See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/257748539 Right Whale Dolphins Lissodelphis borealis (Peale, 1848) and Lissodelphis peronii (Lacépède, 1804) CHAPTER · JANUARY 1994 CITATIONS READS 5 50 4 AUTHORS, INCLUDING: Koen Van Waerebeek Peruvian Centre for Cetacean … 176 PUBLICATIONS 2,180 CITATIONS SEE PROFILE Available from: Koen Van Waerebeek Retrieved on: 05 February 2016 15 Righ t Whale Dolphins Lissodelphisborealis(Peale, 1848) and Lissodelphis peronii (Lacepede, .804' Thomas A. Jefferson, Michael W. Newcomer., Stephen Leatherwood and Koen Van Waerebeek Genusand Species Taxonomy The genus Lissodelphis(Gloger, 1841) consists of two species of finless dolphins in the family Delphinidae. There is some question as to their validity (Honacki et al., 1982), but at present most researchers regard them as separate species. The right whale dolphins are sometimes classified in a separate subfamily, Lissodelphinae (Fraser and Purves, 1960), but this subfamily designation has not been widely accepted. The genus Lissodelphis has a relatively complicated taxonomic history, reviewed by Hershkovitz (1966) and JeiTerson and Newcomer (1993). Handbook of Marine Mammals, Volome ISBN 0-12-588505-9 335 Copyright@ 1994by Academic PressLtd All rights of reproduction in any form reserved 336 T. A. JEFFERSON ET AL Commonnames The northern right whale dolphin, Lissodelphisborealis, is also referred to as the Pacific right whale porpoise, delfin liso del norte (Spanish), kita semi-iruka Oapanese), severnyi kitovidnyi delfin (Russian), besperyi delfin (Russian), and rett-delphin (Norwegian). The southern right whale dolphin, Lissodelphisperonii, is also called the southern right whale porpoise, mealy-mouthed porpoise, tunina (= tonina) sin aleta (Spanish), delfin liso austral (Spanish), minami semi-iruka Oapanese), dauphin de Peron (French), and yuzhnyi kitovidnyi delfin (Russian). Distribution Range The northern right whale dolphin is a North Pacific endemic (Fig. 1) that is normally distributed from 30° to 500N in the eastern Pacific (Leatherwood and Walker, 1979) and 35° to 51oN in the western Pacific (Sleptsov, 1961; Nishiwaki, 1967). Movements beyond this range occur occasionally, as evidenced by sightings as far south as 29°N off Baja California, Mexico (Leatherwood and Walker, 1979), and as far north as 59°N in the Gulf of Alaska and just south of the Aleutian Islands in the central Pacific (Kajimura and Loughlin, 1988). The northernmost sightings are generally from summer months and the southernmost from winter months. Scammon (1874) reported sightings as far north as the Bering Sea, but there are no other records from north of the Aleutian Islands. Okada and Hanaoka's (1940) report of this species in the "northern sea of Japan" apparently refers to the seas of Japan, in this case the Pacific coast, and not to the Sea of Jap;in proper. Movements south and inshore for winter months and north and offshore for summer months have been reported for both sides of the Pacific (Kasuya, 1971; Leatherwood and Walker, 1979). Peak periods of abundance off southern California coincide with peak occurrence there of market squid (Loligo opalesfens) (Leatherwood and Walker, 1979). The southern right whale dolphin has a circumpolar distribution, generally between the Subtropical and Antarctic Convergences, in the Southern Hemisphere (Gaskin, 1968a; Fig. 1). Northernmost records are from near Pucusana, Peru (12°30'S) off western South America (Van Waerebeek et al. 1991) and from about 23°S off western South Africa (Brown, 1982). The northwardflowing Humboldt (Peru Coastal) and Benguela current systems may allow this cold-water species to extend its range northward in these areas (Brown, 1973, 1982). The southern limit of this species' distribution extends south of the Antarctic Convergence to about 58-610S in some years (Cruickshank and T. A. JEFFERSONET AL 338 Brown, 1981; Goodall and Galeazzi, 1985; Kasamatsu et at. 1988), with the southernmost records from about 64°5 (Brownell, 1974; Kasamatsu et at. 1989). However, the limit of the Antarctic Convergence is highly variable from year to year, and the southern right whale dolphin's distribution likely reflects this. Melliss' (1885) report of the southern right whale dolphin as far north as St Helena (16°00'S, 5°45'W) is considered erroneous (Perrin, 