Editing Assortative mating (section)

== In non-human animals ==
[[File:Bufo japonicus formosus.jpg|thumb|right|240px|[[Japanese common toad]]]]
Assortative mating in animals has been observed with respect to body size and color. Size-related assortative mating is prevalent across many species of [[vertebrate]]s and [[invertebrate]]s.
It has been found in the simultaneous [[hermaphrodite]]s such as the [[land snail]] ''[[Bradybaena pellucida]]''. One reason for its occurrence can be reciprocal intromission (i.e. both individuals provide both male and female gametes during a single mating) that happens in this species. Therefore, individuals with similar body size pair up with one another to facilitate this exchange. Moreover, it is known that larger individuals in such hermaphroditic species produce more eggs, so mutual [[mate choice]] is another factor leading to assortative mating in this species.<ref>{{cite journal |last1=Kimura |first1=K. |last2=Hirano |first2=T. |last3=Chiba |first3=S. |year=2014 |title=Assortative mating with respect to size in the simultaneously hermaphroditic land snail Bradybaena pellucida |journal=Acta Ethologica |volume=18 |issue=3 |pages=265–268 |doi=10.1007/s10211-014-0211-7 |s2cid=13195409 }}</ref>

Evidence for size-related assortative mating has also been found in the mangrove snail, ''Littoraria ardouiniana'' and in the [[Japanese common toad]], ''Bufo japonicus''.<ref>{{cite journal | last1 = Ng | first1 = TPT | last2 = Williams | first2 = GA | year = 2014 | title = Size-dependent male mate preference and its association with size-assortative mating in a mangrove snail, littoraria ardouiniana | journal = Ethology International Journal of Behavioural Biology | volume = 120 | issue = 10| pages = 995–1002 | doi=10.1111/eth.12271| doi-access = free | bibcode = 2014Ethol.120..995N }}</ref><ref>{{cite journal | last1 = Hase | first1 = K | last2 = Shimada | first2 = M | year = 2014 | title = Female polyandry and size-assortative mating in isolated local populations of the Japanese common toad Bufo japonicus | journal = Biological Journal of the Linnean Society | volume = 113 | issue = 1| pages = 236–242 | doi=10.1111/bij.12339| doi-access = free }}</ref>

The second common type of assortative mating occurs with respect to coloration. This type of assortative mating is more common in socially monogamous bird species such as the [[eastern bluebird]]s (''Sialia sialis'') and [[western bluebird]]s (''Sialia mexicana''). In both species more brightly colored males mated with more brightly colored females and less brightly colored individuals paired with one another. Eastern bluebirds also mate assortatively for territorial aggression due to fierce competition for a limited number of nesting sites with tree swallows. Two highly aggressive individuals are better equipped to protect their nest, encouraging assortative mating between such individuals.<ref>{{cite journal | last1 = Harris | first1 = MR | last2 = Siefferman | first2 = L | year = 2014 | title = Interspecific competition influences fitness benefits of assortative mating for territorial aggression in Eastern Bluebirds (Sialia sialis) | journal = PLOS ONE | volume = 9 | issue = 2| page = e88688 | doi=10.1371/journal.pone.0088668 | pmid=24516672 | pmc=3916427| bibcode = 2014PLoSO...988668H | doi-access = free }}</ref>

Assortative mating with respect to two common color morphs: striped and unstriped also exists in a polymorphic population of eastern red-backed salamanders (''[[Plethodon cinereus]]'').<ref>{{cite journal |last1=Acord |first1=M. A. |last2=Anthony |first2=C. D. |last3=Hickerson |first3=C. A. M. |year=2013 |title=Assortative mating in a polymorphic salamander |journal=[[Copeia]] |volume=2013 |issue=4 |pages=676–683 |doi=10.1643/CE-13-003 |s2cid=56474427 }}</ref>

Assortative mating is also found in many socially monogamous species of birds. Monogamous species are often involved in bi-parental care of their offspring. Since males are equally invested in the offspring as the mother, both genders are expected to display mate choice, a phenomenon termed as mutual mate choice. Mutual mate choice occurs when both males and females are searching for a mate that will maximize their fitness. In birds, female and male ornamentation can indicate better overall condition or such individuals might have better genes, or be better suited as parents.<ref name=Jacobs/>