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Van Waerebeek , K. , Goodall , R. N. P. , and Best , P. G. ( 1997 ). A note on evidence for pelagic warm-water dolphins resembling Lagenorhynchus . Rep. Int. Whal. Commn 47 , 1015 – 1017 .

White , R. W. , Reid , J. B. , Black , A. D. , and Gillon , K. W. ( 1999 ). “ Seabird and Marine Mammal Dispersion in the Waters Around the Falkland Islands 1998–1999 . ” Joint Nature Conservation Committee , UK .

Humpback Dolphins S. chinensis and S. teuszii

GUIDO J. PARRA AND GRAHAM J.B. ROSS

I. Characteristics and Taxonomy

Humpback dolphins Fig. 1 are medium-sized delphinids found in coastal waters of the eastern Atlantic (West Africa), Indian, and West Pacifi c Oceans ( Fig. 2 ). Genetic and morphologi-

cal information indicate that they are delphinids (family Delphinidae). Initially, humpback dolphins were thought to be related to Sotaliaspp., small delphinids that inhabit coastal and riverine waters of South America and Steno bredanensis , an oceanic dolphin species. However, molecular studies indicate that humpback dolphins are more closely related to tropical oceanic species, including those of the genera Stenella , Delphinus , Tursiops , and Lagenodelphis ( LeDuc et al. , 1999 ). The taxonomy of the genus Sousa is not well established and no study to date has resolved the number of species in the genus. Current views range from recognition of only a single, variable species – S. chinensis – to three nominal species: S. chinensis (Pacifi c Ocean), S. plumbea(Indian Ocean), and S. teuszii (Atlantic Ocean). Other nominal spe-cies include S. lentiginosa ( Owen, 1866 ) and S. borneensis ( Lydekker, 1901 ). Studies on skull morphology support the division of the genus into the chinensis , plumbea , and teuszii forms ; however, patterns of cranial variation were thought conservative and no taxonomic revisions were recommended ( Jefferson, 2004 ). Recent phylogenetic studies indicate that Australian humpback dolphins are highly divergent from those in Southeast Asia and may represent a distinct species ( Fr è re et al ., in press ). Further morphological and molecular studies are needed to resolve the taxonomy of this highly variable genus. At present, the Scientifi c Committee of the International Whaling Commission recognizes only two species, S. teuszii and S. chinensis , the latter comprising all Indo-Pacifi c populations of Sousa .

Humpback dolphins are characterized by a robust and medium-sized body ( Jefferson and Karczmarski, 2001 ; Ross et al ., 1994 ). The melon is moderate in size, slightly depressed and in profi le slopes gradually to an indistinct junction with the long, narrow ros-trum. Neonates have vibrissae. The gape is straight. The broad fl ip-pers are rounded at the tip and the fl ukes are broad and full, with a deep median caudal notch. Dorsal and ventral ridges on the caudal peduncle are well developed in African and Indian Ocean popula-tions. Overall, humpback dolphins reach a maximum total length of 2.6 – 2.8 m in different parts of their distribution. A few animals exceeding 3.0 m in length have been recorded in the Arabian and Indian regions. Maximum weights of 250 – 280 kg have been recorded for humpback dolphins in South Africa and Hong Kong, respectively. Sexual dimorphism in total body length and weight is only appar-ent in the South African animals where mean lengths and weights

for fully grown males are 2.70 m and 260 kg compared to 2.40 m and 170 kg in females.

