View source for Dusky dolphin

{{Short description|Species of marine mammal}}
{{Featured article}}
{{Use New Zealand English|date=December 2024}}
{{Use dmy dates|date=May 2020}}
{{Speciesbox
| name = Dusky dolphin
| image = DuskyDolphin.jpg
| image2 = 
| image2_alt = 
| image2_caption = 
| status = LC
| status_system = IUCN3.1
| status_ref = <ref name="iucn">{{cite iucn |author=Alafaro-Shiguieto, J. |author2=Crespo, E. |author3=Elwen, S. |author4=Lundquist, D. |author5=Mangel, J. |year=2019 |errata=2020 |title=''Lagenorhynchus obscurus'' |volume=2019 |article-number=e.T11146A175604493 |doi=10.2305/IUCN.UK.2019-3.RLTS.T11146A175604493.en |access-date=17 June 2024}}</ref>
| status2 = CITES_A2 
| status2_system = CITES 
| status2_ref = <ref>{{Cite web|title=Appendices {{!}}|url=https://cites.org/eng/app/appendices.php|access-date=2022-01-14|website=cites.org|archive-date=5 December 2017|archive-url=https://web.archive.org/web/20171205014647/https://cites.org/eng/app/appendices.php|url-status=live}}</ref>
| genus = Aethalodelphis
| species = obscurus
| authority = ([[J. E. Gray]], 1828)
| subdivision_ranks = Subspecies
| subdivision = 
*''A. o. fitzroyi'' {{small|Waterhouse, 1838}}
*''A. o. obscurus'' {{small|Gray, 1868}}
*''A. o. posidonia'' {{small|Philippi, 1893}}
| range_map = Cetacea range map Dusky Dolphin.PNG
| range_map_caption = Range of the dusky dolphin
| synonyms = * ''Lagenorhynchus fitzroyi'' {{small|Waterhouse, 1838}}
* ''Delphinus fitzroyi''  {{small|Waterhouse, 1838}} 
* ''Delphinus breviceps''  {{small|Wiegmann, 1840}}
* ''Electra breviceps''  {{small|Jacquinot and Pucheran, 1853}}
* ''Lagenorhynchus breviceps''  {{small|Jacquinot and Pucheran, 1853}}
* ''Lagenorhynchus thicolea breviceps'' {{small|Jacquinot and Pucheran, 1853}}
* ''Lagenorhynchus similis'' {{small|Gray, 1868}}
* ''Clymenia similis''  {{small|Gray, 1868}}
* ''Prodelphinus petersii'' {{small|Reinhardt, 1889}}
* ''Lissodelphis panope'' {{small|Canto, 1896}}
* ''Tursio panope'' {{small|Canto, 1896}} 
| synonyms_ref = <ref>{{cite web|title=''Lagenorhynchus obscurus'' Gray 1828 (dolphin)|website=The Paleobiology Database|url=https://paleobiodb.org/classic/basicTaxonInfo?taxon_no=82067|access-date=20 March 2025}}</ref>
}}

The '''dusky dolphin''' ('''''Aethalodelphis obscurus''''') is a small [[oceanic dolphin]] found in coastal waters of the [[Southern Hemisphere]]. It is most closely related to the [[Pacific white-sided dolphin]]. The dolphin's range is patchy, major populations occurring around South America, southwestern Africa, New Zealand, and several oceanic islands, with some sightings around southern Australia. It has a somewhat stocky body with a short [[Rostrum (anatomy)|beak]] and a curved [[dorsal fin]] and flippers. Like its closest relative, the dusky dolphin has a multi-coloured pigmentation of black, grey, and white.

The species prefers cool currents and inshore waters. It lives in a [[fission–fusion society]] where groups change size based on social and environmental conditions. The dolphin feeds on several [[fish]] and [[squid]] species and has flexible hunting tactics, including [[diurnality|daytime]] [[bait ball]] herding and [[nocturnality|nightime]] feeding in [[deep scattering layer]]s. Mating is [[polygynandrous]], and several males will chase after a single female, the fittest being able to catch her and reproduce. Females raise their young in [[Crèche (zoology)|nursery groups]]. The dusky dolphin is known for its acrobatics, displaying [[Whale surfacing behaviour#Breaching, lunging, and porpoising|leaping behaviours]] which vary in complexity and may or may not create splashes. 

The dusky dolphin is classified as [[Least Concern]] by the [[IUCN Red List]] as many populations appear to be healthy and stable.  It has been [[bycatch|caught]] in [[gill nets]] and killed to be used as bait. It is a popular tourist attraction and the object of [[whale watching]] tours. Both vessels and [[mussel farm]]s can interfere with the dolphin's activities.

==Taxonomy==
The dusky dolphin was [[species description|described]] as ''Delphinus obscurus'' by [[John Edward Gray]] in 1828 based on stuffed skins with skulls shipped from the [[Cape of Good Hope]] to the [[British Museum]] in 1827.<ref name="HMM">{{cite book|editor1-last=Ridgway|editor1-first=S. H.|editor2-last=Harrison|editor2-first=R.|last1=Brownell|first1=R. L. Jr.|last2=Cipriano|first2=F.|chapter=Dusky Dolphin ''Lagenorhynchus obscurus'' (Gray, 1828) |title=Handbook of Marine Mammals: The Second Book of Dolphins and the Porpoises|volume= 6: The Second Book of Dolphins and the Porpoises |year=1998 |publisher=Elsevier|pages=85–95|chapter-url=https://books.google.com/books?id=At4jWmmaq6QC&pg=PA85 |isbn=0-12-588506-7}}</ref> Gray later wrote that a similar dolphin was described as ''Delphinus superciliosus'' by French surgeons and naturalists [[René Lesson]] and [[Prosper Garnot]] in 1826 based on a specimen near [[Tasmania]].<ref name="taxonomy">{{cite book|last1=Harlin-Cognato|first1=A. D.|chapter=Dusky Dolphins' Place in the Delphinid Family Tree|pages=1–19|editor1-last=Würsig|editor1-first=B.|editor-link1=Bernd Würsig|editor2-last=Würsig|editor2-first=M.|title=The Dusky Dolphin: Master Acrobat off Different Shores|publisher=Academic Press|year=2010|isbn=978-0-12-373723-6}}</ref>{{rp|10}} Lesson and Garnot did not keep the specimen for their description but only an illustration of it, and later taxonomists did not consider this significant enough for a new species.<ref name="HMM"/><ref name="taxonomy"/>{{rp|10–11}} Meanwhile, [[Charles Darwin]] described a "''Delphinus fitzroyi''" from a specimen harpooned off Argentina in 1838, which was later identified as this species, and thus become a [[Synonym (taxonomy)|junior synonym]].<ref name="HMM"/> The dusky dolphin was placed in the genus ''Lagenorhynchus'' by the American biologist [[Frederick W. True]] in 1889.<ref>{{cite journal|author=True, F. W.|year=1889|title=Contribution to the natural history of the cetaceans: a review of the family Delphinidae|journal=Bulletin of the United States National Museum|issue=36|pages=1–191|doi=10.5479/si.03629236.36.1|url=https://babel.hathitrust.org/cgi/imgsrv/download/pdf?id=hvd.32044066292764;orient=0;size=100;seq=7;attachment=0|hdl=2027/hvd.32044066292764|hdl-access=free|access-date=22 September 2019|archive-date=30 October 2019|archive-url=https://web.archive.org/web/20191030005702/https://babel.hathitrust.org/cgi/imgsrv/download/pdf?id=hvd.32044066292764;orient=0;size=100;seq=7;attachment=0|url-status=live}}</ref><ref name="HMM"/> ''Lagenorhynchus'' consists of the Greek {{lang|grc|lagenos}} (bottle/flask) and {{lang|grc|rhynchos}} (beak/snout); ''obscurus'' is Latin for "dark".<ref name="Vollmer 2019"/>{{rp|983, 1008}}

