evolution, the cetacean's body has become streamlined to allow efficient movement in water. As a result, most of their external anatomies have reduced in size, internalized, or been lost altogether. Not surprisingly, the cetacean's genitals and mammary glands have also physically modified over time, almost entirely recessing into the internal body tissues. The male's penis, when not erect, hides folded in a "S" shape in the abdomen with its tip within a prepucial slit, while the female's mammary glands, one either side of the genital slit, are also internalized when she is not suckling. The hidden nature of the cetacean's genitalia makes it difficult to distinguish the difference between males and females. The only way to determine the sex of most cetacean is by observing the distance between the genital and anal slits. In females they are close together, often appearing as a single slit. In males, they clearly appear as two separate openings. Some cetacean species exhibit sexual dimorphism in adulthood. In killer whales, males has a taller, straighter, and more conspicuous dorsal fin than the female. Generally, however, there is no difference in color pattern, or overall difference in body shape, between the sexes. Function Cardio-vascular and respiratory functions A lung tidal volume of 46.2 L and a tidal flow of 129 L/s were calculated for a 4.3-m female (Spencer et al., 1967). One captive animal presented an electrocardiogram with no P wave, an inverted T wave, and a simple R wave, the breathing heart rate was 60 beats/min at the surface and declined to 30 beats/min when submerged (Spencer et al., 1967). The O2 capacity of the blood is reported to be moderate for cetaceans in comparison with the much greater O2 capacity of Kogia blood (Lenfant, 1969). Human and bovine antibodies cross-react with similar pituitary hormones of killer whales indicating the presence of both lactotrophs and somatotrophs (Schneyer and Odell, 1984). Thermoregulation Cetaceans deposit most of their body fat into a thick layer of blubber that lies just underneath the skin. This blubber layer insulates the whale and streamlines the body. It also functions as an energy reserve. Killer whales' core body temperature is about 97.5 F (36.4 C). There is a heat gradient throughout the blubber to the skin. Cetaceans circulatory system adjusts to conserve or dissipate body heat and maintain body temperature. Arteries in the flippers, flukes, and dorsal fin are surrounded by veins. Thus, some heat from the blood traveling through the arteries is transferred to the venous blood rather than the environment. This countercurrent heat exchange aids whales in conserving body heat. When they dive, blood is shunted away from the surface. This decrease in circulation conserves body heat. During prolonged exercise or in warm water whales may need to dissipate body heat. In this case, circulation increases to veins near the surface of the flippers, flukes, and dorsal fin, and decreases to veins returning blood to the body core. Excess heat is shed to the external environment. The cetaceans' fusiform body shape and reduced limb size decreases the amount of surface area exposed to the external environment. This helps them conserve body heat. (Sea World Inc., 1993) Echolocation (Adapted from Webster's Whales and Dolphins, 1998.) Echolocation, or sonar (SOund NAvigation and Ranging), is the production of sound in the form of short, broad spectrum burst pulses, or clicks, and the reflection of those sounds off surrounding objects. Sounds are produced by the nasal sacs, focused with the melon. Sounds reflected by the environment (bottom, rocks, congeners or preys) are mainly received with the lawer jaw, and conducted to the inner ear. Then they are coded to be sent to the brain throught the auditory nerve. Toothed whales (dolphins, porpoises, sperm whales, etc.) including killer whales use echolocation to create with reflected sounds analysed by the brain a three dimensional "sonic picture" of their environment. The ability of dolphins to use echolocation to detect shape and size differences of objects is remarkable. Dolphins use this amazingly accurate sound system to detect food sources. Their ability to detect minute size differences enables them to estimate the size of fish they are chasing. They also learn to recognize particular species of fish by their behavior, and by the characteristic echoes rebounding off the fish swimbladders. Coupled with sensitive directional hearing, echolocation has given toothed whales a highly sophisticated sensory mechanism for survival in the water. Ontogeny and reproduction Breeding cycles Breeding cycles seem not to be fixed worldwide with mating and calving seasons often spanning several months. In the northeast Atlantic, mating occurs from late autumn to midwinter (Jonsgård and Lyshoel, 1970). Polygamy undoubtedly exists in killer whales, and there may be some social control of reproduction. Sexual maturity The average size of males at sexual maturity ranges from 5.2 to 6.2 m. An adolescent growth spurt is reported in males from 5.5 to 6.1 m, the time of sexual maturity (Christensen, 1984). Before this, the growth curves from males and females are identical. Harrison et al. (1972) determined from histological examination that a 656-cm individual with testes masses of 3,632 g (right testis) and 2,270 g (left testis) was not mature, and a 724-cm animal with 11,400 g (right testis) and 12,200 g (left testis) testes was sexually mature. An examination of 57 mature males from the Antarctic indicated an average testis length of 55 cm and a width of 22 cm. The average testis mass was calculated at 10,000 g with a maximum mass of 23,100 g (Mikhalev et al., 1981). Females become sexually mature between