Characteristic features of the skull include a long, narrow rostrum strengthened by raised premaxillary bones and increasingly com-pressed toward the tip, large temporal fossae on which the jaw mus-cles insert and pterygoid bones that are separated in the midline by up to 11 mm. A broad gap exists between the posterior margin of the maxillary bones and the supraoccipital crest of the skull. The man-dibular symphysis is long with each jaw bearing 27 – 39 teeth, wedge shaped at their base. Skull morphology is similar in all populations, apart from lower tooth counts, a shorter mandibular symphysis and a broader cranium in West African animals ( S. teuszii ). For a thor-ough review of geographic variation in skull morphology of hump-back dolphins, see Jefferson and Van Waerebeek et al . (2004).The mean number of teeth per jaw increases eastward from 28 or 29 in West African animals ( teuszii form) to 35 or 37 teeth in north Indian Ocean populations ( plumbea form) and 33 or 35 teeth in Southeast Asian and Australian animals ( chinensis form). The range of verte-bral formulae in South African animals was 7 C, 11 – 12 T, 9 – 12 L, 20 – 24 Ca � 49 – 52. The fi rst and second cervical vertebrae are fused. Vertebral counts in humpback dolphins farther east are simi-lar to those of the South African sample (49 – 53), while West African humpback dolphins have 52 – 53 vertebrae.

Regional differences occur in external morphology, especially in coloration and shape and size of dorsal fi n and hump ( Fig. 1 ). In Indian humpback dolphins ( plumbea form), the dorsal fi n is smaller, slightly falcate, less triangular in shape and sits atop a prominent and well-developed dorsal hump ( Fig. 1A ). The dorsal fi n of Pacifi c humpback dolphins ( chinensis form) is short, triangular in shape, slightly recurved and has a wide base without a basal hump ( Fig. 1B ).Atlantic humpback dolphins ( S. teuszii ) have a very similar dorsal fi n shape and basal hump to Indian humpback dolphins, but the hump tends to be more pronounced and fi n more triangular in shape with a rounded tip. Coloration varies greatly according to geographic location and age. Calves throughout the range are mostly dark gray above with a lighter ventral surface. Adults from the western Indian Ocean are usually dark gray; with lighter ventral surface shading to off-white with light spotting sometimes present ( Fig. 1A ). Atlantic humpback dolphins have a similar appearance to that of Western Indian Ocean animals. Adults from Australia are pale gray in color with fl anks shading to off-white and spotted toward the ventral sur-face ( Fig. 1B ). Rostrum, melon, and dorsal fi n in Australian animals whiten with age. Most adults from Southern China are pure white, often with dark spots on the body and a pinkish tinge resulting from blood fl ushing during periods of high activity ( Fig. 1C ).

II. Distribution and Abundance Humpback dolphins are tropical to subtropical species found

mainly in coastal waters of the eastern Atlantic, Indian and western Pacifi c Oceans ( Fig. 2 ). Atlantic humpback dolphins are endemic to coastal waters of the eastern Atlantic of West Africa from Morocco to Southern Angola ( Van Waerebeek et al ., 2004 ). Indo-Pacifi c hump-back dolphins (including the plumbea and chinensis forms) occur from South Africa to Central China and northern Australia ( Jeffersonand Karczmarski, 2001 ). Recent observations suggest that the plumbea form ranges from False Bay in South Africa to at least the Bay of Bengal in India. The chinensis form extends from the Gulf of Thailand east to central China and northern Australia. The distri-butions of the plumbea and chinensis forms may overlap in the Bay of Bengal. At least one humpback dolphin, most likely S. plumbea ,

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reached the Mediterranean Sea via the Suez Canal ( Kerem et al ., 2001 ). Australian humpback dolphins range from approximately the Queensland – New South Wales border (31°27 S, 152°55 E) to west-ern Shark Bay, Western Australia (25° 51 S, E113° 20 E).

Estimates of population size are only available for a few selected areas. At least on a local scale, populations of humpback dolphins are small (usually in the low hundreds) with the exception of the Hong Kong/Pearl River estuary population in China which is estimated to be at about 1500 animals ( Jefferson, 2000 ). In contrast, preliminary sur-veys of the Xiamen Area to the north of Hong Kong indicate a small population of 80 humpback dolphins ( Jefferson and Hung, 2004 ). Population estimates in Australian waters suggest that there are about 100 individuals inhabiting Moreton Bay, southern Queensland and less than 100 animals in Cleveland Bay, northeast Queensland ( Corkeron et al ., 1997 ; Parra et al. , 2006a ). Populations of South Africa were esti-mated at 466 (95% CI � 447 – 485) dolphins in Algoa Bay ( Karczmarski et al ., 1999b ) and 74 (95% CI � 60 – 88) in Richards Bay ( Keith et al ., 2002 ). In Maputo Bay, Mozambique, preliminary estimates indicate that about 105 (95% CI � 30.5 – 150.9) humpback dolphins inhabit this area ( Guissamulo and Cockcroft, 2004 ). Between 58 and 65 humpback

