Australian humpback dolphin | |
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Australian humpback dolphins, Tin Can Bay, Queensland, Australia, 2016 | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Artiodactyla |
Infraorder: | Cetacea |
Family: | Delphinidae |
Genus: | Sousa |
Species: | S. sahulensis |
Binomial name | |
Sousa sahulensis | |
The Australian humpback dolphin (Sousa sahulensis) is a species of humpback dolphin and the fourth recognized humpback dolphin species chronologically. The specific name sahulensis is derived from the Sahul Shelf, located between northern Australia and southern New Guinea, where the Australian humpback dolphins occur. [3]
The species was scientifically described on 31 July 2014 in the journal Marine Mammal Science . [4] This vulnerable species' population was estimated to be 10,000 mature individuals in 2015, with numbers declining because of habitat destruction. [1]
Australian humpback dolphins are slightly different from the other three humpback dolphin species in overall length, number of teeth, vertebrae and geographic distribution. [3] The dorsal fin of the Australian humpback dolphin is lower and more wide-based than those of the Atlantic humpback dolphin and the Indian Ocean humpback dolphin, and its coloration is dark gray, while its closest humpback relative, the Chinese white dolphin, has distinctly white (often with a pink tinge) coloration. [3] The Australian humpback dolphin also has a distinctive dark dorsal feature, resembling a cape. [3]
Known size for Australian humpback dolphins range from 31/2 – 9 ft (1-2.7m). The dorsal fin is short, triangular in shape, and lacks the dorsal "hump" typical of Atlantic and Indian humpback dolphins. The body is mainly dark gray in color, with flanks shading to the light gray. A diagonal cape line extending from just above the eye and neck down to the urogenital area separates the dark back and lighter belly. White scarring and dark flecking on the head, back, dorsal fin, and tail stock are common in adult animals. Birth weight is between 88-110 lb (40–50 kg) and adult weight is between 507-550 lb (230–250 kg). [5]
Mating and calving occurs year-round. The gestation period lasts 10–12 months, lactation may last more than 2 years and a 3-year calving interval is likely. Individuals may live for at least 30 years. [5] Scientists studied the dolphins for 17 years before finally coming to the conclusion that S. sahulensis was a separate species within the Sousa genus. It was DNA that proved most useful to determining its classification. Genetic analyses found 7 unique mitochondrial DNA bases and a single nuclear DNA base supporting it status as a new species. [6]
These dolphins are known to be opportunistic, generalist feeders, eating a wide variety of coastal-estuarine and inshore reef fish. Feeding may occur in a variety of habitats (mangroves, sandy-bottom estuaries, seagrass meadows, and inshore coral reefs) and involve animals dispersed over wide areas or tight groups targeting localized prey. These marine mammals are occasionally seen chasing fish into shallows and beaching themselves to catch their prey. [5]
There is no global population estimate but subpopulation estimates are in the low hundreds. Due to their coastal distribution, Australian humpback dolphins are vulnerable to a variety of threats including incidental captures in gill nets and shark nets set for bather protection, habitat loss and degradation, vessel strikes, pollution, and climate change. [5] With an official species name, the new Aussie dolphin will have a greater chance of receiving special conservation treatment. [6]
Australian humpback dolphins have been observed strand feeding, as described for the Indian Ocean humpback dolphin. [7] They are generally shy and elusive and tend to keep their distance from boats. Humpback dolphins have been observed to display mating courtship with Australian snubfin dolphins. [5]
The Indo-Pacific humpback dolphin is a species of humpback dolphin inhabiting coastal waters of the eastern Indian and western Pacific Oceans. This species is often referred to as the Chinese white dolphin in mainland China, Macau, Hong Kong, Singapore and Taiwan as a common name. Some biologists regard the Indo-Pacific dolphin as a subspecies of the Indian Ocean humpback dolphin which ranges from East Africa to India. However, DNA testing studies have shown that the two are distinct species. A new species, the Australian humpback dolphin, was split off from S. chinensis and recognized as a distinct species in 2014. Nevertheless, there are still several unresolved issues in differentiation of the Indian Ocean-type and Indo-Pacific-type humpback dolphins.
Risso's dolphin is a dolphin, the only species of the genus Grampus. Some of the closest related species to these dolphins include: pilot whales, pygmy killer whales, melon-headed whales, and false killer whales.
The white-beaked dolphin is a marine mammal belonging to the family Delphinidae in the suborder Odontoceti.
The spectacled porpoise is a small to midsize porpoise indigenous to the Southern Ocean. It is one of the most poorly studied cetaceans, partly due to its remote range in the Southern Ocean. What little is known about this porpoise species has been gathered mainly from stranded individuals, and a few observations of living animals made at sea.
