Editing Orca (section)

===Social structure===
Orcas have complex societies. Only [[elephant]]s and [[higher primate]]s live in comparably complex [[social structure]]s.{{sfn|Heimlich|Boran|2001|p=35}} Due to orcas' complex social bonds, many marine experts have concerns about how humane it is to keep [[Captive killer whales|them in captivity]].<ref>{{cite web |url=http://www.keepwhaleswild.org/ |title=Keep Whales Wild |publisher=Keep Whales Wild |date=January 14, 2011 |access-date=February 16, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20101216065407/http://www.keepwhaleswild.org/ |archive-date=December 16, 2010 }}</ref>

Resident orcas in the eastern North Pacific live in particularly complex and stable social groups. Unlike any other known mammal social structure, resident whales live with their mothers for their entire lives. These family groups are based on [[matriline]]s consisting of the eldest female (matriarch) and her sons and daughters, and the descendants of her daughters, etc. The average size of a matriline is 5.5 animals. Because females can reach age 90, as many as four generations travel together. These matrilineal groups are highly stable. Individuals separate for only a few hours at a time, to mate or forage. The permanent separation of an individual from a resident matriline has only been recorded once, in the case of an orca named [[Luna (orca)|Luna]].{{sfn|NMFS|2005|p=12}}

[[File:Transient Orcas (3727711709).jpg|thumb|A pair of orcas in the [[Pacific Northwest]]]]
Closely related matrilines form loose aggregations called pods, usually consisting of one to four matrilines. Unlike matrilines, pods may separate for weeks or months at a time.{{sfn|NMFS|2005|p=12}} [[DNA]] testing indicates resident males nearly always mate with females from other pods.{{sfn|NMFS|2005|p=39}} Clans, the next level of resident social structure, are composed of pods with similar dialects, and common but older maternal heritage. Clan ranges overlap, mingling pods from different clans.{{sfn|NMFS|2005|p=12}} The highest association layer is the community, which consists of pods that regularly associate with each other but share no maternal relations or dialects.<ref>{{cite book|last1=Ford|first1= J. K. B.|last2=Ellis|first2= G. M.|last3=Balcomb|first3= K. C.|year=1999|title=Killer Whales: The Natural History and Genealogy of ''Orcinus orca'' in British Columbia and Washington State|publisher=University of British Columbia Press|page=25|isbn=978-0774804691}}</ref>

Transient pods are smaller than resident pods, typically consisting of an adult female and one or two of her offspring. Males typically maintain stronger relationships with their mothers than other females. These bonds can extend well into adulthood. Unlike residents, extended or permanent separation of transient offspring from natal matrilines is common, with juveniles and adults of both sexes participating. Some males become "rovers" and do not form long-term associations, occasionally joining groups that contain reproductive females.{{sfn|NMFS|2005|p=13}} As in resident clans, transient community members share an acoustic repertoire, although regional differences in vocalizations have been noted.{{sfn|NMFS|2005|p=14}}

As with residents and transients, the lifestyle of these whales appears to reflect their diet; fish-eating orcas off Norway have resident-like social structures, while mammal-eating orcas in Argentina and the [[Crozet Islands]] behave more like transients.{{sfn|Ford|Ellis|Balcomb|2000|p=27}}

Orcas of the same sex and age group may engage in physical contact and synchronous surfacing. These behaviours do not occur randomly among individuals in a pod, providing evidence of "friendships".<ref>{{cite journal|author=Weiss|first1= M. N.|display-authors=etal|year=2021|title=Age and sex influence social interactions, but not associations, within a killer whale pod|journal=Proceedings of the Royal Society B: Biological Sciences|volume=288|issue=1953|doi=10.1098/rspb.2021.0617|pmid=34130498|pmc=8206696|hdl=10871/125706|hdl-access=free}}</ref><ref>{{cite journal|author=Lesté-Lasserre|first1=Christa|date=June 17, 2021|title=Killer whales form killer friendships, new drone footage suggests|journal=Science|url=https://www.science.org/content/article/killer-whales-form-killer-friendships-new-drone-footage-suggests|access-date=June 18, 2021|archive-date=December 5, 2022|archive-url=https://web.archive.org/web/20221205121706/https://www.science.org/content/article/killer-whales-form-killer-friendships-new-drone-footage-suggests|url-status=live}}</ref>