Figure 1 Regional differences in the external appearance of humpback dolphins. (A) Humpback dolphin from the east coast of South Africaexhibiting dark gray coloration and well-developed dorsal hump typical of animals from the Eastern Atlantic ( S. teuszii ) and Western Indian Ocean ( Sousa plumbea ). (B) Humpback dolphin from Cleveland Bay, Australia showing lighter coloration and absence of dorsal hump dis-tinctive of animals from the Eastern Indian Ocean and Pacifi c Ocean ( Sousa chinensis ). (C) External appearance of adult humpback dolphin from Hong Kong showing the brilliant white/pink coloration characteristic of animals in southern China which differs from conspecifi cs else-where. (D) Humpback dolphin from the Bay of Bengal, India. Note the absence of dorsal hump and resemblance to animals from the Pacifi c Ocean ( S. chinensis ).

(A)(B)

(C) (D)

0°

60°

30°

Indian ocean

Atlantic ocean

Pacific ocean

0°

30°

60°

30° 60° 90° 120° 150°

S.teuszii S. plumbeaS. chinensis

Figure 2 Map showing the distribution of humpback dolphins in the Eastern Atlantic, Indian and west Pacifi c Oceans.

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dolphins occur in a small area (26 km 2 ) off the south coast of Zanzibar ( Stensland et al. , 2006 ). A very small population ( � 100 individuals) has been identifi ed off central western Taiwan ( Wang et al ., 2004 ).

III. Ecology Though key habitats vary with geographical location, humpback

dolphins are typically found in shallow waters of less than 20 m, close to the coast and associated with river mouths, mangroves, tidal chan-nels and inshore reefs ( Karczmarski et al ., 2000a ; Atkins et al ., 2004 ; Parra, 2006 ). In Australia, humpback dolphins occur occasionally off-shore but generally in shallow water around islands or reefs as well as in reef lagoons such as Ningaloo Reef, Western Australia ( Parra et al. , 2004 ). In Australia, China and India, high-density areas are usually associated with estuarine habitats and deep water channels. In China, dolphins may swim up rivers for tens of kilometers. In the Arabian region, humpback dolphins are mainly found in shallow coastal waters along low-energy sandy shorelines, though in some areas around Oman humpback dolphins are frequently seen along high-energy rocky shorelines in waters over 40 m deep ( Baldwin et al ., 2004 ).

Limited quantitative data are available on the feeding ecology of humpback dolphins throughout their range. Based on studies in South Africa and Hong Kong ( Barros and Cockcroft, 1991 ; Barros et al. , 2004 ), it appears that humpback dolphins are opportunistic-generalist feed-ers, eating a wide variety of coastal, estuarine and reef-associated fi shes (and occasionally cephalopods and crustaceans) both on the bottom and within the water column ( Fig. 4 ). Fishes in the families Haemulidae, Sciaenidae, Sparidae, Mugilidae and Clupeidae have been identifi ed as important prey items across the South African and Chinese range of Sousa . The most common fi sh prey species eaten by South African ani-mals were Mugil cephalus , Pomadasys olivaceum , and Pachymepoton aneum and by Chinese animals, Johnius sp. Collichthys lucida and Thryssa spp. Prey species reported from Senegal include Pristipoma jubelini , Ethmalosa fi mbriata , and Mugil spp. Incidence of scars result-ing from interactions with sharks has been observed in South African and Australian animals. Adult tiger ( Galeocerdo cuvier ), great white (Carcharodon carcharias ), and bull ( Carcharinus leucas ) sharks are the most likely predators of humpback dolphins. The effects of predation on humpback dolphins ’ ecology are uncertain.

