Dusky dolphin
Dusky dolphin | |
---|---|
Size compared to an average human | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Artiodactyla |
Infraorder: | Cetacea |
Family: | Delphinidae |
Genus: | Lagenorhynchus |
Species: | L. obscurus
|
Binomial name | |
Lagenorhynchus obscurus (J. E. Gray, 1828)
| |
Subspecies | |
| |
Dusky dolphin range |
The dusky dolphin (Lagenorhynchus obscurus) is a
Taxonomy
It is commonly thought that the dusky dolphin was first described by John Edward Gray in 1828 from stuffed skin and a single skull shipped from the Cape of Good Hope to the British Museum. Gray first described the species as Delphinus obscurus, with the subgenus Grampus in his 1828 Specilegia Zoologica. Gray reported that the animal was captured around the Cape of Good Hope by a Captain Haviside (often misspelt "Heaviside") and sent to the British Museum though the Royal College of Surgeons in 1827.[3]
However, Gray later wrote that a similar dolphin was described as Delphinus supercilious by French surgeons and naturalists
Genetics
The dusky dolphin and the
Dusky dolphins from Argentina and southwest Africa separated 2000 generations ago from an ancestral Atlantic population and subsequently diverged without much
Description
The dusky dolphin is small to medium in length compared with other species in the family. There is significant variation in size among the different population areas. The largest dusky dolphins have been encountered off the coast of Peru, where they are up to 210 cm (6 feet) in length and 100 kg (210 pounds) in mass. The size for dusky dolphins in New Zealand have been recorded to be a length range of 167–178 cm and a weight range of 69–78 kg for females and a length range of 165–175 cm and a weight range of 70–85 kg for males.[17]
Almost no sexual dimorphism occurs in this species, although males have more curved dorsal fins with broader bases and greater surface areas.[17] The back of the dolphin is dark grey or black, and the dorsal fin is distinctively two-toned; the leading edge matches the back in colour, but the trailing edge is a much lighter greyish white. The dusky dolphin has a long, light-grey patch on its fore side leading to a short, dark-grey beak. The throat and belly are white,[18] and the beak and lower jaw are dark grey. Two blazes of white colour run back on the body from the dorsal fin to the tail. Right between the white areas remains a characteristic thorn-shaped patch of dark colour, by which the species can easily be recognised. Aside from that, dusky dolphins may be confused with other members of their genus when observed at sea. It can be distinguished from the common dolphin, which has a more prominent and longer beak and yellow flank markings.[19] The skull of a dusky dolphin has a longer and narrower rostrum than that of an hourglass dolphin or Peale's dolphin of similar age and size.[20]
Populations and distribution
The dusky dolphin has a discontinuous semi-
Dusky dolphins are found throughout New Zealand waters. The dolphin population in this area centres around East Cape and Cape Palliser on the North Island to Timaru and Oamaru on the South Island.[22] They are especially common in the cold waters of the Southland and Canterbury currents.[22] In Africa, the dusky dolphin ranges from Lobito Bay, Angola in the north to False Bay, South Africa in the south.[7] Within Australian waters, dusky dolphins have been recorded in colder waters of Kangaroo Island, eastern Tasmania, and Bass Strait,[19] although they are uncommon and those that are sighted there are possibly transients from New Zealand.[23] They are also found around Campbell, Auckland, and Chatham in the western South Pacific, Tristan da Cunha in the South Atlantic and Île Amsterdam, and Île Saint-Paul in the southern Indian Ocean.[24]
Ecology and behaviour
Dusky dolphins prefer cool, upwelling waters, as well as cold currents. They largely live in inshore waters and can be found up to the outer continental shelf and in similar zones in offshore islands.
Vocalisations and echolocation
In general, three different types of sounds are produced by dolphins (and other
Foraging and predation
Dusky dolphins prey on a variety of fish and squid species. Common fish species eaten include
When hunting in shallower waters in New Zealand and Argentina, dusky dolphins tend to forage during the day. The dolphins chase schools of fish or squid and herd them into stationary balls.