The dusky dolphin is a dolphin found in coastal waters in the Southern Hemisphere. Its specific epithet is Latin for "dark" or "dim". It is very closely genetically related to the Pacific white-sided dolphin, but current scientific consensus holds they are distinct species. The dolphin's range is patchy, with major populations around South America, southwestern Africa, New Zealand, and various oceanic islands, with some sightings around southern Australia and Tasmania. The dusky dolphin prefers cool currents and inshore waters, but can also be found offshore. It feeds on a variety of fish and squid species and has flexible hunting tactics. The dusky dolphin is known for its remarkable acrobatics, having a number of aerial behaviours. The status of the dolphin is unknown, but it has been commonly caught in gill nets.
True's beaked whale is a medium-sized whale in the genus Mesoplodon. It is native to the northern Atlantic Ocean. The common name is in reference to Frederick W. True, a curator at the United States National Museum.
The long-finned pilot whale, or pothead whale (Globicephalamelas) is a large species of oceanic dolphin. It shares the genus Globicephala with the short-finned pilot whale. Long-finned pilot whales are known as such because of their unusually long pectoral fins.
The snubfin dolphins (Orcaella) are a genus of cetaceans containing two members: the Irrawaddy dolphin and the Australian snubfin dolphin. The genus was long believed to be monotypic with the only species being the Irrawaddy dolphin; however, in 2005, supposed Irrawaddy dolphin populations inhabiting the Australian/New Guinean regions were found to be significantly different and were declared a separate new species named the Australian snubfin dolphin.
Hector's dolphin is one of four dolphin species belonging to the genus Cephalorhynchus. Hector's dolphin is the only cetacean endemic to New Zealand, and comprises two subspecies: C. h. hectori, the more numerous subspecies, also referred to as South Island Hector's dolphin; and the critically endangered Māui dolphin, found off the West Coast of the North Island.
The Indo-Pacific bottlenose dolphin is a species of bottlenose dolphin. This dolphin grows to 2.6 m (8.5 ft) long, and weighs up to 230 kg (510 lb). It lives in the waters around India, northern Australia, South China, the Red Sea, and the eastern coast of Africa. Its back is dark grey and its belly is lighter grey or nearly white with grey spots.
Humpback dolphins are members of the genus Sousa. These dolphins are characterized by the conspicuous humps and elongated dorsal fins found on the backs of adults of the species. Humpback dolphins inhabit shallow nearshore waters along coastlines across Australia, Africa, and Asia. Their preference for these habitats exposes them to various human activities such as fisheries entanglement, boat traffic, pollution, and habitat loss. Despite these risks, their nearshore presence facilitates easy observation from land.
The Atlantic humpback dolphin is a species of humpback dolphin that is found in coastal areas of West Africa.
The Indian Ocean humpback dolphin is a member of the Delphinidae family occupying coastal areas ranging from Southern Africa to Western Indochina. The Indo-Pacific humpback dolphin was formerly included within the same species, but a 2014 study revealed them to be a separate species.
The melon-headed whale, also known less commonly as the electra dolphin, little killer whale, or many-toothed blackfish, is a toothed whale of the oceanic dolphin family (Delphinidae). The common name is derived from the head shape. Melon-headed whales are widely distributed throughout deep tropical and subtropical waters worldwide, but they are rarely encountered at sea. They are found near shore mostly around oceanic islands, such as Hawaii, French Polynesia, and the Philippines.
Fraser's dolphin or the Sarawak dolphin is a cetacean in the family Delphinidae found in deep waters in the Pacific Ocean and to a lesser extent in the Indian and Atlantic Oceans.
The hourglass dolphin is a small dolphin in the family Delphinidae that inhabits offshore Antarctic and sub-Antarctic waters. It is commonly seen from ships crossing the Drake Passage but has a circumpolar distribution.
The spinner dolphin is a small dolphin found in off-shore tropical waters around the world. It is famous for its acrobatic displays in which it rotates around its longitudinal axis as it leaps through the air. It is a member of the family Delphinidae of toothed whales.
The Atlantic white-sided dolphin is a distinctively coloured dolphin found in the cool to temperate waters of the North Atlantic Ocean.
The Australian snubfin dolphin is a dolphin found off the northern coasts of Australia. It closely resembles the Irrawaddy dolphin and was not described as a separate species until 2005. The closest relative to the genus Orcaella is the killer whale, Orcinus orca. The Australian snubfin has three colors on its skin, while the Irrawaddy dolphin only has two. The skull and the fins also show minor differences between the two species.
Media related to Sousa sahulensis at Wikimedia Commons