IV. Behavior and Physiology Humpback dolphins swim slowly at about 5 km/h, surfacing briefl y

at intervals of up to a minute. Longer dives may last up to 5 min. Typically they avoid boats and rarely bow-ride. Nevertheless, animals in Hong Kong appear to be used to the presence of boats and have been observed bow-riding dolphin-watching boats. When approached, humpback dolphins generally dive, split up into small groups or sin-gle animals and often change course underwater, re-appearing unex-pectedly some distance away. When a humpback dolphin surfaces, the beak or occasionally the whole head is typically raised clear of the water and the body is arched, showing the upper back and dorsal fi n while the rest of the body remains underwater. Flukes are usually exposed at the surface before animals go for a deep dive. Humpback dolphins display a wide variety of aerial displays including vertical leaps, side leaps and forward/backward somersaults ( Fig. 3 ).

The observed daytime behaviors of humpback dolphins include foraging/feeding, traveling, socializing and resting ( Parsons, 2004a ). Daytime behavior in Algoa and Richards Bays (South Africa), Hong Kong and Cleveland Bay (northeast Queensland, Australia) is domi-nated by foraging activities followed by traveling and socializing.

Foraging activities are usually associated with inshore reefs, tidal chan-nels and river mouths. In Algoa Bay, foraging behavior showed tidal, diurnal and seasonal patterns with increased feeding at high tide in the morning and evening and during the winter season. Cooperative feeding appears to be limited. Individuals in foraging schools are usually widely dispersed (50 – 100-m apart), move in various directions without an obvious pattern, dive frequently and steeply downward [often preceded by fl uke (tail fi n) up or peduncle (tail stock) arches] and have extended submersion times of more than 2 min. At the sur-face, individuals often display rapid accelerations and erratic move-ment while chasing fi sh. In northeast Queensland, Australia and in the tidal channels of the Bazaruto Archipelago, Mozambique, humpback dolphins have been observed beaching themselves intentionally as they chase fi sh into shallow waters and sandbanks. Humpback dolphins in Hong Kong are frequently seen feeding in the freshwater/saltwater mixing zone. Schools foraging behind fi shing trawlers are common in Australia and Hong Kong and for some individuals this appears to be a major source of food.

Socializing (including mating) in humpback dolphins is character-ized by individuals in close proximity showing high levels of physical interaction including body contact (animals touching and biting each other and rubbing their bodies) and frequent aerial behavior such as leaps and somersaults. Fins and fl ukes often break the surface of the water. Copulation lasting 20 – 30 sec occurs with one dolphin inverted below its partner. Observations of dolphins rising vertically belly to

Figure 3 An adult humpback dolphin doing a somersault in Cleveland Bay, Queensland, Australia.

Figure 4 Humpback dolphin catching a Mullet ( Liza spp.) at the mouth of the Devi River in Orissa, India.

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belly in the Arabian Gulf and the Indus delta have been ascribed to mating behavior. Mating and births occur year round. Allomaternal care of offspring has been suggested for humpback dolphins in Algoa and Plettenberg Bays, South Africa.

Throughout their range, humpback dolphins are most frequently seen in relatively small schools of less than 10 animals. Solitary animals and schools of 2 – 6 individuals are the most common, although aggre-gations of 30 – 100 individuals have been observed along the Arabian Sea coast of Oman. In general, schools consist mainly of adult animals only or combinations of adults, juveniles, and calves. Schools solely composed of juveniles are rare. Little seasonal variation in school size occurs in Australian, Hong Kong, and Mozambique waters. However, signifi cant increases in school size have been documented during sum-mer and winter in Algoa and Plettenberg Bays, South Africa. School size also appears to vary according to behavioral activity. For example, in Cleveland Bay, Australia, socializing schools of humpback dolphins are larger than schools that are foraging or traveling. Additionally, schools foraging behind trawlers are larger than schools foraging independently of trawlers or traveling. Studies in South Africa, Hong Kong, and Australia indicate that humpback dolphins live in a fi ssion – fusion society where individuals associate in schools that change often in size and composition. Long-lasting affi liations among adult animals do occur but are uncommon. Female – calf associations are stable and strong during the fi rst 3 – 4 years.