The genus ''[[Lagenorhynchus]]'' included the dusky dolphin, [[Pacific white-sided dolphin]], [[Atlantic white-sided dolphin]], [[white-beaked dolphin]], [[hourglass dolphin]], and [[Peale's dolphin]],<ref name="taxonomy"/>{{rp|3}} though genetic evidence indicates that this grouping is not a natural ([[monophyletic]]) taxon.<ref>{{cite journal | last1 = LeDuc | first1 = R. G. | last2 = Perrin | first2 = W. F. | last3 = Dizon | first3 = A. E. | year = 1999 | title = Phylogenetic relationships among the delphinid cetaceans based on full cytochrome b sequences | journal = Marine Mammal Science | volume = 15 | issue = 3| pages = 619–648 | doi = 10.1111/j.1748-7692.1999.tb00833.x | bibcode = 1999MMamS..15..619L }}</ref><ref>{{cite journal | last1 = May-Collado | first1 = L. | last2 = Agnarsson | first2 = I. | year = 2006 | title = Cytochrome b and Bayesian inference of whale phylogeny | journal = Molecular Phylogenetics and Evolution | volume = 38 | issue = 2| pages = 344–354 | doi=10.1016/j.ympev.2005.09.019 | pmid=16325433| bibcode = 2006MolPE..38..344M }}</ref><ref name="McGowen2020">{{cite journal|last1=McGowen|first1=M. R.|last2=Tsagkogeorga|first2=G|last3=Álvarez-Carretero|first3=S|last4=dos Reis|first4=M|last5=Struebig|first5=M|last6=Deaville|first6=R|last7=Jepson|first7=P. D.|last8=Jarman|first8=S|last9=Polanowski|first9=A|last10=Morin|first10=P. A.|last11=Rossiter|first11=S. J.|year=2020|title=Phylogenomic resolution of the cetacean tree of life using target sequence capture|journal=Systematic Biology|volume=69|issue=3|pages=479–501|doi=10.1093/sysbio/syz068|pmid=31633766 |pmc=7164366}}</ref><ref name="Galatius2025">{{cite journal|last1=Galatius|first1=A|last2=Kinze|first2=C. C.|last3=Olsen|first3=M. T.|last4=Tougaard|first4=J|last5=Gotzek|first5=D|last6=McGowen|first6=M. R.|year=2025|title=Phylogenomic, morphological and acoustic data support a revised taxonomy of the lissodelphinine dolphin subfamily|journal=Molecular Phylogenetics and Evolution|volume=205|article-number=108299|doi=10.1016/j.ympev.2025.108299|doi-access=free|pmid=39914763|bibcode=2025MolPE.20508299G}}</ref> A 2019 study proposed moving four species (the dusky dolphin, Pacific white-sided dolphin, hourglass dolphin, and Peale's dolphin) to the resurrected genus ''[[Sagmatias]]''.<ref name="Vollmer 2019">{{Cite journal|last1=Vollmer|first1=Nicole L.|last2=Ashe|first2=Erin|last3=Brownell|first3=Robert L.|last4=Cipriano|first4=Frank|last5=Mead|first5=James G.|last6=Reeves|first6=Randall R.|last7=Soldevilla|first7=Melissa S.|last8=Williams|first8=Rob|date=2019|title=Taxonomic revision of the dolphin genus ''Lagenorhynchus''|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/mms.12573|journal=Marine Mammal Science|language=en|volume=35|issue=3|pages=957–1057|doi=10.1111/mms.12573|bibcode=2019MMamS..35..957V |s2cid=92421374|issn=1748-7692|access-date=13 July 2021|archive-date=11 November 2021|archive-url=https://web.archive.org/web/20211111031311/https://onlinelibrary.wiley.com/doi/abs/10.1111/mms.12573|url-status=live|url-access=subscription}}</ref>{{rp|977}} A 2025 [[phylogenomic]] study found that ''Sagmatias'' as defined by the 2019 study is also not monophyletic and instead suggested that the dusky and Pacific white-sided dolphin be classified under a new genus, ''Aethalodelphis'', which is Greek for "sooty or dusky dolphin".<ref name="Galatius2025"/> This is considered valid by the [[Society for Marine Mammalogy]] (SMM) as of 2025.<ref name="mammalogy"/> 

The dusky dolphin is most closely related to the Pacific white-sided dolphin,<ref name= "Perrin"/> and these two [[sister species]] diverged around two million years ago. Dusky dolphin populations may have originated somewhere in the [[South Pacific]] or southern [[Indian Ocean]] and dispersed to their current range following the spread of favoured food like [[anchovies]].<ref>{{cite journal|last1=Harlin-Cognato|first1=A. D.|last2=Markowitz|first2=T|last3=Würsig|first3=B|last4=Honeycutt|first4=R. L.|year=2007|title=Multi-locus phylogeography of the dusky dolphin (''Lagenorhynchus obscurus''): passive dispersal via the west-wind drift or response to prey species and climate change|journal=BMC Evolutionary Biology|volume=7|issue=1|page=131|doi=10.1186/1471-2148-7-131|doi-access=free |pmid=17683557 |pmc=1973136 |bibcode=2007BMCEE...7..131H }}</ref> Possible hybrids of dusky dolphins with other species have been suggested based on observations and photographic evidence, including with a [[common dolphin]]<ref>{{cite journal |last1=Reyes |first1=Julio C. |title=A possible case of hybridism in wild dolphins |journal=Marine Mammal Science |volume=12 |issue=2 |pages=301–307 |year=1996 |doi=10.1111/j.1748-7692.1996.tb00581.x|bibcode=1996MMamS..12..301R }}</ref> and a [[southern right whale dolphin]].<ref>{{cite journal |first1=Parissa |last1=Yazdi |year=2002 |url=http://www.aquaticmammalsjournal.org/share/AquaticMammalsIssueArchives/2002/AquaticMammals_28-02/28-02_Yazdi.pdf |title=A possible hybrid between the dusky dolphin (''Lagenorhynchus obscurus'') and the southern right whale dolphin (''Lissodelphis peronii'') |journal=Aquatic Mammals |volume=28 |pages=211–217 |access-date=3 February 2011 |archive-date=9 December 2022 |archive-url=https://web.archive.org/web/20221209064657/https://aquaticmammalsjournal.org/share/AquaticMammalsIssueArchives/2002/AquaticMammals_28-02/28-02_Yazdi.pdf }}</ref>  

The following [[cladogram]] is based on a phylogenomic study by Galatius and colleagues (2025):<ref name="Galatius2025"/>

{{clade
|label1=[[Lissodelphininae]]
|1={{clade
|1={{clade
|1= [[Northern right whale dolphin]]
|2= [[Southern right whale dolphin]]
}}
|2={{clade
|1={{clade
|1= [[Pacific white-sided dolphin]]
|2= '''Dusky dolphin'''
}}
|2={{clade
|1={{clade sequential
|1= [[Heaviside's dolphin]]
|2= [[Peale's dolphin]]
|3= [[Hourglass dolphin]]
}}
|2={{clade sequential
|1= [[Hector's dolphin]]
|2= [[Commerson's dolphin]]
|3= [[Chilean dolphin]]
}}
}}
}}
}}
}}

===Subspecies===
Three dusky dolphin [[subspecies]] are recognised by the SMM: 

* The African dusky dolphin (''A. o. obscurus'', Gray, 1828)
* [[Robert FitzRoy|Fitzroy]]'s dolphin (''A. o. fitzroyi'', [[George Robert Waterhouse|Waterhouse]], 1838)
* The Peruvian/Chilean dusky dolphin (''A. o. posidonia'', [[Rodolfo Amando Philippi|Philippi]], 1893)<ref name="mammalogy">{{cite web|url=https://www.marinemammalscience.org/species-information/list-marine-mammal-species-subspecies/|title=List of Marine Mammal Species and Subspecies|date=13 November 2016 |publisher=[[Society for Marine Mammalogy]]|access-date=14 July 2021|archive-date=27 November 2020|archive-url=https://web.archive.org/web/20201127215426/https://marinemammalscience.org/species-information/list-marine-mammal-species-subspecies/|url-status=live}}</ref> 

