Editing Testicle (section)

===Size===
[[Image:Rabbit testis.jpg|thumb|Cross section of rabbit testis, photographed in [[bright-field microscopy]] at 40× magnification]]

The [[Monogamy in animals#Testis size|relative size of the testes]] is often influenced by [[mating system]]s.<ref name="Pitcher, Dunn, Whittingham, 2005">{{cite journal | last1 = Pitcher | first1 = T.E. | last2 = Dunn | first2 = P.O. | last3 = Whittingham | first3 = L.A. | year = 2005 | title = Sperm competition and the evolution of testes size in birds | journal = Journal of Evolutionary Biology | volume = 18 | issue = 3| pages = 557–567 | doi=10.1111/j.1420-9101.2004.00874.x| pmid = 15842485 | s2cid = 18331398 | doi-access = free }}</ref> Testicular size as a proportion of body weight varies widely. In the mammalian kingdom, there is a tendency for testicular size to correspond with multiple mates (e.g., harems, [[polygamy]]). Production of testicular output sperm and spermatic fluid is also larger in polygamous animals, possibly a [[Sperm competition|spermatogenic competition]] for survival. The testes of the [[right whale]] are likely to be the largest of any animal, each weighing around 500&nbsp;kg (1,100&nbsp;lb).<ref>{{cite web |url=http://animaldiversity.ummz.umich.edu/site/accounts/information/Eubalaena_glacialis.html |author=Crane, J. |author2=Scott, R. |year=2002 |title=Eubalaena glacialis |work=Animal Diversity Web |access-date=1 May 2009 |archive-date=28 March 2022 |archive-url=https://web.archive.org/web/20220328231412/https://animaldiversity.org/site/accounts/information/Eubalaena_glacialis.html |url-status=live }}</ref>

Among the [[Hominidae]], [[gorilla]]s have little [[female promiscuity]] and sperm competition and the testes are small compared to body weight (0.03%). [[Chimpanzee]]s have high promiscuity and large testes compared to body weight (0.3%). Human testicular size falls between these extremes (0.08%).<ref name=Shackelford>{{Cite journal | last1 = Shackelford | first1 = T. K. | last2 = Goetz | first2 = A. T. | doi = 10.1111/j.1467-8721.2007.00473.x | title = Adaptation to Sperm Competition in Humans | journal = Current Directions in Psychological Science | volume = 16 | pages = 47–50 | year = 2007 | s2cid = 6179167 }}</ref>

Testis weight also varies in seasonal breeders like [[red fox]]es,<ref name="s537">{{Harvard citation no brackets|Heptner|Naumov|1998|p=537}}</ref> [[golden jackal]]s,<ref name="h154">{{Harvard citation no brackets|Heptner|Naumov|1998|pp=154–155}}</ref> and [[coyote]]s.<ref name="Johnson2012"/>