1985), and reports of this species in the North Pacific off japan actually refer to anomalously coloured northern right whale dolphins (Ogawa, 1937; Tobayama et at. 1969). There is some suggestion of inshore and northward summer movements by southern right whale dolphins from sighting records off South Africa (Cruickshank and Brown, 1981); however, Rose and Payne (1991) suggested that southern right whale dolphins may be year-round residents off Namibia, southern Africa. Although the sample size is still small, north of 25°Soff western South America more fresh specimens and sighting records have been registered in july-September than in all other month~ combined, suggesting a northern migration in the austral winter and spring (Van Waerebeek et at. 1991). Habitat Right whale dolphins are observed most often in cool, deep, offshore waters with temperatures of 8-1 9°C (L. borealis,Leatherwood and Walker, 1979) and I-20°C (L. peronii,Cruickshank and Brown, 198); Kasamatsu etal., 1988).They are sometimes seen nearshore, especially where deep water approaches the coast, and the northern speciesapparently prefers "coastal-type" waters in the California Current system (Smith et al., 1986). External Characteristics Colour pattern The major difference between the species is the colour pattern (Fig. 2). The northern species is mostly black, with a white ventral band running from the fluke notch to the gular region; this band widens slightly in the genital area (more so in females than in males: Leatherwood and Walker, 1979) and widens again to cover the entire ventrum between the flippers. There is also a white patch just behind the tip of the lower jaw (Fig. 3), and crescent-shaped patches on the flukes are brushed light grey dorsally and white ventrally (Fig. 4). An uncommonly occurring colour variant, termed "swirled", with more extensive white areas has been reported from both sides of the Pacific (Ogawa, 1937; Tobayama et al. J.969; Leatherwood and Walker, 1979; Black and jefferson, 1992). Southern right whale dolphins are mostly black dorsally and white ventrally. The sharp border between black and white is high on the posterior flank, dips ~ ~ 4) ~ .. 0 ~ '3 :§ '"i§ ~ 4) 4) ~ u :a ,5 ~ ~ 'c 4) '" ~~ ~ 0. .9E..~ ~ " ~ ...j ~ ~ (0$ ::0' ~ . .I::~ uCO ,..,CO (0$0") .1::~~ .~ ~ ~::2 ~ bIJ c ~ "'" 0 .~ '"" ~ ~~ ~ ~ c (0$ '" (0$ .~ ... ~ ~ 'a 0 .~ ",'~ ~~ ~ ~ (0$ .~ ... '" ~ bIJ ,.., ~ (0$ .~ a ,.., .~ .I:: ~ .~ 0 '" a.~ o.'~ <.a, -~ . "0 ~ 0"-; -.I:: ~ ~ RIGHT WHALE DOLPHINS 339 FIG. 2 Lateral views of northern (top) and southern (bottom) right whale dolphins. Photos by F. G. Wood (top) and R. Abel (bottom). 340 T. A. JEFFERSONET AL. FIG. 3 Close-up of the head ofa northern right whale dolphin, showing the short beak, and fine, sharply pointed teeth that are characteristic of the genus. (Photo by M. W. Newcomer.) FIG. 4 Ventral view of the flukes ora northern right whale dolphin. (Photo by M. W. Newcomer.) RIGHT WHALE DOLPHINS 341 lower to the flipper insertion, then sweeps upward and across the melon in front of the blowhole. The beak, anterior melon, and flippers (except for a thin black band on the trailing edges) are white. The dorsal surface of the flukes tends to be dark grey instead of black. Several different types of colour variants have been reported in this species, including those with white spots on the head, those with variations in the extent of black and white on the body and appendages, an animal with a "grey dappled back", an entirely black animal, and a possibly all-white individual (Brown, 1973; Baker, 1981; Cruickshank and Brown, 1981;J. S. Grove, in lit!. 12June 1990; Rose and Payne, 1991). TABLE 1 External measurementsof a northern right whale dolphin neonate (IS 56, California Academy of SciencesAcc. No. 3813), provided by I. Szczepaniak (numbers in parentheses correspond to standard measurements in Norris, 1961) Measurement mm Total length (1) Snout to anterior insertion of flipper (10) Snout to axillary insertion of flipper Snout to external ear (5) Snout to blowhole (9) Snout to eye (2) Length of gape (4) Snout to base of beak (3) Fluke notch to centre of anus Fluke notch to centre of umbilicus Fluke notch to centre of genital opening Fluke span (34) Fluke depth Anterior length of flipper (29) Axillary length of flipper (30) Maximum width of flipper (31) Girth, head