\[ **BT: [[life#reproductive systems of vertebrates|reproductive systems in vertebrates]]** ] --- # the oestrous cycle Most females, in *most* species, only exhibit [[life#sexual motivation|sexual motivation]] when [[life#fertilisation|fertilisation]] is possible. --- ## terminology ### oestrous cycle: etymology and pronounciation [[The nominative form is ‘oestrus’; the adjectival form is ‘oestrous’. For example—the animal was in ‘oestrus’; the species has an ‘oestrous’ cycle.]][^1] [[The word ‘oestrus’ came from the Greek οἶστρος (lit. ‘gadfly’), via the Latin, where it came to mean any kind of frenzy or strong desire.]][^2] [[The pronunciation of ‘oestrus’ uses a a long e, as in thief. (The short e is the American pronunciation.)]][^3] ### alternate terminology [[Alternative oestrus terminology has been available for decades via Beach’s 1976 schema—vis-à-vis female sexuality—of (1) attractivity (i.e. sexual attractiveness), (2) proceptivity, and (3) receptivity.]][^4] [[In Beach’s 1976 schema, ‘sexual attractiveness’ includes non-behavioural clues such as genital appearance and odours.]][^5] [[In Beach’s 1976 schema, ‘proceptivity’ is the display of female behavioural patterns that are intended to initiate or maintain sexual interactions.]][^6] [[In Beach’s 1976 schema, ‘receptivity’ is female willingness to accept the male and allow copulation.]][^7] --- ## oestrous cycle stages [[The oestrous cycle has four phases. (1) pro-oestrus, (2) oestrus, (3) metoestrus, and (4) dioestrus.]][^8] ### pro-oestrus The follicular stage. ### oestrus Also known as the ‘heat’ (i.e. ‘being in heat’, ‘being in oestrus’. The female becomes sexually receptive to male advances—and also more sexually attractive to the male. [[Oestrus is a period of strong sexual drive in the female ovulatory cycle, during which the female accepts male copulation.]][^9] [[Despite the intensification of copulation during the ovulatory phase of their cycle, many primates allow males to copulation during other times as well; this has led to a belief that primates do not experience oestrus.]][^10] ### meoestrus Luteal phase. ### dioestrus [[Dioestrus is the period of (reproductive) inactivity between periods of oestrus (heats) in those animals with multiple oestrous cycles in a given breeding season.]][^11] --- ## types of breeding cycles ### mono-oestrus [[Larger mammals tend to have a single annual breeding season (with males sharing a similar cycle of sexual activity).]][^12] ### polyoestrus [[Some species are polyoestrus, with many breeding cycles in a year; the males may be sexually active the entire time.]][^13] ### spontaneous vs. induced ovulation In some species, ovulation occurs **spontaneously** (in response to hormones); in others, it is **induced** (by mating: this is ‘reflex ovulation’).[^14] --- ## the oestrus cycle in specific species ### the oestrus cycle in primates > ‘In female mammals (other than most **Primates**, *Compare* **Menstrual cycle**) the hormonally controlled, regularly repeated stages by which the body is prepared for reproduction. In anoestrus the female reproductive apparatus is inactive; in pro-oestrus it becomes active; and in oestrus ovulation usually occurs (in some species ovulation is triggered by copulation) and the female becomes receptive to males. Unless fertilization occurs, oestrus gives way to anoestrus as the cycle repeats.’