Sound production and reception are vital to humpback dolphins in the often murky habitat they occupy. The acoustic repertoire of Pacifi c humpback dolphins includes a variety of sounds similar to those of other delphinids, ranging in frequency from a minimum of 0.6 kHz to a maximum of at least 200 kHz ( Van Parijs and Corkeron, 2001c ; Goold and Jefferson, 2004 ). Sounds produced by Australian humpback dol-phins have been classifi ed into fi ve different vocalization categories of variable frequency and length: broad-band clicks ( � kHz, 0.1 – 10 sec); barks (0.6 – 22 kHz, 0.1 – 7.4 sec); quacks (0.6 – 3.7 kHz, 0.08 – 2.7 sec); and grunts (0.09 – 1.4 kHz, 0.06 – 2 sec) ( Van Parijs and Corkeron, 2001b, c ). High-frequency broadband clicks appear to be used for echolocation and have been recorded mostly during foraging activities and to a lesser extent during socializing and traveling. Barks and quacks are produced predominantly during social and foraging behaviors, while grunts appear to be restricted to social behavior. Additionally, 17 dif-ferent narrow-band frequency-modulated sounds (whistles) have been described for Australian humpback dolphins. These whistles are mainly heard during social behavior. It has been suggested that humpback dolphins may use their hearing capabilities to locate sound-producing prey by passively listening for the sounds that they make.

Throughout a signifi cant part of their range, humpback dolphins share their coastal habitat with Indo-Pacifi c bottlenose dolphins (Tursiops aduncus ), snubfi n dolphins ( Orcaella heinsohni ) and fi nless porpoises ( Neophocaena phocaenoides ). Interactions with bottlenose and snubfi n dolphins have been recorded in the wild. Mixed schools of humpback and bottlenose dolphins have been observed in South Africa ( Karczmarski et al ., 1997 ), Tanzania ( Stensland et al ., 2003 ), Oman ( Baldwin et al. , 2004 ) and Australia ( Corkeron, 1990 ). In South Africa, most interactions appear to be non-agonistic, with humpback dolphins remaining in the periphery or at distance of the school of bottlenose dol-phins. However, aggressive interactions from bottlenose dolphins toward lone humpback dolphins have been documented in South Africa and Oman. In Tanzania, dolphins in mixed schools are often seen resting, traveling, and socializing, including male bottlenose dolphins herding female humpback dolphins. Mixed schools of bottlenose and humpback dolphins in Moreton Bay, Australia, have only been seen while feeding behind trawlers. During these interactions, bottlenose dolphins were

higher in number and appeared to be dominant over humpback dol-phins. Interactions between humpback and snubfi n dolphins have only been observed in northeast Queensland, Australia ( Parra, 2006 ). Here, interspecifi c interactions are mainly of aggressive-sexual nature with humpback dolphins dominating snubfi n dolphins. No interactions have been observed between fi nless porpoises and humpback dolphins. In Hong Kong these species show spatial and temporal differences in their habitat use. Interspecifi c interactions between humpback dolphins and other dolphins and porpoises within their range appear to be complex and may be the result of anti-predator and foraging strategies, interspe-cifi c mating or competition for resources.