A fourth subspecies, the New Zealand dusky dolphin (''L. o. superciliosus'', Rice, 1998), has been proposed but is not accepted by the SMM.<ref name="Vollmer 2019"/>{{rp|1012}}<ref name="proposed">{{cite web|url=https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/list-of-proposed-un-named-marine-mammal-species-and-subspecies/|title=List of Proposed, Un-named Marine Mammal Species and Subspecies|publisher=Society for Marine Mammalogy|access-date=14 July 2021|archive-date=14 December 2023|archive-url=https://web.archive.org/web/20231214020055/https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/list-of-proposed-un-named-marine-mammal-species-and-subspecies/|url-status=live}}</ref> Dusky dolphin subspecies are divided based on geography but also differ in skull length and tooth number.<ref name="taxonomy"/>{{rp|14}}

==Description==
[[File:Lagenorhynchus obscurus skull - Museum of New Zealand Te Papa Tongarewa - Wellington, NZ - DSC09661.jpg|thumb|right|Dusky dolphin skull at [[Te Papa]]|alt=Dolphin skull on display in museum]]
The dusky dolphin is a small [[cetacean]];<ref name="Jefferson"/> specimens from [[New Zealand]] have been recorded at {{cvt|167|–|178|cm|ft|abbr=on}} in length and {{cvt|69|–|78|kg|abbr=on}} in weight for females and {{cvt|165|–|175|cm|ft|abbr=on}} in length and {{cvt|70|–|85|kg|abbr=on}} in weight for males.<ref name="HMM"/> Peruvian dolphins may be larger, but this is based on small sample sizes;<ref name="Jefferson"/> a female was measured at {{cvt|204.5|cm|ft|abbr=on}} and a male was measured at {{cvt|206|cm|ft|abbr=on}}.<ref>{{cite journal|last=Manzanilla-Naim|first=S.|year=1989|title=The 1982–1983 El Niño event recorded in dentinal growth layers in teeth of Peruvian dusky dolphins (''Lagenorhynchus obscurus'')|journal=Canadian Journal of Zoology|volume=67|issue=9|pages=2120–2125|doi=10.1139/z89-301|bibcode=1989CaJZ...67.2120M}}</ref> Newborns have an average length of {{cvt|91.2|cm|ft|abbr=on}} and a weight of {{cvt|9.6|kg|lb|abbr=on}}  off [[Peru]].<ref name="demography"/>{{rp|40}}

The species has a somewhat stocky build, with a short, pointed [[Rostrum (anatomy)|beak]], curved dorsal fin and flippers, and between 108 and 144 small, conical teeth.<ref name="Jefferson">{{cite book|last1=Jefferson|first1=Thomas A.|last2=Webber|first2=Marc A.|last3=Pitman|first3=Robert L.|year=2015|title=Marine Mammals of the World: A Comprehensive Guide to Their Identification|publisher=Academic Press|edition=2nd|pages=293–296|isbn=978-0-12-409542-7}}</ref> It has a distinctive colouration that resembles the Pacific white-sided dolphin, with a dark-grey or black upper side, orbital (eye) region, and beak; a light-grey face, chest area, and [[Flank (anatomy)|flank]] patch; and a white underside. The flank patch has an extension or blaze that reaches over the back and towards the [[Blowhole (anatomy)|blowhole]].<ref name="HMM"/><ref name="Perrin"/><ref name="Jefferson"/> The dorsal fin is darker in front and lightens towards the back; the flippers are light-grey with darker edges.<ref name="Jefferson"/> The dusky dolphin differs from the Pacific white-sided dolphin in having a more slender skull<ref name="demography"/>{{rp|37}} and a shorter blaze.<ref name="Perrin"/>

==Distribution==
[[File:Anim1772 - Flickr - NOAA Photo Library.jpg|thumb|right|Dusky dolphins [[cetacean surfacing behavior|leaping]] off [[Kaikōura Peninsula|Kaikōura]]|alt=Three dolphins airborne]]
The dusky dolphin has a discontiguous range in the [[Southern Hemisphere]];<ref name="Jefferson"/> including the coasts of western and southeastern South America, southwestern Africa, New Zealand, and some oceanic islands in the south Atlantic and Indian Ocean. It has also been sighted off southern Australia.<ref name="Perrin">{{cite book|last1=Waerebeek|first1=K. V.|last2=Wursi|first2=B.|chapter=Dusky Dolphin ''Lagenorhynchus obscurus''|pages=335–337|title=Encyclopedia of Marine Mammals|editor1-last=Perrin|editor1-first=W. F.|editor2-last=Wursig|editor2-first=B.|editor3-last=Thewissen|editor-first3=J. G. M.|publisher=Academic Press|edition=2nd|year=2008|isbn=978-0-12-373553-9}}</ref> 

Dusky dolphins can be found throughout New Zealand waters and are most common along the eastern coasts, between [[East Cape]] on the [[North Island]] and [[Timaru]]/[[Oamaru]] on the [[South Island]]. They are sighted year-round in the stable, cold waters off the coast of the northern [[Canterbury Region]].<ref name="Gaskin 1972">{{cite book|last=Gaskin|first=D. E.|year=1972|title=Whales, Dolphins and Seals with Special Reference to the New Zealand Region|publisher=Heinemann Educational|pages=124–126|isbn=0-423-62285-4}}</ref> Off South America, they range from southern Peru to [[Cape Horn]] in the Pacific and then up to around [[36th parallel south|36°S]] in the Atlantic, along with the [[Falkland Islands]],<ref name="Perrin"/> where they are thought to be less abundant.<ref>{{cite journal|last1=Weir|first1=C. R.|last2=Black|first2=A.|year=2018|title=Records of the dusky dolphin (''Lagenorhynchus obscurus'') in the Falkland Islands, including associations with Peale's dolphin (''L. australis'')|journal= Marine Biodiversity Records|volume=11|issue=18|article-number=18 |doi=10.1186/s41200-018-0153-2|doi-access=free |bibcode=2018MBdR...11...18W }}</ref> Off Africa, the dusky dolphin ranges from [[Lobito Bay]], Angola, in the north to [[False Bay]], South Africa, in the south.<ref name="Perrin"/> Within Australian waters, dusky dolphins have been recorded off [[Kangaroo Island]], eastern [[Tasmania]], and in the [[Bass Strait]],<ref name="Menkhorst">{{cite book|last=Menkhorst|first=Peter|title=A Field Guide to Mammals of Australia|publisher=Oxford University Press|location=South Melbourne, Victoria|year=2001|pages=226–227|isbn=0-19-550870-X}}</ref> although they are uncommon and may be transients from New Zealand.<ref>{{cite journal |last1=Gill |first1=Peter C. |title=Confirmed sightings of dusky dolphins (''Lagenorhynchus Obscurus'') in southern Australian waters |last2=Ross |first2=Graham J. B. |last3=Dawbin |first3=William H. |last4=Wapstra |first4=Hans |journal=Marine Mammal Science |volume=16 |issue=2 |pages=452–459 |year=2000 |doi=10.1111/j.1748-7692.2000.tb00937.x|bibcode=2000MMamS..16..452G }}</ref> Dusky dolphins are also found around the islands of [[Tristan da Cunha]], [[Prince Edward Islands|Prince Edward]], [[Crozet Islands|Crozet]], [[Île Amsterdam]], and [[Île Saint-Paul]].<ref name="HMM"/><ref name="Jefferson"/>