Girth, anterior to flipper Girth, posterior to flipper (21) Maximum girth, 435 mm from tip of snout (22) Girth at penis Anal slit length (26) Genital slit length (26) Umbilical slit length Penis length Blowhole length (27) Blowhole width (27) Eye length (24) Ear length (28) 970 285 355 195 145 170 115 20 255 400 325 .145 70 190 130 55 410 410 420 435 280 5 55 30 100 5 20 16 0" 342 T. A. JEFFERSONET AL As in many small cetaceans, calves of both species have been reported to have a muted colour pattern, with brown or grey areas instead of black and white. They attain adult coloration some time in their first year. A 97-cm northern right whale dolphin calf appeared to possess adult coloration (I. Sczcepaniak, personal communication), however this may have been an artefact ofpost-mortem darkening (W. A. Walker, in lit!. 20 May 1990). Size and shape Both speciesof Lissodelphis are characterizedby the completeabsenceof a dorsal fin or dorsal ridge, a slender, dorso-ventrally compressedbody, a straight mouthline, a moderately well-defined, but short beak, small recurved flippers with pointed tips, located about one-quarter of the way back from the snout tip, and small slightly concaveflukes with a deep median notch (Figs 2-4). Both speciesapparently reach lengths of about 3 m; the largest measured specimenswere 3.1 m (L. borealis,Leatherwood and Walker, 1979) and 2.97 m (L. peronii, Van Waerebeek et al., 1991). Males apparently grow larger than females. Previously unpublished external measurementsof a 97-cm northern right whale dolphin neonate (IS 56) are presentedin Table 1. Weight Maximum recorded weight is 113kg for a 282-cmnorthern right whale dolphin (Leatherwood and Walker, 1979)and 116kg for a 25l-cm southern right whale dolphin (Van Waerebeekand Oporto, 1990). Internal Anato~ The following discussion is based on knowledge gained from very few specimens, especially in the case of the southern right whale dolphin. Skull The skull of both species of Lissodelphisis slender and the bones are light {True, 1889; Okada and Hanaoka, 1940; Fig. 5). Skull measurements, previously unpublished, of seven northern right whale dolphins are presented in Table 2. True (1889) could find little to differentiate the crania of these two species. The condylobasallength of the northern species ranges up to at least 474 mm (Table 2), and represents about 2.17 times the width of the skull (Nishiwaki, 1972). Maximum recorded condylobasal length is 441 mm for the southern species (K. Van Waerebeek, unpublished). Baker (1981) considered the skull of the southern right whale dolphin to closely resemble that of the striped dolphin TABLE 2 Skull measurements(in mm) for sevennorthern right whale dol. phin specimens(following Perrin, 1975) US National Museum (USNM) Number Measurement Condylobasallength Rostrum length Rostrum basal width Rostrum width at 3/4 length Rostrum width at ! length Width of premaxillaries at samepoint Tip of beak to blowhole Tip of beak to pterygoid Preorbital width Postorbital width Orbital width Nares width Zygomatic width Greatest width of the premaxillaries Width of braincase acrossparietals Cranial height Cranial length internal Number of teeth UR UL LR LL Tooth row length UR UL LR LL Mandible length R Coronoid length R L Symphysislength R L Post-temporal length R L Post-temporal height R L 290625 290626 8160 286872 270981 286882 286883 436 256 107 474 267 106 33 40 50 60 28 296 309 163* 182 166 54 180 440* 193* 108 416* 224 104 417* 224* 107 427 242 115 420 229 114 37 42 61 54 51 32 317 339 174 188 173 54 193 33 258* 269* 173 192 177 53 192 32 289 294 174 189 172 52 192 33 275 295 175 187 179 52 184 37* 257* 279* 162 180 170 51 184 31 276 292* 166 184 172 53 186 75 81 78 75 82 74 79 160 146 119* 165 139 130 163 138 129 157 136 128 159 135 128 168 140 130 168 135 126 33* 38* 49 48 42 + 3 42 + 3 46 46 42 + 1 43 + 1 48 46 46* 47* 53 51 44* 50* 50 51 48+ 2 50 + I 48+ 1 50 + 2 54 51 51 52 46 55* 55 208 206 217 214 229 224 224 223 170* 147* 207 204 203 202 209 199 187 182* 197 195 174 169 189 188 188 199* 194* 369 369 400 401 376 376 356 356 366 368 346 346 351 350 64 62 71 68 69 68 62 64 65 64 66 68 63 60 45 45 61 60 55 57 61 58 53 5i 50 48 50 51 61 58 68 53 69 60 59 60 65 67 67 65 49 45 70 52 53 54 41 38 49 48 50 47 51 51 * Damaged (measurement or count not accurate). T. A. JEFFERSON ET AL 344 (a) (b) FIG. 5 Northern right whale dolphin skull: lateral view of cranium (a), lateral view of mandibles (b), dorsal view of cranium (c), and ventral view of cranium (d). (Photos by M. W. Newcomer.) (Stenellacoeruleoalba),but to have a shorter, more pointed rostrum.. The rostrum of both species of Lissodelphisis elongated, and tapers to a sharp point (True, 1889; Okada and Hanaoka, 1940; Baker, 1981). The rostral length is slightly more than twice its width (True, 1889; Nishiwaki, 1963, 1972). The premaxillae are widely and progressively separated through to the rostrum tip, and the pterygoid bones are also separated (True, 1889; Okada and Hanaoka, 1940; 345 RIGHT WHALE DOLPHINS (c) (d) FIG. 5 Continued. Baker, 1981). Kasuya (1973) described and illustrated the tympano-periotic complex of the northern right whale dolphin, and noted that its size is most similar to that of Stenella. Fraser and Purves (1960) presented a detailed description of the ventral aspect of the skull of this species. The mandibles of right whale dolphins are long and slender, with a short symphysis (True, 1889; Okada and Hanaoka, 1940; Tomilin, 1957; Baker, 1981). The teeth are small, slender, and sharp, and tooth counts for each jaw are 37-54 (L. borealis, Okada and Hanaoka, 1940; Table 2) and 39-50 (L. peronii, K. Van Waerebeek, unpublished). Nishiwaki (1972) stated that in general there were slightly more teeth in the lower jaw. 346 T. A. JEFFERSONET AL Postcranial skeleton Like the skull, many elementsof the postcranial skeletonof right whale dolphins have been described as light, narrow, or weakly built (Okada and lfanaoka, 1940). Nishiwaki (1963, 1972) reported vertebral counts for the northern speciesof 88-90, with the following formula: Co T 14-15,L29-3o,and Ca37-39; however, Tobayama et at. (1969) gave the formula as Co TI4-lo L29-33,and Ca3.s-40 = 88-92. Characteristic of the delphinids, the atlas and axis are fused. Relative to other speciesof oceanic dolphins (i.e. Delphinusand Stenella),right whale dolphins have a much higher vertebral count, particularly in the lumbar and caudal regions (Okada and Hanaoka, 1940). There are normally 14-17 pairs of vertebral ribs, four to six of which are twoheaded in the northern right whale dolphin (Okada and Hanaoka, 1940; Tobayama et al., 1969), and 13 pairs of vertebral ribs, five of which are twoheaded and one free-floating in the southern species(Baker, 1981).The northern species has 7-10 pairs of sternal ribs (Okada and Hanaoka, 1940; Tobayama et al., 1969) and the southern specieshas eight (Baker, 1981). The sternum is "peculiar in shape", with four lobe-like processes(Okada and Hanaoka, 1940). The phalangeal formula is 11-2,117-8,1115--6, IV3, and V2-3 (Nishiwaki, 1963; Tobayama et al., 1969), but Nishiwaki (1972) subsequently reported nine phalanges in the third digit, which is likely an error. The scapulae are wide relative to their height (True, 1889;Okada and Hanaoka, 1940). Other aspects of the postcranial skeleton are described by Okada and Hanaoka (1940) for the northern, and by Baker (1981) for the southern species. Organs, tissues,andphysiology There has been little work on the soft anatomy and physiology of right whale dolphins. Schenkkan (1973) and Mead (1975) described and illustrated the anatomy of the nasal sac area, and stated that Lissodelphisshows no significant difference from the general delphinid plan. Blubber measurements for both species have been reported to be about 1-2 cm (Scheffer and Slipp, 1948; Leatherwood and Walker'rI979; Baker, 1981). Morejohn (1979) reported a northern right whale dolphin specimen with no evidence of external ear openings. Sharp (1975) studied the electrophoretic and oxygen dissociation properties of 11 northern right whale dolphins, and found that they shared the same haemoglobin form as the Pacific white-sided dolphin (Lagenorhynchus obliquidens). The lipid composition of northern right whale dolphin jaw and melon fats was reported by Litchfield et al. (1975). RIGHT WHALE DOLPHINS 347 Life History and Population Dynamics Growth andreproduction Reproductive data have been published for a total of 11 male and 12 female northern right whale dolphins from the eastern North Pacific (Wick, 1969; Harrison et ai., 1972; Walker, 1975; Leatherwood and Walker, 1979; Sullivan and Houck, 1979; Cowan et ai., 