Social behaviour and reproduction
Dusky dolphins live in a
In the mating groups, the males pursue a female in high-speed chases. Females seem to prefer males with great speed and agility rather than size, strength, or aggression.[36]: 164 : 175 Females may extend the chase as long as possible so only the best male remains.[37] Females may try to evade males that are not vigorous or lack social skill.[36]: 170 Males also may form alliances to catch females.[36]: 167–69 Unlike male bottlenose dolphins, male dusky dolphins cannot monopolise females.[36]: 166 The time when female dusky dolphins first reproduce varies between regions. New Zealand dolphins first reproduce at about seven to years, with possibly six to seven years for Argentine dolphins. A study of dusky dolphins off the coast of Peru showed the reproductive cycle lasts around 28.6 months, with mother dolphins pregnant for 12.9 months, lactating for a further 12 months, and resting for 3.7 months before the cycle begins again.[3] During copulation, females tend to be on the top.[36]: 170 As with all species where females mate with multiple partners, male dusky dolphins have large testes for sperm competition.[36]: 166 Dusky dolphins sometimes engage in sexual behaviour for reasons other than reproduction, perhaps for greeting, communication, or strengthening social bonds. Homosexual behaviour between males has been observed.[34] Dolphins having sex for social reasons tend to be more relaxed.[36]: 175
Females with calves tend to gather in nursery groups in shallow water. Nursery groups likely provide mothers and calves more time to rest, which is important for both. While the behaviours of nursery groups vary by month, resting is the predominant behaviour during most months.[38]: 188 The formation of nursery groups in shallow waters also allows members to hunt prey species that inhabit in these waters. Both adults and calves have been observed to chase and catch fish, and the adults may be teaching the calves how to hunt.[38]: 188–89 In contrast to shallower waters, hunting in deep water at night may be too dangerous for calves.[38]: 189 Calves are particularly vulnerable to predators like killer whales and use of shallow water by nursery groups may be a way to avoid predation.[38]: 183 Nursery groups tend to avoid mating groups.[36]: 174 Adult males in these groups will aggressively herd and chase females. They can separate calves from their mothers and harass them, as well.[38]: 185 Calves may also become even more vulnerable to predators as they become exhausted and disoriented.[38]: 185 Mother dolphins may look after calves that are not their own.[38]: 192
Aerial behaviour
Dusky dolphins perform a number of aerial displays, including leaps, backslaps, headslaps, tailslaps, spins, and noseouts.[25] They also perform head-over-tail leaps which have been called the most "acrobatic" of the displays.[25] A headfirst re-entry is performed when a dolphin leaps entirely out of the water and positions its back in a curve while it flips the tail to land back in the water head-first. "Humping" is similar, except the snout and tail remain in the water when the dolphin is the arch.[25] Leaps, head-over-tail leaps, backslaps, headslaps, tailslaps, and spins are often done over and over again.[25] Young dusky dolphins apparently are not born with the ability to perform the leaps and must learn to master each one.[38]: 190 Calves appear to learn the leaps in this order: noisy leaps, head first re-entries, coordinated leaps, and acrobatic leaps.[38]: 190–91 Adults may perform different leaps in different contexts, and calves may independently learn how to perform leaps, as well as learn when to perform these when interacting others.[38]: 191
Relationship with humans
Status
The dusky dolphin, protected in much of its range, is listed as
The dusky dolphin is listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (
Mussel farming
The effect of
Tourism
Dusky dolphins are popular attractions for whale-watching tours. Since 1997, dolphin-watching activities have increased in Patagonia, with dusky dolphins (along with Commerson's dolphins) as the target species.[42] Tourists interested in seeing dusky dolphins grew from 1,393 in 1997 to 1,840 in 2000. Encounters with dolphins increased from 25% during 1999 to 90% in 2001.[42] Dolphin watching in this areas started as an alternative to whale watching, which was mostly based on that of the southern right whale.[42] Dusky dolphin watching is also popular in New Zealand, whose dolphin-watching industry begin in the late 1980s, as a side attraction to sperm whale watching. Whale and dolphin watching tours have grown with around 75 permitted dolphin tour operators.[43]: 235 New Zealand has several locations to view and swim with dusky dolphins, notably in Kaikōura and Marlborough Sounds.[43]: 236
While dusky dolphin tourism is a larger industry in New Zealand than it is in Argentina, the effects of tourism on the dolphins seem to be lower in the former than the latter.[43]: 241 New Zealand tours are operated under permits, and are limited in number and have conditions and guidelines related to approach procedures and swim operations.[43]: 241 By contrast, no direct regulation of dolphin watching is done in Argentina.[42] As such, dolphin activities are often disturbed by touring vessels.[43]: 233–35
See also
References
- ^ .
- ^ "Appendices | CITES". cites.org. Archived from the original on 5 December 2017. Retrieved 14 January 2022.
- ^ ISBN 0-12-588506-7.
- from the original on 23 September 2020. Retrieved 25 June 2019.
- ^ Flower, W. H. (1885). List of the specimens of Cetacea in the Zoological Department of the British Museum. London: British Museum. pp. 28–29.
- from the original on 30 October 2019. Retrieved 22 September 2019.
- ^ ISBN 0-12-373553-X
- ^ S2CID 21935077.
- .
- PMID 16325433.
- ^ from the original on 11 November 2021. Retrieved 13 July 2021.
- .
- ^ Yazdi, Parissa (2002). "A possible hybrid between the dusky dolphin (Lagenorhynchus obscurus) and the southern right whale dolphin (Lissodelphis peronii)" (PDF). Aquatic Mammals. 28: 211–17. Archived from the original (PDF) on 9 December 2022. Retrieved 3 February 2011.
- ^ Perrin, W. (2013). Lagenorhynchus obscurus. In: Perrin, W.F. (2013) World Cetacea Database. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=231434 Archived 12 March 2014 at the Wayback Machine on 2014-03-10
- ^ "List of Marine Mammal Species and Subspecies|June 2021". Society for Marine Mammalogy. Archived from the original on 27 November 2020. Retrieved 14 July 2021.