==Ecology and behaviour==
[[File:Large pod of Dusky Dolphins in South Bay, Kaikoura.jpg|thumb|right|Large pod of dusky dolphins in South Bay, Kaikōura |alt=Large group of dolphins]]
Dusky dolphins live mostly in coastal waters within the [[continental shelf]] and prefer cool, upwelling waters, as well as cold currents.<ref name="Jefferson"/><ref name="Perrin"/><ref name="Gaskin 1972"/> Dolphins off Argentina and New Zealand move to and from shore between day and night and between seasons.<ref name="Perrin"/> Seasonal migrations have been recorded between [[Kaikōura Peninsula|Kaikōura]] and [[Admiralty Bay (New Zealand)|Admiralty Bay]], New Zealand.<ref name="Orbach2018"/><ref name="Pearson2009"/> Around Kaikōura, the majority of individuals have only been seen once in the area over a 30-year period, suggesting high levels of immigration and emigration.<ref name="Orbach2018">{{cite journal|last1=Orbach|first1=D. N.|last2=Pearson|first2=H. C.|last3=Engelhaupt|first3=A.|last4=Deutsch|first4=S.|last5=Srinivasan|first5=M.|last6=Weir|first6=J. S.|last7=Yin|first7=S.|last8=Würsig|first8=B.|year=2018|title=Long-term assessment of spatio-temporal association patterns of dusky dolphins (''Lagenorhynchus obscurus'') off Kaikōura, New Zealand|journal=Aquatic Mammals|volume=44|issue=6|pages=608–619|doi=10.1578/AM.44.6.2018.608|bibcode=2018AqMam..44..608O }}</ref> Dusky dolphins were recorded swimming up to {{convert|10|m/s|kph mph}}<ref>{{cite journal|last1=Davis|first1=R. W.|last2=Fiori|first2=L|last3=Würsig|first3=B|last4=Orbach|first4=D. N.|year=2024|title=Drag reduction and locomotory power in dolphins: Gray's paradox revealed|journal=Journal of the Royal Society Interface|volume=21|issue=218|article-number=20240227 |doi=10.1098/rsif.2024.0227|pmid=39257283 |pmc=11463224 }}</ref> and diving up to {{convert|130|m|ft|abbr=on}}.<ref name="Perrin"/>

Most studies of foraging and social behaviour in the species have been conducted at Kaikōura, Admiralty Bay, and [[San Jorge Gulf]], Argentina.<ref name="Pearson2009"/><ref name="function"/>{{rp|565}} Dusky dolphins live in a [[fission–fusion society]] and individuals move in and out of groups depending on social and environmental conditions.<ref name="Pearson2009"/><ref name="Pearson2017">{{cite journal|last1=Pearson|first1=H. C.|last2=Markowitz|first2=T. M.|last3=Weir|first3=J. S.|last4=Würsig|first4=B.|year=2017|title=Dusky dolphin (''Lagenorhynchus obscurus'') social structure characterized by social fluidity and preferred companions|journal=Marine Mammal Science|volume=33|issue=1|pages=251–276|doi=10.1111/mms.12370|bibcode=2017MMamS..33..251P }}</ref><ref name="Degrati2019"/>{{rp|1}} At Kaikōura, group sizes can reach 1,000 dolphins,<ref name="function"/>{{rp|565}} while in Admiralty Bay, they peak at around 50 dolphins.<ref name="Pearson2009"/> Groups form for different activities, including foraging, resting, travelling, and socialising.<ref name="Degrati2019"/>{{rp|3}} At Kaikōura, groups are larger when resting and smaller when foraging,<ref name="function"/>{{rp|565}} but the reverse is true at San Jorge Gulf.<ref name="Degrati2019">{{cite journal|last1=Degrati|first1=M.|last2=Coscarella|first2=M. A.|last3=Crespo|first3=E. A.|last4=Dans|first4=S. L.|year=2019|title=Dusky dolphin group dynamics and association patterns in Península Valdés, Argentina|journal=Marine Mammal Science|volume=35|issue=2|pages=416–433|doi=10.1111/mms.12536|bibcode=2019MMamS..35..416D}}</ref>{{rp|5}}<ref>{{cite journal|last1=Degrati|first1=M|last2=Dans|first2=S|last3=Pedraza|first3=S. N.|last4=respo|first4=E. A.|last5=Garaffo|first5=G. V.|year=2008|title=Diurnal behavior of dusky dolphins, ''Lagenorhynchus obscurus'', in Golfo Nuevo, Argentina|journal=Journal of Mammalogy|volume=89|issue=5|pages=1241–1247|doi=10.1644/07-MAMM-A-110.1|hdl=11336/100653|hdl-access=free}}</ref> At Admiralty Bay, foraging leads to larger aggregations; resting does not appear to correlate with group size.<ref name="Pearson2009">{{cite journal|last1=Pearson|first1=H. C.|year=2009|title=Influences on dusky dolphin (''Lagenorhynchus obscurus'') fission-fusion dynamics in Admiralty Bay, New Zealand|journal=Behavioral Ecology and Sociobiology|volume=63|issue=10 |pages=1437–1446|doi=10.1007/s00265-009-0821-7|bibcode=2009BEcoS..63.1437P }}</ref> Most associations between individuals are weak but long-term bonds do occur.<ref name="Pearson2017"/>

Dusky dolphins can be found in mixed groups with other cetacean species, including [[common dolphin]]s, [[southern right whale]]s, [[Risso's dolphin]]s, [[southern right whale dolphin]]s, and [[pilot whales]].<ref name="behavior"/>{{rp|882}}<ref name="demography">{{cite book|last1=Cipriano|first1=F.|last2=Webber|first2=M.|chapter=Dusky Dolphin Life History and Demography|pages=21–48|editor1-last=Würsig|editor1-first=B.|editor2-last=Würsig|editor2-first=M.|title=The Dusky Dolphin: Master Acrobat off Different Shores|publisher=Academic Press|year=2010|isbn=978-0-12-373723-6}}</ref>{{rp|41}}<ref>{{cite journal|last1=Curcio|first1=N. S.|last2=Svendsen|first2=G. M.|last3=Bartes|first3=S|last4=Romero|first4=M. A.|last5=Arias|first5=M|last6=González|first6=R. A.|last7=Dans|first7=S. L.|year=2023|title=Group dynamics and activity patterns of two dolphin species, the common dolphin (''Delphinus delphis'') and dusky dolphin (''Lagenorhynchus obscurus'') in direct sympatry|journal=Journal of Mammalogy|volume=104|issue=5|pages=1096–1111|doi=10.1093/jmammal/gyad045}}</ref> Off Argentina, they have been found around [[bottlenose dolphin]]s, but seem to ignore them.<ref name="behavior"/>{{rp|882}} Dusky dolphins also feed with non-cetacean species such as [[South American sea lion]]s, [[kelp gull]]s, [[cormorant]]s, [[tern]]s, [[shearwater]]s, [[petrel]]s, [[albatross]]es, and [[Magellanic penguin]]s off Argentina, and [[Australasian gannet]]s, shearwaters, terns, gulls, [[spotted shag]]s, [[New Zealand fur seal]]s, [[spiny dogfish]], and [[common thresher]]s off New Zealand.<ref name="Vaughn2007">{{cite journal|last1=Vaughn|first1=R. L.|last2=Shelton|first2=D. E.|last3=Timm|first3=L. L.|last4=Watson|first4=L. A.|last5=Würsig|first5=B.|year=2007|title=Dusky dolphin (''Lagenorhynchus obscurus'') feeding tactics and multi-species associations|journal=New Zealand Journal of Marine and Freshwater Research|volume=41|issue=4|pages=391–400|doi=10.1080/00288330709509929|bibcode=2007NZJMF..41..391V }}</ref><ref name="daylight"/>{{rp|123}}

