View source for Lordosis behavior

{{Short description|Body posture in mammals for sexual receptivity}}
{{about|the animal sexual posture|the human spinal shape and disorders thereof|Lordosis}}
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| image1 = Cats having sex in Israel.jpg
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| footer = Lordosis behavior seen in different mammals. Clockwise from top left: [[cat]]s, [[hamster]]s, [[elephant]]s, and [[eastern gray squirrel]]s.
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'''Lordosis behavior''' ({{IPAc-en|l|ɔːr|ˈ|d|oʊ|s|ɪ|s}}<ref name="American Heritage Dictionary - lordosis"/>), also known as '''mammalian lordosis''' (Greek lordōsis, from ''lordos'' "bent backward"<ref name="American Heritage Dictionary - lordosis">{{cite web|url=https://ahdictionary.com/word/search.html?q=lordosis|publisher=The American Heritage Dictionary|title=lordosis|access-date=January 3, 2017|archive-url=https://web.archive.org/web/20170104090839/https://ahdictionary.com/word/search.html?q=lordosis|archive-date=January 4, 2017|url-status=dead}}</ref>) or '''presenting''', is the naturally occurring body posture for sexual receptivity to [[Copulation (zoology)|copulation]] present in females of most [[mammal]]s including [[rodents]], [[elephants]], and [[Felidae|cats]]. The primary characteristics of the behavior are a lowering of the forelimbs but with the rear limbs extended and [[hip]]s raised, [[ventral]] arching of the [[Vertebral column|spine]] and a raising, or sideward displacement, of the [[tail]]. During lordosis, the spine curves [[dorsoventral]]ly so that its apex points towards the abdomen.

==Description==
Lordosis is a reflex action that causes many non-primate female mammals to adopt a body position that is often crucial to reproductive behavior. The posture moves the [[pelvic tilt]] in an anterior direction, with the posterior pelvis rising up, the bottom angling backward and the front angling downward. Lordosis aids in copulation as it elevates the hips, thereby facilitating penetration by the [[penis]]. It is commonly seen in female mammals during [[estrus]] (being "in heat"). Lordosis occurs during copulation itself and in some species, like the cat, during pre-[[animal sexual behavior|copulatory]] behavior.<ref>{{cite web |title=Female Cat in Heat |url=http://www.pet-informed-veterinary-advice-online.com/cat-in-heat.html#lordosis-heat |website=Pet Informed |access-date=14 November 2020}}</ref>

==Neurobiology==

The lordosis [[reflex arc]] is hardwired in the spinal cord, at the level of the lumbar and sacral [[Vertebra (anatomy)|vertebrae]] (L1, L2, L5, L6 and S1).<ref name="pfaff1994">Pfaff D. W. , Schwartz-Giblin S., Maccarthy M. M., Kow L-M (1994). "Cellular and molecular mechanisms of female reproductive behaviors", in Knobil E., Neill J. D. ''The physiology of reproduction'', Raven Press, 2nd edition.</ref> In the brain, several regions modulate the lordosis reflex. The [[vestibular nuclei]] and the [[cerebellum]], via the vestibular tract, send information which makes it possible to coordinate the lordosis reflex with [[Equilibrioception|postural balance]]. More importantly, the ventromedial [[hypothalamus]] sends projections that inhibit the reflex at the spinal level, so it is not activated at all times.<ref name="Kow2007">{{cite journal | author = Kow L.M.|author2=Florea C.|author3=Schwanzel-Fukuda M.|author4=Devidze N.|author5=Kami K.H.|author6=Lee A.|author7=Zhou J.|author8=Maclaughlin D.|author9=Donahoe P.|author10=Pfaff D. | title = Development of a Sexually Differentiated Behavior and Its Underlying CNS Arousal Functions | year = 2007 | journal = Curr. Top. Dev. Biol. | volume = 79 | pages = 37–59 | doi = 10.1016/S0070-2153(06)79002-0 | pmid = 17498546 | series = Current Topics in Developmental Biology | isbn = 9780123739131 }}</ref> Sex hormones control reproduction and coordinate sexual activity with the physiological state. Schematically, at the [[breeding season]], and when an [[ovum]] is available, hormones (especially [[estrogen]]) simultaneously induce [[ovulation]] and [[estrus]] (heat). Under the action of estrogen in the hypothalamus, the lordosis reflex is uninhibited.<ref name="flanagan">{{cite journal | author = Flanagan-Cato L.M. | year = 2011 | title = Sex differences in the neural circuit that mediates female sexual receptivity | journal = Frontiers in Neuroendocrinology | volume = 32 | issue = 2| pages = 124–136 | pmc=3085563 | pmid=21338620 | doi=10.1016/j.yfrne.2011.02.008}}</ref> The female is ready for copulation and [[fertilization]].