1986). Collectively, these data suggest that males reach sexual maturity at lengths between 212 and 220 cm, and females at about 200 cm. The 114-cm adult female reported by Sullivan and Houck (1979) is an error. The correct length was 164-165 cm and the specimen was not an adult (W. J. Houck, in lilt. 7 March 1990). Miyazaki (1986) summarized data on one 196-cm immature male and 21 females of various lengths from the western Pacific. These data suggest that females reach maturity between 206 and 212 cm. Neonatal length for northern right whale dolphins is unknown, but small calves seen at sea have been estimated to be 80-100cm long (Leatherwoodet ai., 1982), although some very small calves were estimated to be 60-70 cm long (Norris and Prescott, 1961). The calving season is not known, but most sightings of small calves are from winter (Dohl et ai., 1983) or early spring (Leatherwood and Walker, 1979; Leatherwood et ai., 1982). As far as we know, the smallest northern right whale dolphin measured was a 97-cm male stranded in central California on 3 February 1986 (IS 56). This animal still had foetal folds and rostral hairs, but the umbilical remnant had probably been removed by gulls (I. Szczepaniak, personal communication). Almost nothing is known of the reproductive biology of the southern right whale dolphin. Females of 229 cm and 218 cm, and a male of 251 cm were all mature (Baker, 1981; Van Waerebeek and Oporto, 1990). Five pregnant females that stranded in November 1988 had near term foetuses (Cawthorn, 1990), and one stranded in April 1988 had a 102-cm near-term foetus (Van Waerebeek and Oporto, 1990). An intact 86-cm neonate, possibly premature, was recovered from the stomach of a large Patagonian toothfish (Dissostichus eieginoides)(Van Waerebeek et ai., 1991). Mortality Strandings of right whale dolphins are not common (Leatherwood and Walker, 1979; Cruickshank and Brown, 1981), however Woodhouse et al. (1985) reported on the unprecedentedstranding of 23 individual northern right whale dolphins along southern California beachesin 1981. Increasing numbers of southern right whale dolphins have stranded on beachesof north-central Chile in the last few years, but apparently involve mostly by-caught animals discarded from fishing nets (Van Waerebeeket al. 1991). 348 T. A. JEFFERSON ET AL Mass strandings have not been reported for northern right whale dolphins, but a few have been reported for the southern species, including one that involved 77 animals (Fraser, 1955; Goodall, 1978; Baker, 1981; Cawthorn, 1990). Some live-stranded southern right whale dolphins have been returned to sea alive, but it is unknown if they survived (Baker, 1981). There are no records of predatiop for either species, but it is likely that killer whales (Orcinus orca), and possibly large sharks, are at least occasional predators. For the southern species, there may also be other predators, as indicated by the discovery of an intact 86-cm dolphin in the stomach of a 170-cm Patagonian toothfish taken off central Chile in 1983 (Van Waerebeek et at., 1991), and another 87-cm foetus, with the mother's surrounding genital region, in a 360-cm sleeping shark (Somniosuscf. pacificus)from Chile in 1990 (Crovetto et at., 1992). Abundance There are no comprehensive population estimates for either species. Peak populations of northern right whale dolphins have been estimated at 17 800 off southern California (Leatherwood and Walker, 1979), and at around 61500 off central and northern California (Dohl et al., 1983), making them the second or third most abundant cetacean off California, after Delphinus delphis and Lagenorhynchusobliquidens. Preliminary boat surveys and the rapid accumulation of stranding and fishery interaction records in northern Chile suggest that the southern right whale dolphin may be one of the most common cetaceans in this region (Van Waerebeekand Guerra, 1987;Van Waerebeeket al., 1991). Behaviour Social organization Right whale dolphins are highly gregarious. Both species are occasionally seen singly, but more often in groups of up to 2000-3000 for the northern species (Leatherwood and Walker, 1979; Leatherwood et al., 1987) and up to over 1000 for the southern species (Gaskin, 1968b; Cruickshank and Brown, 1981). Average herd sizes for the northern right whale dolphin are about 100 in the eastern Pacific (Leatherwood and Walker, 1979) and 200 or more in the western Pacific (Nishiwaki, 19.72). Mean herd size is 210 individuals for southern right whale dolphins off Chile (Van Waerebeeket al., 1991). RIGHT WHALE DOLPHINS 349 Herd configurations reported for both species are similar (Cruickshank and Brown, 1981) and have been described in detail for the northern species by Leatherwood and Walker (1979). One offour distinct types is usually observed: (I) tightly packed groups, (2) herds with prominent subgroups, (3) Vformations, or (4) "chorus-lines". Feeding Right whale dolphins prey primarily on mesopelagicfishes (especiallylanternfish, family Myctophidae) and squid (Table 3). Both speciesmay dive to depths in excessof 200 m in searchof food (Fitch and Brownell, 1968;Baker, 1981). Associationwith other animals Right whale dolphins have been reported to occur with many other species of marine mammals (Table 4), but are most often seen in association with dolphins of the genus Lagenorhynchus, with which they intermix freely, and with pilot whales (Globicephalaspp.). Swimming and diving Swimming behaviour described for both species is remarkably similar (summaries by Leatherwood and Walker, 1979 for L. borealis,and Cruickshank and Brown, 1981 for L. peronii). Slow-moving groups are undemonstrative, typically exposing only the head and blowhole to respire. Fast-moving herds may employ one of two strategies: (1) swimming just below the surface, rapidly surfacing to breathe, then resubmerging, or (2) swimming rapidly at the surface, where they manifest characteristic low angle leaps and create a considerable surface disturbance (Fig. 6). The long slender bodies of right whale dolphins may allow them to reduce drag by taking several tail strokes while the bulk of the body is out of the water (Au and Weihs, 1980; Norris and Dohl, 1980). Right whale dolphins are fast swimmers, but there have been few direct speed measurements at sea. Reported speeds have been as high as 34 km hr-l for northern (Leatherwood and Walker, 1979) and 22kmhr-1 for southern (Cruickshank and Brown, 1981) right whale dolphins. Individuals have been noted to dive for periods of 10-75 sec, but entire herds have dived for up to 6.25 min (L. borealis, Leatherwood and Walker, 1979) and 6.5 min (L. peronii, Cruickshank and Brown, 1981). Aerial and other behaviour While in the fast-swimming mode, both species have also been seen to perform belly-flops, fluke-slaps,and side-slaps(Fig. 7). Roseand Payne (1991) reported T. A. JEFFERSON ET AL. 350 TABLE 3 Stomach contents of right whale dolphins Prey type Family Species Sources Lissodelphis borealis Squids Fishes Unidentified squid Gonatidae Enoploteuthidae Histioteuthidae Loliginidae Onychoteuthidae Bathylagidae Paralepididae Myctophidae Merlucciidae Scomberesocidae Melamphaidae Centrolophidae 1,2,3 Unidentified gonatids Gonatussp. Abraliopsis sp. Histioteuthis sp. Loligo opalescens (?) Onychoteuthissp. Leuroglossusstilbius Lestidium ringens U niden tified myctophids Symbolophoruscaliforniensis Diaphus theta Lampadenaurophaos Lampa1!Jlctus cr. ritteri Lampanyctusritteri Stenobrachiusleucopsarus Triphoturus mexicanus Ceratoscopelus townsendi Tarletonbeaniacrenularis Merlucciusproductus Cololabis saira Scopelogadus bisPinosus Melamphaeslugubris lcichthys lockingtoni 4 5 5 5 6 Dosidicusgigas Notodarussloani Gonatusantarcticus Mastigoteuthis sp. Unidentified cranchids 9 10 9 9 9 9 9 9 9 9 9 10 11 11 11 Lissodelphis peronii Squids Fishes Ommastrephidae Gonatidae Mastigoteuthidae Cranchiidae Bathylagidae Photichthyidae Myctophidae Merlucciidae Engraulididae Atherinidae Carangidae Bathylagus sp. Vinciguerria sp. Unidentified myctophids Hygophumhanseni LampallYctuscf. intricarius Lampanyctusparoicauda Macruronus novaezelandiae Engraulis ringens Odontesthes ragia Trachurusmurphyi 8 1,8 8 8 1 8 2,8 8 I 8 I Leatherwood and Walker, 1979; 2Woodhou&e et at., 1985; 3Scheffer and Slipp, 1948; 4Sullivan and Houck, 1979; 5Clarke, 1986; 6Norris and Prescott, 1961; 7Beach et at., 1985; BFitch and Brownell, 1968; 9Torres and Aguayo, 1979; 1OBaker, 1981; [IVan Waerebeek and Oporto, 1990. RIGHT WHALE DOLPHINS 351 'ABLE 4 Associations of right whale dolphins with other species of marine mammals Order, Family Sources Species LissodelPhis borealis Cetacea,Delphinidae Cetacea,Phocoenidae Cetacea,Ziphiidae