===Vocalisations and echolocation===
Like other oceanic dolphins, dusky dolphins produce three basic types of sounds: [[Animal echolocation|echolocative]] click trains, burst pulses and tonal whistles.<ref name="Vaughn-Hirshorn2012">{{cite journal|last1=Vaughn-Hirshorn|first1=R. L.|last2=Hodge|first2=K. B.|last3=Würsig|first3=B.|last4=Sappenfield|first4=R. H.|last5=Lammers|first5=M. O.|last6=Dudzinski|first6=K. M.|year=2012|title=Characterizing dusky dolphin sounds from Argentina and New Zealand|journal=The Journal of the Acoustical Society of America|volume=132|issue=1|pages=498–506|doi=10.1121/1.4728191|pmid=22779496 |bibcode=2012ASAJ..132..498V }}</ref><ref name="acoustics"/>{{rp|77}} Their echolocation signals are quick and [[broadband]], much like in other whistle-producing species,<ref name="acoustics"/>{{rp|95}} and have two peaks: between 40 and 50&nbsp;kHz at low frequency and between 80 and 110&nbsp;kHz at high frequency.<ref name="echolocation">{{cite journal |last1=Au |first1=W. W. L. |last2=Würsig |first2=B.|title=Echolocation signals of dusky dolphins (''Lagenorhynchus obscurus'') in Kaikōura, New Zealand. |journal=The Journal of the Acoustical Society of America |volume=115 |issue=5 Pt 1 |pages=2307–2313 |year=2004 |pmid=15139642 |doi=10.1121/1.1690082|bibcode=2004ASAJ..115.2307A }}</ref> Burst pulses are similar to echolocation signals but the pauses between clicks are shorter, at 0.5–10 milliseconds.<ref name="acoustics"/>{{rp|81}} Off New Zealand and Argentina, they often consist of 2–14 clicks in succession and appear to be important for communication.<ref name="Vaughn-Hirshorn2012"/> Whistling is more common when dusky dolphins mingle with other dolphin species such as common dolphins.<ref name="acoustics">{{cite book|last1=Au|first1=W. W. L.|last2=Lammer|first2=M. O.|last3=Yin|first3=S.|chapter=Acoustics of Dusky Dolphins (''Lagenorhynchus obscurus'')|pages=75–98|editor1-last=Würsig|editor1-first=B.|editor2-last=Würsig|editor2-first=M.|title=The Dusky Dolphin: Master Acrobat off Different Shores|publisher=Academic Press|year=2010|isbn=978-0-12-373723-6}}</ref>{{rp|78}}

===Foraging===
[[File:Dusky dolphins.jpg|thumb|right|Dusky dolphins swimming at the surface|alt=Two dolphins at the water surface]]
Dusky dolphins mainly feed on fish and squid. Fish species eaten include anchovies, [[lantern fish]], [[pilchard]]s, [[sculpin]]s, [[hake]]s, [[horse mackerel]], [[Blue grenadier|hoki]], and [[Red codling|red cod]]; the squids they prey on include those of the genera ''[[Nototodarus]]'', ''[[Todarodes]]'', and ''[[Loligo]]''.<ref name="Perrin"/> Dusky dolphins are generally coordinated hunters, and their flexible foraging strategies can change depending on the environment.<ref>{{cite book|last1=Dahood|first1=A. D.|last2=Beniot-Bird|first2=K. J.|chapter=Dusky Dolphins Foraging at Night|pages=99–114|editor1-last=Würsig|editor1-first=B.|editor2-last=Würsig|editor2-first=M.|title=The Dusky Dolphin: Master Acrobat off Different Shores|publisher=Academic Press|year=2010|isbn=978-0-12-373723-6}}</ref>{{rp|103}} In the [[Kaikōura Canyon]], where deep oceanic waters meet the coast, they forage at night in [[deep scattering layer]]s. Dolphins travel to the hunting site individually and form groups when in the layer. The number of individuals in these groups ranges up to five members and decreases to single dolphins as the layer descends down the water column.<ref name="Benoit 2004">{{cite journal|author1=Benoit-Bird, K. J.|author2=Würsig, B.|author3=McFadden, C. J.|year=2004|title=Dusky dolphin (''Lagenorhynchus obscurus'') foraging in two different habitats: active acoustic detection of dolphins and their prey|journal=Marine Mammal Science|volume=20|issue=2|pages=215–231|doi=10.1111/j.1748-7692.2004.tb01152.x|bibcode=2004MMamS..20..215B |url=http://people.oregonstate.edu/~benoitbk/reprints/dusky%20foraging%20mms.pdf|access-date=3 February 2011|archive-date=27 November 2010|archive-url=https://web.archive.org/web/20101127160916/http://people.oregonstate.edu/~benoitbk/reprints/dusky%20foraging%20mms.pdf|url-status=live}}</ref>

In San Jorge Gulf, between October and January, and Admiralty Bay, between August and November, dusky dolphins herd schools of fish into [[bait ball]]s during the day.<ref name="daylight">{{cite book|last1=Dahood|first1=A. D.|last2=Beniot-Bird|first2=K. J.|chapter=Dusky Dolphins Foraging in Daylight|pages=115–132|editor1-last=Würsig|editor1-first=B.|editor2-last=Würsig|editor2-first=M.|title=The Dusky Dolphin: Master Acrobat off Different Shores|publisher=Academic Press|year=2010|isbn=978-0-12-373723-6}}</ref>{{rp|116–119}}<ref name="Vaughn2007"/> They use the water surface as a barrier for the fish as they circle around them.<ref name="behavior"/>{{rp|885–886}}<ref name="daylight"/>{{rp|119–120}} and may also scare them with sound or by flashing their white bellies.<ref name="daylight"/>{{rp|121}} The larger the group, the more effective dolphins are in herding the school.<ref name="Vaughn"/>{{rp|219}} These hunts may also involve other species, including other dolphins, [[seabird]]s, [[shark]]s, and [[pinniped]]s.<ref name="Vaughn">{{cite journal|last1=Vaughn|first1=R.|last2=Würsig|first2=B.|last3=Packard|first3=J.|year=2009|title=Dolphin prey herding: Prey ball mobility relative to dolphin group and prey ball sizes, multispecies associates, and feeding duration|journal=Marine Mammal Science|volume=26|issue=1|pages=213–225|doi=10.1111/j.1748-7692.2009.00317.x}}</ref>{{rp|213}}<ref name="foodweb"/>{{rp|65}} Common dolphins seem to participate in herding with dusky dolphins. By contrast, pinnipeds, sharks, and other predatory fish [[Kleptoparasitism|take]] food without helping in the hunt,<ref name="foodweb">{{cite book|last1=Dans|first1=S. L.|last2=Crespo|first2=E. A.|last3=Koen-Alonso|first3=M.|last4=Markowitz|first4=T. M.|last5=Vera|first5=B. B.|last6=Dahood|first6=A. D.|chapter=Dusky Dolphins Trophic Ecology: Their Role in the Food Web|pages=49–74|editor1-last=Würsig|editor1-first=B.|editor2-last=Würsig|editor2-first=M.|title=The Dusky Dolphin: Master Acrobat off Different Shores|publisher=Academic Press|year=2010|isbn=978-0-12-373723-6}}</ref>{{rp|65}} and foraging by diving birds like gannets can make herding more strenuous for dolphins.<ref name="Vaughn"/>{{rp|219}} From May to October in San Jorge Gulf and between May and July at Admiralty Bay, dusky dolphins hunt deeper below the surface.<ref name="Vaughn2007"/><ref name="Degrati2012">{{cite journal|last1=Degrati|first1=M.|last2=Dans|first2=S. L.|last3=Garaffo|first3=G. V.|last4=Crespo|first4=E. A.|year=2012|title=Diving for food: a switch of foraging strategy of dusky dolphins in Argentina|journal=Journal of Ethology|volume=30|issue=3|pages=361–367|doi=10.1007/s10164-012-0333-1 |hdl=11336/72954 }}</ref>