When a male mammal mounts the female, tactile stimuli on the flanks, the [[perineum]] and the [[Rump (animal)|rump]] of the female are transmitted via the [[sensory nerve]]s in the [[spinal cord]]. In the spinal cord and lower [[brainstem]], they are integrated with the information coming from the brain, and then, in general, a [[Action potential|nerve impulse]] is transmitted to the [[muscle]]s via the [[motor nerve]]s. The contraction of the longissimus and transverso-spinalis muscles causes the ventral arching of the vertebral column.<ref name="pfaff1994"/>

== Hormonal and cerebral regulation ==
Sexual behaviour is optimized for reproduction, and the [[hypothalamus]] is the key brain area which regulates and coordinates the physiological and behavioural aspects of reproduction.<ref name="Plant">Plant T., Zeleznik A. (Eds). ''[https://books.google.com/books?id=I1ACBAAAQBAJ Knobil and Neill's Physiology of Reproduction]''. Academic Press, 4th edition, 2015</ref> Most of the time, the [[ventromedial nucleus]] of the hypothalamus (VMN) inhibits lordosis. But when environmental conditions are favorable and the female is in estrus, the [[estrogen]] [[hormone]], [[estradiol]], induces [[sexual receptivity]] by the [[neuron]]s in the [[ventromedial nucleus]],<ref name="pmid9638959">{{cite journal |vauthors=Kow LM, Pfaff DW |title=Mapping of neural and signal transduction pathways for lordosis in the search for estrogen actions on the central nervous system |journal=Behav. Brain Res. |volume=92 |issue=2 |pages=169–180 |date=May 1998 |pmid=9638959 |doi=10.1016/S0166-4328(97)00189-7|s2cid=28276218 }}</ref> the [[periaqueductal gray]], and other areas of the [[brain]]. The ventromedial hypothalamus sends impulses down [[axon]]s synapsing with neurons in the periaqueductal gray. These convey an impulse to neurons in the medullary [[reticular formation]] which project down the [[reticulospinal tract]] and synapse with the neurobiological circuits of the lordosis reflex in the [[spinal cord]] (L1–L6). These neurobiological processes induced by estradiol enable the tactile stimuli to trigger lordosis.

The mechanisms of regulation of this [[Estrogen-dependent condition|estrogen-dependent]] lordosis reflex have been identified through different types of [[experiment]]s. When the VMN is lesioned lordosis is abolished; this suggests the importance of this cerebral structure in the regulation of lordosis. Concerning hormones, displays of lordosis can be affected by ovariectomy, injections of estradiol benzoate and progesterone,<ref>{{cite journal|title=Development of steroid-induced lordosis in female guinea pigs: effects of different estradiol and progesterone treatments, clonidine, and early weaning.|author1=Olster, D.H. |author2=Blaustein, J.D.|journal=Hormones and Behavior |year=1989|volume=23|issue=1|pages=118–129|pmid=2538389|doi=10.1016/0018-506x(89)90079-2|s2cid=26078948 }}</ref> or exposure to [[Stress (biology)|stress]] during puberty.<ref name="auto">{{cite journal|author1=Jasmina Kercmar |author2=Stuart Tobet |author3=Gregor Majdic |title=Social Isolation during Puberty Affects Female Sexual Behavior in Mice  |journal=Frontiers in Behavioral Neuroscience|year=2014 |doi=10.3389/fnbeh.2014.00337 |pmid=25324747 |volume=8 |pages=337 |pmc=4179611|doi-access=free }}</ref><ref>{{cite journal|author1=D. Daniels |author2=LM. Flanagan-Cato |title=Social Isolation during Puberty Affects Female Sexual Behavior in Mice |journal=Journal of Neurobiology|year=2000|pmid=10992252|volume=45|issue=1 |pages=1–13|doi=10.1002/1097-4695(200010)45:1<1::AID-NEU1>3.0.CO;2-W }}</ref> Specifically, stress can suppress the [[Hypothalamic–pituitary–gonadal axis|hypothalamic-pituitary-gonadal (HPG) axis]] and therefore decrease concentrations of gonadal hormones. Consequently, these reductions in exposure to gonadal hormones around puberty can result in decreases in sexual behavior in adulthood, including displays of lordosis.<ref name="auto" />