Cetacea,Physeteridae Cetacea,Balaenopteridae Cetacea, Eschrichtiidae Pinnipedia, Otariidae Lissodelphisperonii Cetacea,Delphinidae Lagenorhynchus obliquidens DelPhinus delphis Tursiops truncatus Grampus griseus GlobicePhala sr. Phocoenoides dalli Berardius bairdii Mesoplodon sr. Physeter macrocephalus Megaptera novaeangliae Balaenoptera borealis Balaenoptera physalus Eschrichtius robustus Zalophus califomianus GlobicePhala sp. Lagenorhynchus crnciger Lagenorhynchus obscurns Delphinus delphis Tursiops trnncatus Cetacea, Balaenopteridae I Klumov, Balaenoptera physalus 1,2,3,4,5,6,7,8,9,10,11 4, 12 6 3,5,6,7,8,11 2, 3, 6, 8, 10 2,4,7,8 6 8 8 6,8,13 6, 13 6 4 4 14,15, 18, 19, : 14,21, : 23,24 21 IR 17, 18, 1 J, 20, 21 1959; 2Norris and Prescott, 1961; 3Fiscus and Niggol, 1965; 4Leatherwood, 1974; 5Wahl, 1977; 6Leatherwood and Walker, 1979; 7Braham, 1983; 8Dohl et at., 1983; 9Kasuya and Jones, 1984; loBaird and Stacey, 1991; II Black and Jelrerson, 1992; 12Smith et at., 1986; 13Brownell, 1964; 14Cruickshank and Brown, 1981; 15Laws and Nieuwenhujis, 1981; 16Bastida and Bastida, 1984; 17Enticott, 1986; 18Miyazaki and Kato, 1988; 19Kasamatsu et at., 1988; 2oKasamatsu et at., 1989; 21Rose and Payne, 1991; 22Fraser, 1955; 23J. S. Grove, in tilt. 12June 1990; 24Yan Waerebeek and Guerra, 1987. an interesting behaviour pattern in southern right whale dolphins off southern Africa. In a loose herd, one animal began leaping out of the water, circling the entire school. Then the entire school exploded outwards, with animals swimming directly away from the centre in all directions. This was observed on two consecutive days, but has not been reported elsewhere. The behaviour of right whale dolphins relative to ships is highly variable; they may approach them and ride the bow wave or may actively avoid them (Leatherwood and Walker, 1979; Cruickshank and Brown, 1981; Rose and Payne, 1991). Apparently, at least for the northern species, bow-riding occurs more often in the company of other species (Leatherwood et at., 1987). Northern right whale dolphins have reportedly been observed "standing by" injured school mates (Cassin, 1858), but Caldwell and Caldwell (1966) considered the identification of species here questionable. Little else is known of their social behaviour. 352 T. A. JEFFERSON ET AL. FIG. 6 Low angle leapsof northern (top) and southern (bottom) right whale dolphins. The bottom photo also shows an entirely black southern right whale dolphin and an associationwith the common dolphin (DelphinusdeIPhis).(Photos by M. W. Newcomer (top) andJ.S. Grove/Eye on the World Photography (bottom).) RIGHT WHALE DOLPHINS 353 FIG. 7 Northern right whale dolphin performing side slaps. (Photo by T. A. Jefferson.) Soundproduction Sounds of northern right whale dolphins have been reported by Fish and Turl (1976) and Leatherwood and Walker (1979). Most commonly heard were clicks with high repetition rates. There were few whistles, especially compared with other oceanic dolphins. The sounds of southern right whale dolphins have not been described. Parasites and Disease Woodhouse et at. (1985) and Cowan et at. (1986) provided the only detailed information on pathology of northern right whale dolphins, bas'ed on eight and six stranded specimens, respectively. They reported heart scars, lung abcesses and inflammation, pulmonary oedema, ulceration, and brain lesions in some specimens. Published parasite records for both species are reviewed in Table 5. Effects of most parasites are largely unknown, but the trematode fluke Nasitrema sp. can cause major damage to the air sinuses, inner ears, and brain, and has been T. A. JEFFERSONET AL. 354 TABLE 5 Parasites of right whale dolphins Location Species Sources Lissodelphis borealis Brain Air sinus/ears Stomach Blubber Muscle Peritoneum External LiI'sodelphil'peronii Air sinuses Lungs Stomach Colon Intestine Liver Blubber Nasitrema sr. Crassicaudasr. Nasitrema sr. Nasitrema globicePhalae Anisakis cr. simPlex Penellasr. 1,2,3 1,3 1,3,4: 1,5 1,3 1,6,7 8 3 1 1 1,9 Nasitrema sp. Stenurussp. Anisakis simPlex Unidentified trematode StrobilocePhalustriangularis Tetrabothriumforsteri OrthosPlanchusantarcticus Delphinicola tenuis Phyllobothrium sp. Phyllobothrium delphini 10, 11 10 10, 12, 13 10 13 13 12 13 12 10 Phyllobothrium sr. Phyllobothrium delphini Sarcosporidiasr. Monorygmagrimaldii Xenobalanussr. 