===Reproduction and parenting===
{{See also|Dolphin#Reproduction and sexuality}}
[[File:Mating dolphins underwater - panoramio.jpg|thumb|right|Dusky dolphins mating|alt=Dusky dolphin matings with male under female]]
Dusky dolphins reach sexual maturity between four and eight years depending on the region.<ref name="mating"/>{{rp|170}} They have a [[polygynandrous]] mating system in which both males and females mate with multiple partners.<ref name="mating"/>{{rp|151–152}} Hence, males have large testes for [[sperm competition]].<ref name="mating"/>{{rp|164}}<ref name="cetacean"/>{{rp|310–311}} Mating groups typically consist of multiple males and one female; at Kaikōura, groups usually have a total of five members but can vary from two to fifteen.<ref name="Orbach2014">{{cite journal|last1=Orbach|first1=D. N.|last2=Packard|first2=J. M.|last3=Würsig|first3=B.|year=2014|title=Mating group size in dusky dolphins (''Lagenorhynchus obscurus''): costs and benefits of scramble competition|journal=Ethology|volume=120|issue=8|pages=804–815|doi=10.1111/eth.12253|bibcode=2014Ethol.120..804O }}</ref> They can be found in both shallow and deep water but more often congregate near shore.<ref name="mating">{{cite book|last1=Markowitz|first1=T. M.|last2=Markowitz|first2=W. J.|last3=Morton|first3=L. M.|chapter=Mating Habits of New Zealand Dusky Dolphins|pages=151–176|editor1-last=Würsig|editor1-first=B.|editor2-last=Würsig|editor2-first=M.|title=The Dusky Dolphin: Master Acrobat off Different Shores|publisher=Academic Press|year=2010|isbn=978-0-12-373723-6}}</ref>{{rp|162}} 

Within a mating group, the males pursue a female in a high-speed chase. Females appear to prefer males with great speed and agility over size, strength, or aggression, and try to evade males that are less energetic and lack social skills.<ref name="mating"/>{{rp|164, 170, 175}} Males also form alliances to capture females.<ref name="mating"/>{{rp|167–169}} Off Kaikōura, dusky dolphins have been found to have scars and notches on their dorsal fins, thought to be caused by aggression between males and towards females during mating.<ref>{{cite journal|last1=Kügler|first1=A|last2=Orbach|first2=D. N.|year=2014|title=Sources of notch and scar patterns on the dorsal fins of dusky dolphins (''Lagenorhynchus obscurus'')|journal=Aquatic Mammals|volume=40|issue=3|pages=260–273|doi=10.1578/AM.40.3.2014.260|bibcode=2014AqMam..40..260K}}</ref> A study in the same area did not observe aggression in mating groups; males did not fight among themselves nor control who could be part of the group but did interfere with copulations.<ref>{{cite journal|last1=Orach|first1=D. N.|last2=Eaton|first2=J.|last3=Fiori|first3=L.|last4=Piwetz|first4=S.|last5=Wier|first5=J. S.|last6=Würsig|first6=M.|last7=Würsig|first7=B.|year=2020|title=Mating patterns of dusky dolphins (''Lagenorhynchus obscurus'') explored using an unmanned aerial vehicle|journal=Marine Mammal Science|volume=36|issue=4|pages=1097–1110|doi=10.1111/mms.12695|bibcode=2020MMamS..36.1097O }}</ref> During mating, female dusky dolphins usually take the top position.<ref name="mating"/>{{rp|170}} Dusky dolphins also engage in [[non-reproductive sexual behaviour]], including [[Homosexual behavior in animals|homosexual behaviour]], perhaps for greeting, communication, or strengthening social bonds, and there is no high-speed chasing.<ref name="mating"/>{{rp|175}}

Female dusky dolphins off the coast of Peru were found to have gestation periods of over 12 months.<ref name="HMM"/> Calves are born during the spring (August to October) off Peru and in summer (November to February) off Argentina, South Africa, and New Zealand.<ref name="Jefferson"/> Females with calves tend to congregate in [[Crèche (zoology)|nursery groups]], which may provide them more time to rest and facilitate socialisation among the young. Calves learn to hunt from their mothers, and nursery groups typically forage in shallow water because deeper water is too dangerous for young, particularly because of predators.<ref name="calf">{{cite book|last1=Weir|first1=J.|last2=Deutsch|first2=S.|last3=Pearson|first3=H. C.|chapter=Dusky Dolphin Calf Rearing|pages=177–194|editor1-last=Würsig|editor1-first=B.|editor2-last=Würsig|editor2-first=M.|title=The Dusky Dolphin: Master Acrobat off Different Shores|publisher=Academic Press|year=2010|isbn=978-0-12-373723-6}}</ref>{{rp|183, 188–191}} Nursery groups keep away from mating groups, as adult males will aggressively chase mothers and leave calves dazed and vulnerable.<ref name="mating"/>{{rp|174}}<ref name="calf"/>{{rp|185}} Conversely, females with calves will associate with non-breeding adults in large groups.<ref name="cetacean">{{cite book|last1=Markowitz|first1=T. M.|last2=Markowitz|first2=W. J.|last3=Würsig|first3=B|last4=Orbach|first4=D. N.|year=2023|title=Sex in Cetaceans|chapter=Sociosexual Behavior of Nocturnally Foraging Dusky and Spinner Dolphins|editor1-last=Würsig|editor1-first=B|editor2-last=Orbach|editor2-first=D. N.|publisher=Springer|pages=307–325|isbn=978-3-031-35650-6}}</ref>{{rp|318}} Near Peru, calves may be weaned around 12 months, and the female can breed again less than four months after that.<ref name="HMM"/>

===Aerial behaviour===
[[File:DuskyJump.jpg|thumb|right|Dusky dolphins leaping and flipping|alt=Two dolphins vertically leaping and flipping, one pointing upward, the other pointing downward]]
Dusky dolphins perform several kinds of [[Cetacean surfacing behaviour|leaping displays]], which are classed into noisy, clean, acrobatic, and coordinated. Noisy leaps end in splashes upon re-entry and include back slaps, head slaps, side slaps, tail slaps and belly flops. For clean leaps, the dolphin leaps with the body vertical and lands with little to no splashing. These include headfirst re-entries and "humpings", both of which involve the dolphin leaving the water, arching its back and then flipping the tail before plunging headfirst. For humpings, the dolphin is arched after the nose enters the water and before the tail leaves. Acrobatic leaps are complex and consist of head-over-tail flips or somersaults and spins, both of which can cause splashes. Coordinated leaps are synchronised between two or more individuals.<ref name="behavior"/>{{rp|879}}<ref name="function">{{cite journal|last1=Pearson|first1=H. C.|year=2017|title=Unravelling the function of dolphin leaps using the dusky dolphin (''Lagenorhynchus obscurus'') as a model species|journal=Behaviour|volume=154|issue=5|pages=563–581|doi=10.1163/1568539X-00003434|jstor=26363105}}</ref>{{rp|569}}<ref name="Deutsch2014"/>{{rp|1563}} 

These leaps probably have several functions. One study in Admiralty Bay found that clean leaping may play a role in hunting prey, with coordinated leaps marking the end of the hunts and also perhaps serving a social function. Noisy leaps appear to cause more activity among the group.<ref name="function"/>{{rp|573–575}} The ability to make these leaps is apparently not inborn but learnt. Calves appear to learn jump styles in the following order: noisy leaps, clean leaps, coordinated leaps, and acrobatic leaps.<ref name="calf"/>{{rp|190–191}}<ref name="Deutsch2014">{{cite journal|last1=Deutsch|first1=S.|last2=Pearson|first2=H.|last3=Würsig|first3=B.|year=2014|title=Development of leaps in dusky dolphin (''Lagenorhynchus obscurus'') calves|journal=Behaviour|volume=151|issue=11|pages=1555–1577|doi=10.1163/1568539X-00003200|jstor=24526341}}</ref>{{rp|1570}}