[^15] ## endnotes [^1]: George W. Corner, ‘[[Corner, ‘Etymology and Pronunciation of the Word “Oestrus” and Its Derivatives’, 1937|Etymology and Pronunciation of the Word “Oestrus” and Its Derivatives]]’, *Science*, vol. 58, no. 2199 (1937), p. 197, https://doi.org/10.1126/science.85.2199.197; M. A. Hill, ‘[[Hill, ‘Estrous Cycle’, 2019|Estrous Cycle]]’, *Embryology*, UNSW Embryology, last modified 24 December 2019, 11:39, https://embryology.med.unsw.edu.au/embryology/index.php/Estrous_Cycle. [^2]: George W. Corner, ‘[[Corner, ‘Etymology and Pronunciation of the Word “Oestrus” and Its Derivatives’, 1937|Etymology and Pronunciation of the Word “Oestrus” and Its Derivatives]]’, *Science*, vol. 58, no. 2199 (1937), p. 197, https://doi.org/10.1126/science.85.2199.197. [^3]: George W. Corner, ‘[[Corner, ‘Etymology and Pronunciation of the Word “Oestrus” and Its Derivatives’, 1937|Etymology and Pronunciation of the Word “Oestrus” and Its Derivatives]]’, *Science*, vol. 58, no. 2199 (1937), p. 197, https://doi.org/10.1126/science.85.2199.197. [^4]: Alan F. Dixon, *[[Dixon, Primate Sexuality, 1998|Primate Sexuality: Comparative Studies of the Prosimians, Monkeys, Apes, and Human Beings]]* (Oxford University Press, 1998, p. 94). [^5]: Alan F. Dixon, *[[Dixon, Primate Sexuality, 1998|Primate Sexuality: Comparative Studies of the Prosimians, Monkeys, Apes, and Human Beings]]* (Oxford University Press, 1998, p. 94). [^6]: Alan F. Dixon, *[[Dixon, Primate Sexuality, 1998|Primate Sexuality: Comparative Studies of the Prosimians, Monkeys, Apes, and Human Beings]]* (Oxford University Press, 1998, p. 94). [^7]: Alan F. Dixon, *[[Dixon, Primate Sexuality, 1998|Primate Sexuality: Comparative Studies of the Prosimians, Monkeys, Apes, and Human Beings]]* (Oxford University Press, 1998, p. 94). [^8]: Elizabeth Martin and Robert Hine, ‘oestrus cycle (sexual cycle), in *A Dictionary of Biology*, 6th ed. (Oxford University Press, 2008), [https://www.oxfordreference.com/display/10.1093/acref/9780199204625.001.0001/acref-9780199204625-e-3058](https://www.oxfordreference.com/display/10.1093/acref/9780199204625.001.0001/acref-9780199204625-e-3058). [^9]: Bogusław Pawłowski, ‘[[Pawłowski, ‘Loss of Oestrus and Concealed Ovulation in Human Evolution’, 1999|Loss of Oestrus and Concealed Ovulation in Human Evolution: The Case against the Sexual-Selection Hypothesis]]’, *Current Anthropology*, vol. 40, no. 3 (1999), p. 258, <https://doi.org/10.1086/200017>. [^10]: Bogusław Pawłowski, ‘[[Pawłowski, ‘Loss of Oestrus and Concealed Ovulation in Human Evolution’, 1999|Loss of Oestrus and Concealed Ovulation in Human Evolution: The Case against the Sexual-Selection Hypothesis]]’, *Current Anthropology*, vol. 40, no. 3 (1999), p. 258, <https://doi.org/10.1086/200017>. [^11]: ‘Dioestrus’, *Collins English Dictionary*, 2012 digital edition, accessed 14 March 2025, https://www.dictionary.com/browse/dioestrus; Elizabeth Martin and Robert Hine, ‘Oestrus Cycle (Sexual Cycle)’, in *A Dictionary of Biology*, 6th ed. (Oxford University Press, 2008), [https://www.oxfordreference.com/display/10.1093/acref/9780199204625.001.0001/acref-9780199204625-e-3058](https://www.oxfordreference.com/display/10.1093/acref/9780199204625.001.0001/acref-9780199204625-e-3058). [^12]: Elizabeth Martin and Robert Hine, ‘oestrus cycle (sexual cycle), in *A Dictionary of Biology*, 6th ed. (Oxford University Press, 2008), [https://www.oxfordreference.com/display/10.1093/acref/9780199204625.001.0001/acref-9780199204625-e-3058](https://www.oxfordreference.com/display/10.1093/acref/9780199204625.001.0001/acref-9780199204625-e-3058); D. C. D. Happold, ed., *[[Happold, Mammals of Africa (vol. 3), 2013|Mammals of Africa. Volume 3: Rodents, Hares and Rabbits]]* (Bloomsbury 2013), p. 727. [^13]: Elizabeth Martin and Robert Hine, ‘oestrus cycle (sexual cycle), in *A Dictionary of Biology*, 6th ed. (Oxford University Press, 2008), [https://www.oxfordreference.com/display/10.1093/acref/9780199204625.001.0001/acref-9780199204625-e-3058](https://www.oxfordreference.com/display/10.1093/acref/9780199204625.001.0001/acref-9780199204625-e-3058). [^14]: Jennifer Denver, *[[Denver, Female Biology, 2024|Female Biology]]* (University of San Francisco, 2024), p. 223. https://repository.usfca.edu/faculty_books_all/108. [^15]: Michael Allaby, ed., ‘Oestrus cycle (estrus cycle)’, *A Dictionary of Zoology*, 5th edition (Oxford University Press, 2020), http://dx.doi.org/10.1093/acref/9780198845089.001.0001.