Although humpback dolphins do not undergo large-scale sea-sonal migrations, seasonal changes in their distribution and abun-dance have been observed in South Africa ( Karczmarski et al. , 1999a ), Mozambique ( Guissamulo and Cockcroft, 2004 ) and in Hong Kong and adjacent waters ( Jefferson, 2000 ). Long-term observations of indi-vidual animals in localized areas in Australia, Hong Kong and South Africa indicate varying degrees of site fi delity, with some animals using local study areas seasonally and some others throughout the year. For example, in Cleveland Bay, northeast Queensland, Australia, most humpback dolphins are not permanent residents, but it was found that individuals did use the same areas within the bay regularly from year to year following a movement model of emigration and re-immigration ( Parra et al ., 2006a ). At Lantau Island, Hong Kong, humpback dol-phins are present year round in waters to the north but shift their dis-tribution to the south and east during the summer monsoon season ( Parsons, 1998a ). These seasonal changes in distribution and abun-dance are presumably associated with changes in prey availability and increase in the outfl ow of the Pearl River. Individual linear move-ments vary from only a few tens of kilometers in Hong Kong up to 120 km along the Natal and Eastern Cape coast in South Africa. Large linear movements seem unlikely, as extensive reviews of photo-iden-tifi cation catalogs from areas wide apart ( � 500 km) have yielded no matches. The home range size of humpback dolphins is unknown mainly because of the localized nature of the studies conducted and the diffi culties in tracking individual animals for long periods of time. Individuals in Hong Kong and the Pearl River estuary region showed range sizes from 24 to 304 km 2 , with an average of 99.5 km 2 ( Hung and Jefferson, 2004 ). In Cleveland Bay, northeast Queensland, Australia, a representative range of 190 km 2 and a core area of 17 km 2 were identi-fi ed at the population level ( Parra, 2006 ).

V. Life History Most of the information available on the life history of hump-

back dolphins comes from populations in South Africa and Hong Kong (Cockcroft/Karczmarski and Jefferson references, respec-tively). Births occur year-round, although there is evidence of sea-sonality for South Africa and China. In South Africa, calving peaks in spring or summer, the gestation period lasts 10 – 12 months, lactation may last � 2 years, sexual maturity is reached at 10 years of age for females and 12 – 13 years for males and a 3-year calving interval has been suggested. In Hong Kong, most births occur between January and August, a gestation period of 11 months is presumed, length at birth is assumed to be about 100 cm and females reach sexual matu-rity at 9 – 10 years of age.

VI. Interactions with Humans The conservation status of almost all populations of humpback

dolphins throughout their range is uncertain, primarily because monitoring of population sizes and mortality is lacking in most

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regions. Humpback dolphins are currently listed as Near-Threatened (S. chinensis) and Vulnerable (S. teuzsii) by the IUCN and are listed in CITES Appendix I the western Taiwan population of S. chinensisis listed as Critically Endangered. Population estimates for a few selected areas indicate that the populations are relatively small (with the exception of Hong Kong) and thus vulnerable to anthropogenic mortality and potentially rapid population declines. Humpback dol-phins are vulnerable to human impact because of their dependence on coastal and estuarine habitats which are under increasing pressure from expanding human populations. Anthropogenic threats through-out their range include wildlife tourism, direct takes, incidental cap-tures in gill nets and shark nets and habitat degradation and loss.

In Australia, observations and interactions with free-ranging humpback dolphins occur only in Queensland ( Parra et al ., 2004 ). In southern Queensland, up to seven free-ranging humpback dol-phins visit Tin Can Bay regularly, where they are fed fi sh by visitors. Dedicated dolphin-watching trips including humpback dolphins are limited to a handful of boat operators in Moreton Bay and in Hervey Bay. In contrast, dozens of dolphin-watching operations involv-ing humpback dolphins occur in Goa ( Parsons, 1998b ), Zanzibar ( Stensland et al. , 2006 ) and in Hong Kong ( Ng and Leung, 2003 ).If properly managed, marine mammal-watching activities can ben-efi t the animals conservation through promoting increased public awareness of their biology and threats. However, dolphin watch-ing is also recognized as a potential threat to the dolphins. Careful management, offi cial dolphin-watching codes and enforcement are needed in order for the industry to be sustainable. Offi cial dolphin-watching codes have been implemented in Australia and Zanzibar, but enforcement is lacking. A voluntary code has been established in Hong Kong, while no regulations exist in India.