a length of 4.6 to 5.4 m (Perrin and Reilly, 1984). Some of this variation is geographic with northeastern Atlantic animals representing the low end and Antarctic animals the high end (Perrin and Reilly, 1984). The size of ovaries from mature killer whales are about 10 to 12 cm by 5 to 7 cm (Mikhaley et al., 1981). A female with a 91-cm fetus had a corpus luteum measuring 7.6 by 5.1 cm (Turner, 1872). A progesterone level of 0.2 to 0.4 ng/mL has been recorded for one female (Kirby and Ridgway, 1984). Courtship and mating (Adapted from Webster's Whales and Dolphins, 1998.) Courtship displays and mating in cetaceans are not always directed towards reproduction. Instead, they may simply be a way for animals to greet and bond with one another, or educate. Chasing, nuzzling, rubbing ... even erection and intromission, have been seen in sexually immature males. The sense of smell is used extensively in sexual encounters in other mammalian species. Cetaceans, however, are thought to lack this sense, so instead use behavioral means to determine the sexual status of potential mates. Some sexual activities in killer whales may also be used by males to ward off competitors. While mating a male generally turns belly up under a willing female with its penis erect. A short intromission occur when the male has found the female's genital groove with its very mobile and sensitive penis. Calving intervals and pregnation Estimates of annual pregnancy rates range from 13.7 to 39.2% with the lower estimates probably more reliable; estimates of annual birth rate range from 4 to 5% (Dahlheim, 1981). Estimates of calving intervals range from 3 to 8 years with observational data indicating that the higher estimates are more typical. However, some evidence suggests that the birth rate may be density dependent (Fowler, 1984; Kasuya and Marsh, 1984). The only killer whales to breed in captivity produced calves 19 months apart (Hoyt, 1981). Estimates of the gestation period in the wild differ from the period observed in captivity with 15 months the best current estimate (Perrin and Reilly, 1984). Sex ratios at birth appear to be 1:1, but overall ratio of males to females has been reported at 0.48:1 and 0.83:1 for the northeast Pacific (Balcomb et al., 1982; Bigg, 1982), and 1.34:1 for the Marion Islands (Condy et al., 1978). Embryology Detailed embryology and placenta morphology of killer whales has been described for several fetuses (Guldberg and Nansen, 1894; Turner, 1872). The maximum size of fetuses differs regionally and has been documented as 255 cm for the North Atlantic (Perrin and Reilly, 1984), 274 cm for the North Pacific (Nishiwaki and Handa, 1958), and 250 cm for the Antarctic (Mikhalev et al., 1981). The smallest neonates recorded are 183 cm for the North Atlantic, 228 cm for the North Pacific (Perrin and Reilly, 1984), and 227 cm for the Southern Hemisphere (Ross, 1984). Suckling and weaning Like other mammals, young cetaceans rely on their mother's milk for the first few months of life. Unlike other mammals, however, the cetacean calf might suck milk from its mother. In any case the mother squirts the milk into her baby's mouth, which is wrapped closely around the nipple with the tongue rolled in a tube around the slightly protruded nipple. This prevents milk from escaping into the water, and being wasted. (Adapted from Webster's Whales and Dolphins, 1998, McBain, pers. comm., 1999) Weaning is thought to occur when a calf reaches a length of 4.3 m (Nishiwaki and Handa, 1958) with lactation lasting 12 months (Bryden, 1972). However, calves may be dependent for at least 2 years. Behaviour Swimming and diving Norris and Prescott (1961) stated that, in general, killer whales took 3 to 5 short dives of 10-35 sec duration followed by a longer dive lasting 1-4 min. Erickson (1978), summarizing data collected from two radio-tagged transient killer whales, reported a mean dive cycle of 5.77 min. The cycle consisted of a long dive followed by three or four surface blows of 3-4 sec spaced a mean 21 sec apart. The longest recorded dive was 17 min. Baird and Goodyear (1993), using recoverable time-depth recorders and VHF radio tags, obtained records of 737 consecutive dive profiles for killer whales off Vancouver Island, British Columbia. The maximum depth of dive was 173 m (bottom depth). Velocity during descents and ascents reached 6 m/sec. The maximum recorded depth of dive of a trained killer whale was 260 m (Bowers and Henderson, 1972). Swimming speeds usually are 6-10 km/hr with a maximum of 40 km/hr (Lang, 1966). Aerial and other behaviour Behaviour such as breaching (Fig. 5), spyhopping (Fig. 6), flipper slapping, and lobtailing is common (Jacobsen, 1986). The significance of such behaviour is not known, and occurrence is within various behavioural contexts. Play behaviour is well documented in killer whales (Osborne et al., 1988). In British Columbia (Hoyt, 1990) and Prince William Sound, Alaska (National Marine Mammal Laboratory, unpublished data), killer whales have been documented to rub along the gravel beds of shallow-water beaches. Sound production Killer whales have an extensive repertoire of sounds covering a wide range of frequencies (Dahlheim and Awbrey, 1982). A series of sacs off the nasal passageway is believed to be involved in sound production (Mead, 975; Heyning, 1989). Ford and Fisher (1982), working with free-ranging killer whales, documented dialectal variations in the signals among killer whale pods off British Columbia. The extent of vocal differences may reflect the degree of associations among pods (Ford and Fisher, 1983) and the differences have been used to help determine genealogics. Regional differences in frequency, str

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