1Dailey and Walker; 1978; 2Dailey, 1985; 3Cowan et aZ., 1986; 4Walker, 1975; 5Neiland et aZ., 1970; 6Dailey and Brownell, 1972; 7Woodhouseet aZ.,1985;8Testa and Dailey, 1977;9Leatherwoodand Walker, 1979; IOVan Waerebeek and Oporto, 1990; llReyes and Brito, 1990; 12Baker,1981; 13Fernandez,1987. implicated as a factor in the stranding and death of someanimals (Ridgway and Dailey, 1972;Walker, 1975). Live Maintenance Due to the difficulty of capturing and maintaining these open-ocean species, there have been few attempts to live capture right whale dolphins (Mitchell, 1975). One northern right whale dolphin survived in captivity for 15 months (Walker, 1975), but all other captives lived less than 3 weeks (Wood, 1973; Walker, 1975; Reeves and Leatherwood, 1.984). There have been no reported attempts to live capture southern right whale dolphins (International Whaling Commission, 1984). RIGHT WHALE DOLPHINS 355 Human Effects Directed fisherie! Northern right whale dolphins were occasionally taken by nineteenth century whalers (Mitchell, 1975). In the western Pacific, coastal fisheries off Japan have taken them for many years, with 465 reported killed in the harpoon fishery in 1949 (Wilke et at., 1953). Although this fishery mainly targets other small cetaceans, northern right whale dolphins continue to be taken (Miyazaki, 1983). Southern right whale dolphins were also taken occasionally by whalers in the last century, primarily for their meat (Mitchell, 1975; Cruickshank and Brown, 1981; Goodall and Galeazzi, 1985). They are reportedly infrequently caught off the coasts of Peru and Chile, where they are used as food or crab bait (Aguayo, 1975; Torres and Aguayo, 1979; Goodall and Cameron, 1980; Van Waerebeek and Reyes, 1990). By-catches A few incidental catches of northern right whale dolphins occur in purse-seine operations in japan and the Soviet Union (Klumov, 1959; Ohsumi, 1972), and small numbers have been killed in commercial and experimental salmon driftnet operations in the western and central Pacific (International North Pacific Fisheries Commission, 1981, 1982; International Whaling Commission, 1989). The North Pacific squid driftnet fleets of japan, Taiwan, and South Korea are known to take northern right whale dolphins (International North Pacific Fisheries Commission, 1990). Total numbers killed in the late 1980s were estimated at about 15000-24000 per year, and this mortality is considered to have depleted the population to 24-73% of its pre-exploitation size (Mangel, 1993). Northern right whale dolphins have also been observed entangled in net debris in the western Pacific (Gooder, 1989). The total reported take of northern right whale dolphins by japan in 1987 was 261 individuals, but this is likely an underestimate of the true numbers taken (International Whaling Commission, 1989). Although there have been no directed fisheries for northern right whale dolphins in the eastern Pacific, they have been killed incidentally in other activities. Norris and Prescott (1961) and Beach et at. (1985) reported beachstranded specimens that had been shot. Small numbers have been reported taken in American drift nets set for sharks and swordfish off southern California (Diamond et ai., 1987), and Oregon and Washington (Stick and Hreha, 1989). A short-lived Canadian experimental driftnet fishery for flying squid killed a total of 13 in 1986 and 1987 (Baird and Stacey, 1991). 356 T. A. JEFFERSON ET AL Since 1989, there has been evidence of a significant incidental catch of southern right whale dolphins in the rapidly developing swordfish gillnet fishery off northern Chile (see Van Waerebeek et at., 1991). Pollution The effects of habitat degradation and pollution on right whale dolphins are unknown, but as Baird and Stacey (1991) pointed out for the northern species, their pelagic habitat is probably safer from human effects than coastal areas are. We know of no published accounts of pollutant levels in right whale dolphins; however, high concentrations of environmental contaminants have been found in other pelagic small cetaceans (O'Shea et al., 1980). The seasonal shoreward movements of right whale dolphins may put them at increased risk during certain times of the year. Acknowledgments The authors thank R. W. Baird, A. 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