Incidental mortality of humpback dolphins in fi shing nets has been reported for almost all areas within their range. Though the data on levels of mortality are lacking for most regions, incidental catch in fi shing nets is thought to be one of the most direct sources of human-caused mortality of humpback dolphins. Of 28 humpback dolphins stranded in Hong Kong between May 1993 and March 1998, 21% showed signs of net entanglement and 11% of boat collision ( Parsonsand Jefferson, 2000 ). Some of the animals photo-identifi ed in Hong Kong show evidence of scars from fi sheries interactions (2.6 – 6.8%) and boat propellers (1.2 – 1.9%). Humpback dolphins are also inci-dentally caught in shark nets set for bather protection in South Africa and Australia ( Cockcroft, 1990 ; Parra et al ., 2004 ) } ( Fig. 5 ). Along the KwaZulu-Natal coast, South Africa, catches are high and shark nets represent a major threat to the small populations of humpback dolphins inhabiting these waters. A total of 129 humpback dolphins were caught in shark nets along the KwaZulu-Natal coast between 1980 and 1998 with the majority being caught at Richards Bay. Humpback dolphins were among the most commonly caught dolphin species in shark nets off Northeast Queensland, Australia. Net attendance rules and gear modifi cations have been introduced in Queensland’s inshore gillnet fi shery and most shark nets have been replaced with drumlines to reduce the incidental take of non-target species. However, enforcement is lacking in remote areas and there is no evidence that any of these measures have provided any benefi t to the conservation of humpback dolphins.

At present, directed takes of humpback dolphins are rare and are probably restricted to occasional opportunistic hunting. An estimated 22 humpback dolphins were caught intentionally for human con-sumption between 1986 and 1999 off the east coast of Madagascar ( Razafi ndrakoto et al ., 2004 ). In Zanzibar, dolphins were hunted for shark bait and for local consumption until 1996 ( Stensland et al. , 2006 ). This hunt has now been replaced by dolphin-watching tourism

which has become an alternative livelihood for the local communi-ties. A total of 36 individuals were taken in Xiamen, China in the early 1960s to determine if leather could be made from the skin ( Jefferson and Hung, 2004 ).

Very few humpback dolphins have been held in captivity. There are reports of live captures of a large number of Indo-Pacifi c hump-back dolphins from the Gulf of Thailand for the oceanarium trade. At least 13 humpback dolphins, most captured in the Tin Can Bay area, have been held in captivity in Australian oceanariums. Humpback dolphins from South Africa, Australia and Thailand have survived in captivity for periods from 3 months to over 30 years.

Because of increasing pressure from expanding human popu-lations (especially in coastal zones throughout the humpback dol-phins range), the major threat to all populations is degradation and destruction of coastal habitats. This degradation is mainly being caused by coastal zone development, overfi shing of prey, pollution and vessel traffi c. For example, high levels of pollutants – particularly mercury and organochlorine contaminants such as DDT – have been found in Hong Kong’s population of humpback dolphins ( Parsons,1998c ; Parsons, 1999 ; Parsons, 2004b ; Jefferson et al. , 2006 ).The high level of neonatal mortality (53% of strandings) observed in Hong Kong humpback dolphins may be related to organochlorine contamination. Ingestion of contaminated seabed sediments, prey species and transfer of contaminants via lactation are all part of the problem. Studies in Moreton Bay, Australia, indicated that noise from transiting vessels affects group cohesion in humpback dolphins ( Van Parijs and Corkeron, 2001a ). Moreover, humpback dolphins in Hong Kong tended to dive for longer periods of time in areas of high vessel traffi c ( Ng and Leung, 2003 ). In recognition of the numerous risks humpback dolphins face in Hong Kong waters, the Agriculture, Fisheries and Conservation Department (AFCD) of the Hong Kong Government funded several studies to examine the status of the local humpback dolphins. These studies led to the establishment in 1996 of the Sha Chau and Lung Kwu Chau Marine Park, northwest of Lantau Island, as well as the development of a conservation program in 2000 for the protection of humpback dolphins.

