Editing American bison (section)

===Social behavior and reproduction===
[[File:Bison - Tall Grass Prairie Preserve - panoramio - Photog (2).jpg|thumb|upright|253px|A herd of American bison grazing at [[Tallgrass Prairie Preserve|Tall Grass Prairie Preserve]] in [[Osage County, Oklahoma|Osage County]], Oklahoma]]
Female bison live in maternal herds which include other females and their offspring. Male offspring leave their maternal herd when around three years old and either live alone or join other males in bachelor herds. Male and female herds usually do not mingle until the breeding season, which can occur from July through September.<ref>{{cite web|url=http://www.nhptv.org/natureworks/americanbison.htm |title=American Bison – Bison bison |publisher=NatureWorks |access-date=February 5, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140217111722/http://www.nhptv.org/natureworks/americanbison.htm |archive-date=February 17, 2014 }}</ref> However, female herds may also contain a few older males. During the breeding season, dominant bulls maintain a small harem of females for mating. Individual bulls "tend" cows until allowed to mate, by following them around and chasing away rival males. The tending bull shields the female's vision with his body so she will not see any other challenging males. A challenging bull may [[bellow (sound)|bellow]] or [[roar]] to get a female's attention, and the tending bull has to bellow or roar back.<ref name="Wolf, 1998"/> The most dominant bulls mate in the first 2–3 weeks of the season.<ref name="Wolf, 1998">{{cite journal|author=Wolff, J. O. |year=1998|title=Breeding strategies, mate choice, and reproductive success in American bison|journal= Okios |volume=83|issue=2|pages=529–544|jstor=3546680|doi=10.2307/3546680|bibcode=1998Oikos..83..529W }}</ref> More subordinate bulls mate with any remaining [[Estrous cycle|estrous]] cow that has not mated yet. Male bison play no part in raising the young.

[[File:Juraparc 06-07-2013 - Buffalo calf.jpg|right|thumb|Calf]]
[[File:Junger Präriebison (Zoo Köln) (1).jpg|left|thumb|A cow suckling calf at the [[Cologne Zoological Garden]] in [[Cologne]], [[Germany]]]]
Bison herds have dominance hierarchies that exist for both males and females. A bison's dominance is related to its birth date.<ref name="Green and Rothstein, 1993">{{cite journal | author = Green W. C. H. R., Aron  | year = 1993 | title = Persistent influences of birth date on dominance, growth and reproductive success in bison | journal = Journal of Zoology | volume = 230 | issue = 2| pages = 177–185 | doi = 10.1111/j.1469-7998.1993.tb02680.x }}</ref> Bison born earlier in the breeding season are more likely to be larger and more dominant as adults.<ref name="Green and Rothstein, 1993"/> Thus, bison are able to pass on their dominance to their offspring as dominant bison breed earlier in the season. In addition to dominance, the older bison of a generation also have a higher fertility rate than the younger ones.<ref name="Green and Rothstein, 1993"/>

Bison mate in August and September; gestation is 285 days. A single reddish-brown calf nurses until the next calf is born. If the cow is not pregnant, a calf will nurse for 18 months. Cows nurse their calves for at least 7 or 8 months, but most calves seem to be weaned before the end of their first year.<ref name=McHugh1958/> At three years of age, bison cows are mature enough to produce a calf. The birthing period for bison in boreal biomes is protracted compared to that of other northern ungulates, such as moose and caribou.<ref>{{cite journal|last1=Jung|first1=Thomas S.|last2=Larter|first2=Nicholas C.|last3=Powell|first3=Todd|date=2018|title=Early and late births in high-latitude populations of free-ranging Bison (Bison bison)|url=https://www.canadianfieldnaturalist.ca/index.php/cfn/article/view/1983|journal=Canadian Field-Naturalist|language=en|volume=132|issue=3|pages=219–222|doi=10.22621/cfn.v132i3.1983|issn=0008-3550|doi-access=free}}</ref>

Bison have a life expectancy around 15 years in the wild and up to 25 years in captivity. However, males and females from a hunted population also subject to wolf predation in northern Canada have been reported to live to 22 and 25 years of age, respectively.<ref>{{cite journal|last=Jung|first=Thomas S.|date=October 8, 2020|title=Longevity in a hunted population of reintroduced American bison (Bison bison)|url=https://doi.org/10.1007/s13364-020-00540-9|journal=Mammal Research|volume=66|pages=237–243|language=en|doi=10.1007/s13364-020-00540-9|s2cid=225126531|issn=2199-241X}}</ref>

Bison have been observed to [[Homosexual behavior in animals#American bisons|display homosexual behaviors]], males much more so than females. In the case of males, it is unlikely to be related to [[dominance (ethology)|dominance]], but rather to social bonding or gaining sexual experience.<ref>Vervaecke H, Roden C. (2006). [https://books.google.com/books?id=KXM3F59y1jkC&pg=PA131 "Going with the herd: same-sex interaction and competition in American bison"]. In: Sommer V, Vasey PL, (editors). ''Homosexual behaviour in animals''. Cambridge University Press. pp. 131–53 {{ISBN|0-521-86446-1}}.</ref>