== In humans==
While lordosis behavior has not been observed in humans, positions similar to lordosis can be seen in those being [[Doggy style|mounted from behind]], with the autonomous lordosis reflex replaced by a conscious decision to expose the vulva for penetration.<ref name="Pfaus">Pfaus, J. G.; Flanagan-Cato, L. M.; Blaustein, J. D. "Female sexual behavior". in Plant T., Zeleznik A. (Eds). ''Knobil and Neill's Physiology of Reproduction''. Academic Press, 4th edition, 2015 (p. 2301)</ref>

In a 2017 study, using 3D models and eye-tracking technology it is shown that the slight thrusting out of a woman's hips influences how attractive others perceive her to be and captures the gaze of both men and women.<ref>{{cite web |url=https://www.springer.com/gp/about-springer/media/research-news/all-english-research-news/why-arched-backs-are-attractive/15163220|title=Why arched backs are attractive |author=Elizabeth Hawkins |date=October 25, 2017 |publisher=springer.com}}</ref> The authors argue "while reflexive lordosis posture is not exhibited by human females and receptivity is not passive or obligatory for them, a manifestation of lumbar curvature might serve as a vestigial remnant of proceptivity-/receptivity-communicative signal between men and women".<ref>{{cite journal |doi=10.1007/s40806-017-0123-7 |title=Arching the Back (Lumbar Curvature) as a Female Sexual Proceptivity Signal: an Eye-Tracking Study |year=2017 |last1=Pazhoohi |first1=F. |last2=Doyle |first2=J.F. |last3=Macedo |first3=A.F. |last4=Arantes |first4=J. |journal= Evolutionary Psychological Science |volume=4 |issue=2 |pages=1–8|s2cid=149046079 }}</ref> Previously, [[anthropologist]] [[Helen Fisher (anthropologist)|Helen Fisher]] also speculated that when a human female wears [[high-heeled footwear]] the buttocks thrusts out and the back arches into a pose that simulates lordosis behavior, which is why high heels are considered "sexy".<ref>{{cite web |url=https://www.today.com/news/do-high-heels-empower-or-oppress-women-wbna32970817|archive-url=https://web.archive.org/web/20090926083741/http://today.msnbc.msn.com/id/32970817/ns/today-today_fashion_and_beauty|archive-date=September 26, 2009|title=Do high heels empower or oppress women? |author=Laura T. Coffey |date=Sep 23, 2009 |publisher=TODAY|access-date=November 1, 2021}}</ref> Recent evidence has also supported the perception of sexual receptivity in women when arching the back in supine and quadruped poses.<ref>{{cite journal |doi=10.1007/s40750-023-00212-3 |title=Lordosis Posture (Arching the Back) Indicates Sexual Receptivity in Women |year=2023 |last1=Pazhoohi |first1=F. |last2=Garza |first2=R. |last3=Kingstone |first3=A.|journal= Adaptive Human Behavior and Physiology |volume=9 |issue=2 |pages=125–140 |s2cid=257540903 }}</ref><ref name=":0">{{cite journal |doi=10.3390/sexes3010005 |title=Sexual Receptivity Signal of Lordosis Posture and Intra-Sexual Competition in Women |year=2022 |last1=Pazhoohi |first1=F. |last2=Garza |first2=R. |last3=Kingstone |first3=A.|journal= Sexes |volume=3 |issue=1 |pages=59–67|doi-access=free |hdl=2429/81188 |hdl-access=free }}</ref> Researchers have found that women perceive other women exhibiting this posture as a potential threat to their romantic relationship.<ref name=":0" />

==See also==
*[[Ethogram]]
*[[Pelvic thrust]]

==References==
{{reflist}}

{{Sex (biology)}}
{{Animal sexual behavior}}

{{DEFAULTSORT:Lordosis Behavior}}
[[Category:Ethology]]
[[Category:Mammalian sexuality]]
[[Category:Physiology]]
[[Category:Sex positions]]
[[Category:Sexual intercourse]]
[[Category:Sex]]