The cumulative effect of anthropogenic threats may result in the loss of populations of humpback dolphins already depleted, restricted to certain types of habitats and with small geographic ranges. However, the lack of baseline ecological data for most popu-lations makes determining the effects of habitat loss diffi cult. Due to their apparent small population sizes, detection of small and

Figure 5 Humpback dolphin entangled in a shark net in South Africa.

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progressive population declines is extremely diffi cult. Thus, detec-tion of population trends should not be the trigger for conserva-tion actions. Precautionary measures to maintain viable populations while minimizing the impacts of management decisions on different stakeholder groups are necessary. The much greater challenge of conserving all forms of humpback dolphins will be the maintenance of high-quality habitat throughout the highly populated develop-ing countries that coincide with their coastal distribution. Improved understanding of humpback dolphins ’ biology, ecology and taxon-omy will be a key element toward their successful conservation and management.

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Humpback Whale Megaptera novaeangliae

PHILLIP J. CLAPHAM

The humpback whale ( Fig. 1 ) is one of the best known and easily recognizable of the large whales. It is known for its frequent acrobatic behavior and its occasional tendency to

approach vessels. In the last 30 years, thousands of humpback whales have been identifi ed individually from natural markings (notably the pattern on the ventral surface of the tail fl ukes), and as a result much has been learned about the biology and behavior of this species.

I. Characteristics and Taxonomy At close range, humpback whales are easily distinguished from

any other large whale by their remarkably long fl ippers, which are approximately one-third the length of the body. The fl ippers are ventrally white and can be either white or black dorsally depending on the population and the individual; the fl ippers of North Atlantic humpbacks tend to be white, while those in the North Pacifi c are usually black ( Fig. 1 ). The body color is black dorsally, with varia-ble pigmentation on the underside (black, white, or mottled). The head and jaws have numerous knobs called tubercles, which are also diagnostic of the species. The dorsal fi n is small but highly variable in shape ranging from low (almost absent) to high and falcate. Like all rorquals, humpbacks have a series of pleats running from the tip of the lower jaw to the umbilicus. The tail is usually raised during a dive; the underside exhibits a pattern that is unique to each indi-vidual and which ranges from all white to all black. The presence of white on the ventral surface, and the prominent serration of the trail-ing edge, distinguishes humpbacks from other whales that “ fl uke ” while diving, such as right, bowhead, blue, gray, and sperm whales.

Adult female humpback whales are typically 1–1.5 m longer than males. Maximum reliably recorded adult lengths are in the 16–17 m range, although 14–15 m is more typical ( Clapham and Mead, 1999 ).Calves are 3.96–4.57 m at birth, and approximately 8–10 m at inde-pendence ( Clapham et al. , 1999 ), which occurs at the end of the calf’s natal year. There are no easily observable differences between male and female humpbacks. Females possess a grapefruit-sized lobe at the rear of the genital slit; this lobe is absent in males ( Glockner-Ferrari and Ferrari, 1990 ). In addition, the spacing between the gen-ital slit and the anus is considerably greater in males.

The skull of the humpback whale is easily distinguished from that of other baleen whales by the narrowness of the rostrum relative to the zygomatic width. The humpback has between 270 and 400 baleen plates on each side of the mouth. The plates are usually black, although those close to the tip of the jaw are sometimes white or partly white.

The genus Megaptera is monotypic and is one of two genera in the family Balaenopteridae (the “ rorquals ” ). No subspecies are recognized. The binomial Megaptera novaeangliae derives from the Greek for “ big wing ” ( mega � pteron ) and the Latin for “ New England ” which was the origin of the specimen used by Borowski in his description of the species in 1781.

II. Distribution and Abundance Humpback whales are found in all oceans of the world. They are

a highly migratory species, spending spring through fall on feeding

Humpback Whale