===Mortality and health===
Dusky dolphins may live 26–30 years.<ref name="demography"/>{{rp|39}} They are preyed on by [[orca]]s and sharks and may swim into shallower water near shore where there is less risk of being attacked from below or the sides.<ref name="behavior">{{cite journal | last1 =Würsig| first1 =B. | last2 =Würsig| first2 =M. | year =1980| title = Behavior and ecology of the dusky dolphin, ''Lagenorhynchus obscurus'', in the South Atlantic | url = http://fishbull.noaa.gov/77-4/wursig.pdf | journal = Fishery Bulletin | volume = 77 | pages = 871–890 | access-date = 3 February 2011 | archive-date = 1 April 2011 | archive-url = https://web.archive.org/web/20110401080540/http://fishbull.noaa.gov/77-4/wursig.pdf | url-status = live }}</ref>{{rp|887–888}} Dusky dolphins are also susceptible to internal [[parasitism]] by [[nematode]], [[cestode]], and [[trematode]] species.<ref name="foodweb"/>{{rp|67}}<ref name="VanWaerebeek1993">{{cite journal | last1 = Van Waerebeek | first1 = K.| last2 = Reyes | first2 = J. C. | last3 = Alfaro | first3 = J.| year = 1993 | title = Helminth parasites and phoronts of dusky dolphins ''Lagenorhynchus obscurus'' (Gray, 1828) from Peru | url = http://www.aquaticmammalsjournal.org/share/AquaticMammalsIssueArchives/1993/Aquatic_Mammals_19_3/19-03_VanWaerebeek.pdf | journal = Aquatic Mammals | volume = 19 | issue = 3 | pages = 159–169 | access-date = 3 February 2011 | archive-date = 4 September 2011 | archive-url = https://web.archive.org/web/20110904061422/http://www.aquaticmammalsjournal.org/share/AquaticMammalsIssueArchives/1993/Aquatic_Mammals_19_3/19-03_VanWaerebeek.pdf }}</ref><ref name="Dans1999">{{cite journal|last1=Dans|first1=S. L.|last2=Reyes|first2=L. M.|last3=Pedraza|first3=S. N.|last4=Raga|first4=J. A.|last5=Crespo|first5=E. A.|year=1999|title=Gastrointestinal helminths of the dusky dolphin, ''Lagenorhynchus obscurus'' (Gray, 1828), off Patagonia, in the southwestern Atlantic|journal=Marine Mammal Science|volume=15|issue=3|pages=649–660|doi=10.1111/j.1748-7692.1999.tb00834.x|bibcode=1999MMamS..15..649D }}</ref> Off Peru, parasites include those of the genera ''[[Brachycladiidae|Nasitrema]]'' and ''[[Anisakis]]'', and the species ''[[Eucestoda#Common infective species|Phyllobothrium]] delphini'', ''[[Braunina cordiformis]]'', and ''[[Pholeter]] gasterophilus'';<ref name="VanWaerebeek1993"/> a study of dolphins off Patagonia found that the most common parasites were ''[[Anisakis simplex]]'', ''Braunina cordiformis'', and species of the genus ''[[Campululidae|Hadwenius]]''.<ref name="Dans1999"/> Dusky dolphins may suffer tattoo-like skin lesions caused by a  [[poxvirus]],<ref>{{cite journal|last1=Van Bressem|first1=M-F|last2=Van Waerebeek|first2=K|last3=Reyes|first3=J. C.|last4=Dekegal|first4=D|year=1993|title=Evidence of poxvirus in dusky dolphin (''Lagenorhynchus obscurus'') and Burmeister's porpoise (''Phocoena spinipinnis'') from Coastal Peru|journal=Journal of Wildlife Diseases|volume=29|issue=1|pages=109–113|doi=10.7589/0090-3558-29.1.109 |pmid=8383251 }}</ref> as well as genital diseases such as [[ovarian cyst]]s, [[Uterine fibroid|uterine tumour]]s, vaginal stones and testicular lesions.<ref>{{cite journal|last1=Van Bressem|first1=M-F|last2=Van Waerebeek|first2=K|last3=Siebert|first3=U|last4=Wünschmann|first4=A|last5=Chávez-Lisambart|first5=L|last6=Reyes|first6=J. C.|year=2000|title=Genital diseases in the Peruvian dusky dolphin (''Lagenorhynchus obscurus'')|journal=Journal of Comparative Pathology|volume=122|issue=4|pages=266–277|doi=10.1053/jcpa.1999.0369 |pmid=10805980 }}</ref> In a sample of dusky dolphins off Peru, 66% of them had [[genital wart]]s caused by a [[papillomavirus]].<ref>{{cite journal|last1=Van Bressem|first1=M-F|last2=Van Waerebeek|first2=K|last3=Piérard|first3=G. E.|last4=Desaintes|first4=C|year=1996|title=Genital and lingual warts in small cetaceans from coastal Peru|journal=Diseases of Aquatic Organisms|volume=26|pages=1–10|doi=10.3354/dao026001}}</ref>

==Interactions with humans==
[[File:Two dusky dolphins swimming alongside boat.JPG|thumb|right|A pair of dusky dolphins swimming alongside a boat|alt=Two dolphins seen from the side of a boat]]
Dusky dolphins are popular attractions for [[dolphin watching]] tours. In Patagonia, dolphin watching started as an alternative to whale watching, the dusky and [[Commerson's dolphin]]s being the main attractions since 1997. In 2001, 90% of boat trips encountered dusky dolphins, up from 25% two years before.<ref name="Coscarella 2003">{{cite journal | last1 = Coscarella | first1 = M. A. | last2 = Dans | first2 = S. L. | last3 = Crespo | first3 = E. A. | last4 = Pedraza | first4 = S. N. | year = 2003 | title = Potential impact of unregulated dolphin watching activities in Patagonia | journal = Journal of Cetacean Research and Management | volume = 5 | pages = 77–84 | doi = 10.47536/jcrm.v5i1.829 | doi-access = free }}</ref> Dusky dolphin watching is also popular in New Zealand, whose dolphin-watching industry started in the late 1980s as a side attraction to sperm whale watching. By 2010, the number of official whale- and dolphin-watching tour operators in the country had risen to around 75.<ref name="tourism">{{cite book|last1=Markowitz|first1=T. M.|last2=Dans|first2=S. L.|last3=Crespo|first3=E. A.|last4=Lundquist|first4=D. L.|last5=Duprey|first5=N. M. T.|chapter=Human Interactions with Dusky Dolphins: Harvest, Fisheries, Habitat Alteration, and Tourism|pages=211–244|editor1-last=Würsig|editor1-first=B.|editor2-last=Würsig|editor2-first=M.|title=The Dusky Dolphin: Master Acrobat off Different Shores|publisher=Academic Press|year=2010|isbn=978-0-12-373723-6}}.</ref>{{rp|235–236}}

The presence of vessels has the potential to disrupt dusky dolphin activities. Dolphins may lose energy interacting with or avoiding vessels—energy they could use for socialising and feeding. Boats also create [[noise pollution]], which makes it harder for dolphins to communicate.<ref>{{cite journal|last1=Lundquist|first1=D.|last2=Gemmell|first2=N. J.|last3=Würsig|first3=B.|year=2012|title=Behavioural responses of dusky dolphin groups (''Lagenorhynchus obscurus'') to tour vessels off Kaikōura, New Zealand|journal=PLOS ONE|volume=7|issue=7|article-number=e41969|doi=10.1371/journal.pone.0041969|doi-access=free|pmid=22844536|pmc=3402466 |bibcode=2012PLoSO...741969L|hdl=1969.1/180588|hdl-access=free}}</ref><ref>{{cite journal|last1=Dans|first1=S. L.|last2=Crespo|first2=E. A.|last3=Pedraza|first3=S. N.|last4=Degrati|first4=M.|last5=Garaffo|first5=G.|year=2008|title=Dusky dolphin and tourist interaction: Effect on diurnal feeding behavior|journal=Marine Ecology Progress Series|volume=369|pages=287–296|doi=10.3354/meps07629|bibcode=2008MEPS..369..287D }}</ref> As such, authorities have imposed regulations on tours, including limits on the number of permits as well as guidelines on approaching the animals.<ref name="tourism"/>{{rp|241}}<ref>{{cite web|url=https://wwhandbook.iwc.int/en/country-profiles/argentina|access-date=4 March 2025|title=Argentina|website=Whale Watching Handbook}}</ref> Dusky dolphins can also benefit from encounters with boats by riding the waves they produce (bow-riding), which saves energy while travelling.<ref>{{cite journal|last1=Fiori|first1=L|last2=Davies|first2=R. W.|last3=Würsig|first3=B|last4=Orbach|first4=D. N.|year=2024|title=Energetic savings of bow-riding dolphins|journal=Scientific Reports|volume=14|issue=1|page=30056|doi=10.1038/s41598-024-81920-y|pmid=39627448|pmc=11615280|bibcode=2024NatSR..1430056F}}</ref>