- ^ "List of Proposed, Un-named Marine Mammal Species and Subspecies|June 2021". Society for Marine Mammalogy. Archived from the original on 14 December 2023. Retrieved 14 July 2021.
- ^ a b c Cipriano, F. W. (1992). Behavior and occurrence patterns, feeding ecology, and life history of dusky dolphins (Lagenorhynchus obscurus) off Kaikoura, New Zealand (Phd. Thesis). University of Arizona.
- ^ Webber, M.C. 1987. "A comparison of dusky and Pacific white-sided dolphins (genus . Lagenorhynchus): morphology and distribution". M.S. Thesis, San Francisco State University, San Francisco CA. 102 pp.
- ^ ISBN 0-19-550870-X.
- ISBN 0-520-03283-7
- ^ Goodall, R.; de Haro, J.; Fraga, F.; Iniquez, M.; Norris, K. (1997). "Sightings and behaviour of Peale's dolphins, Lagenorhynchus australis, with notes on dusky dolphins, L. obscurus, of southernmost South America". International Whaling Commission Report. 47: 757–75. Archived from the original on 3 October 2011. Retrieved 3 February 2011.
- ^ a b c Gaskin, D E. (1972) "Whales dolphins and seals with special reference to the New Zealand region" Archived 7 July 2011 at the Wayback Machine. Heinemann Educational Books Ltd.
- .
- ^ ISBN 0-375-41141-0.
- ^ a b c d e f g h i Würsig, B.; Würsig, M. (1980). "Behavior and ecology of the dusky dolphin, Lagenorhynchus obscurus, in the South Atlantic" (PDF). Fishery Bulletin. 77: 871–90. Archived (PDF) from the original on 1 April 2011. Retrieved 3 February 2011.
- ^ Cruickshank, R.A.; Brown, S.G. (1981). "Recent observations and some historical records of southern right-whale dolphins Lissodelphis peronii". South African Fishery Bulletin. 15 (1): 109–21. Archived from the original on 4 April 2012.
- ^ Caldwell, M.C; Caldwell, D.K (1971). "Underwater pulsed sounds produced by captive spotted dolphins, Stenella plagiodon". Cetology. 1: 1–7.
- ^ a b SE Yin (1999) "Movement patterns, behaviors, and whistle sounds of dolphin groups off Kaikoura, New Zealand" Archived 25 August 2011 at the Wayback Machine, A Thesis, Texas A&M University, College Station, TX.
- ^ ISBN 0-12-373723-0
- ^ PMID 15139642.
- ^ (PDF) from the original on 27 November 2010. Retrieved 3 February 2011.
- ^ a b McFadden, C. J. (2003). "Behavioral flexibility of feeding dusky dolphins (Lagenorhynchus obscurus) in Admiralty Bay, New Zealand." MSc thesis, Texas A&M University, College Station , TX.
- ISBN 0-306-43695-7.
- ^ a b c d e Markowitz, T.M. (2004). "Social organization of the New Zealand dusky dolphin". PhD . dissertation, Texas A&M University, College Station.
- ^ Van Waerebeek, K; Reyes, JC; Alfaro, J (1993). "Helminth parasites and phoronts of dusky dolphins Lagenorhynchus obscurus (Gray, 1828) from Peru" (PDF). Aquat Mamm. 19 (3): 159–69. Archived from the original (PDF) on 4 September 2011. Retrieved 3 February 2011.
- ^ ISBN 0-12-373723-0.
- ISBN 0-226-50341-0
- ^ ISBN 0-12-373723-0.
- ^ "Appendix II Archived 11 June 2011 at the Wayback Machine" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5 March 2009.
- ^ "Convention on Migratory Species page on the Dusky dolphin". Archived from the original on 3 October 2011. Retrieved 31 August 2011.
- ^ doi:10.1002/aqc.602.
- ^ a b c d Coscarella, M. A; Dans, S. L; Crespo, E. A; Pedraza, S. N. (2003). "Potential impact of unregulated dolphin watching activities in Patagonia". J Cetacean Res Manag. 5: 77–84. Archived from the original on 8 July 2011.
- ^ ISBN 0-12-373723-0.
General
- Encyclopedia of Marine Mammals. Perrin, W. F., Wursig, B and J. G.M. Thewissen., editors. (2008) Academic Press; 2nd edition, ISBN 0-12-373553-X
- The Dusky Dolphin: Master Acrobat off Different Shores. Würsig, B., and Würsig, M., editors. (2010) Academic Press. ISBN 0-12-373723-0.
- Whales, Dolphins and. Porpoises, K. S, Norris. editor, (1977) University of California Press. ISBN 0-520-03283-7
- Sensory Abilities of Cetaceans. Thomas, J.; Kastelein, R., editors. (1990) Plenum Press. ISBN 0-306-43695-7.
- Cetacean Societies. Mann, J., editor. (2000) University of Chicago Press, ISBN 0-226-50341-0.