The building of [[Aquaculture in New Zealand|mussel farms]] in [[Admiralty Bay (New Zealand)|Admiralty Bay]] seems to have led to a decline in the number and group size of dolphins passing through, and they herd prey less when near the farms.<ref>{{cite journal|last1=Pearson|first1=H. C.|last2=Vaughn-Hirshorn|first2=R. L.|last3=Srinivasan|first3=M.|last4=Würsig|first4=B.|year=2012|title=Avoidance of mussel farms by dusky dolphins (''Lagenorhynchus obscurus'') in New Zealand|journal=New Zealand Journal of Marine and Freshwater Research|volume=46|issue=4|pages=567–574|doi=10.1080/00288330.2012.712977|bibcode=2012NZJMF..46..567P }}</ref><ref>{{cite journal|last1=Piwetz|first1=S.|last2=Pearson|first2=H. C.|last3=Honkus|first3=K. A.|last4=Würsig|first4=B.|year=2024|title=Dusky dolphin (''Lagenorhynchus obscurus'') habitat use in a mussel farming region and changes over time|journal=New Zealand Journal of Marine and Freshwater Research|volume=59 |issue=2 |pages=418–440 |doi=10.1080/00288330.2024.2334287|hdl=11122/14950|hdl-access=free}}</ref> These farms are also obstacles for echolocation. Dolphins rarely enter mussel farms, and when they do they quickly swim through them.<ref name="mussel farm">{{cite journal |last1=Markowitz |first1=Tim M. |last2=Harlin |first2=April D. |last3=Würsig |first3=Bernd |last4=McFadden |first4=Cynthia J. |title=Dusky dolphin foraging habitat: overlap with aquaculture in New Zealand |journal=Aquatic Conservation: Marine and Freshwater Ecosystems |volume=14 |issue=2 |pages=133–149 |year=2004 |doi=10.1002/aqc.602|bibcode=2004ACMFE..14..133M }}</ref>

==Status==
The dusky dolphin is classified as [[Least Concern]] by the [[IUCN Red List]] as many populations appear to be healthy and stable.<ref name="iucn"/> The dusky dolphin is listed in Appendix II of the [[Convention on the Conservation of Migratory Species of Wild Animals]], meaning that it has an "unfavourable conservation status" and may require international cooperation organised by tailored agreements.<ref name="Appendices">"[http://www.cms.int/documents/appendix/Appendices_COP9_E.pdf Appendix II] {{webarchive |url=https://web.archive.org/web/20110611112003/http://www.cms.int/documents/appendix/Appendices_COP9_E.pdf |date=11 June 2011 }}" 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.</ref><ref>{{cite web|title=Appendix I & II of CMS|publisher=the Convention on the Conservation of Migratory Species of Wild Animals|url=https://www.cms.int/en/species/appendix-i-ii-cms#:~:text=Appendix%20II%20covers%20migratory%20species,could%20be%20achieved%20by%20an|access-date=5 January 2025}}</ref> The total population is unknown;<ref name="demography"/>{{rp|24}} off New Zealand, dusky dolphins may number around 12,000,<ref name="Orbach2018"/> and over 6,500 dolphins have been counted from [[Valdés Peninsula]] to [[Puerto Deseado]], Argentina.<ref>{{cite journal|last1=Schiavini|first1=A|last2=Pedraza|first2=S. N.|last3=Crespo|first3=E. A.|last4=González|first4=R|last5=Dans|first5=S. L.|year=1999|title=Abundance of dusky dolphins (''Lagenorhynchus obscurus'') off North and Central Patagonia, Argentina, in spring and a comparison with incidental catch in fisheries|journal=Marine Mammal Science|volume=15|issue=3|pages=828–840|doi=10.1111/j.1748-7692.1999.tb00845.x|bibcode=1999MMamS..15..828S}}</ref> One study found that dusky dolphins in [[Golfo Nuevo]] had an increasing population trend, with an average population growth of over 4% between 2004 and 2022.<ref>{{cite journal|last1=Coronel-Montigel|first1=B. M.|last2=Loizaga|first2=R|last3=Degrati|first3=M|year=2025|title=Understanding the population dynamics of dusky dolphins (''Lagenorhynchus obscurus'') in Golfo Nuevo, Patagonia, through long-term monitoring|journal=Aquatic Conservation: Marine and Freshwater Ecosystems|volume=35|issue=2|article-number=e70072|doi=10.1002/aqc.70072|bibcode=2025ACMFE..35E0072C }}</ref> 

Dusky dolphins may fall victim to the illegal fisheries that kill small cetaceans off Peru and Chile. The expansion of these fisheries could have started in Peru when the [[anchoveta]] fishery collapsed in 1972.<ref name="iucn"/> Dusky dolphins are killed in large numbers (10,000–15,000 per year) for use as shark bait or for human consumption. This has led to a status of [[Vulnerable species|Vulnerable]] for the Peruvian subspecies.<ref>{{cite iucn |author=Mangel, J. |author2=Alfaro-Shigueto, J. |year=2019 |title=''Lagenorhynchus obscurus'' ssp. ''posidonia'' |volume=2019 |article-number=e.T134820643A151580809 |doi=10.2305/IUCN.UK.2019-3.RLTS.T134820643A151580809.en |access-date=17 June 2024}}</ref>  Off New Zealand, gill nets have also been a threat, though [[bycatch]]es seem to have decreased since the 1970s and 1980s.<ref name="Perrin"/> Compared to marine mammals living more to the north, dusky dolphins are less contaminated by [[marine pollution|marine pollutants]] like [[DDT]] and [[persistent organic pollutant]]s.<ref name="tourism"/>{{rp|224}}

==See also==
*[[List of cetaceans]]
*[[Mammals of New Zealand]]

==References==
{{Reflist}}

==External links==
{{Commons}}
*ARKive – [https://web.archive.org/web/20060313170840/http://www.arkive.org/species/GES/mammals/Lagenorhynchus_obscurus/ images and movies of the dusky dolphin ''(Lagenorhynchus obscurus)'']
*[https://uk.whales.org/ Whale and Dolphin Conservation Society]
{{Spoken Wikipedia|date=2025-07-29|En-Dusky-dolphin-article.ogg}}

{{Cetacea|O.}}
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[[Category:Mammals of Patagonia]]
[[Category:Mammals of New Zealand]]
[[Category:Fauna of Tristan da Cunha]]
[[Category:Fauna of the Falkland Islands]]
[[Category:Île Amsterdam]]
[[Category:Cetaceans of the Pacific Ocean]]
[[Category:Cetaceans of the Atlantic Ocean]]
[[Category:Mammals described in 1828|dusky dolphin]]
[[Category:Taxa named by John Edward Gray|dusky dolphin]]
[[Category:Aethalodelphis]]
[[Category:Mammals of Southern Africa]]
[[Category:Western South American coastal fauna]]