Sex Differences in Play Fighting Revisited: Traditional and Nontraditional Mechanisms of Sexual Differentiation in Rats
Abstract
In the traditional model for sexual differentiation in mammals, the female phenotype is the default condition. That is, the female-typical pattern will persist unless acted upon by hormones early in development. The frequency of play fighting in rats, as in most other mammals, is sexually differentiated, and conforms to the traditional model. Males engage in more play fighting than females, and this can be reduced to female-typical levels by neonatal castration. Furthermore, females can be induced to play fight at male-typical levels if treated with testosterone neonatally. Fractionation of play fighting into its constituent components, attack and defense, reveals that it is the frequency of attack that is sexually differentiated, not the likelihood of defense. However, in males, defensive behavior changes at puberty so that the play becomes "rougher." For males to switch to this rougher form of play fighting, they have to be androgenized perinatally. Hence, for males, this second aspect of play fighting that is sexually differentiated also follows the traditional model. In marked contrast, development of the female-typical pattern does not. Neonatal treatment of females with testosterone has no effect; at puberty, they still show the female-typical pattern. On the the other hand, ovariectomy, either at birth or at weaning, leads to females exhibiting the male-typical transition to rougher play fighting at puberty. That is, ovarian hormones appear to actively inhibit the expr…
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The sex difference in play frequency likely arises from early life hormone-induced changes in the development of relevant brain mechanisms.
“This sex difference likely arises from early life hormone‐induced changes in the development of relevant brain mechanisms (see Pellis 2002 for a review).”
From Partner Choice and Context‐Dependent Sex Differences in Rat Rough‐and‐Tumble Play (2026) · cites this paper as Pellis 2002
With the onset of puberty, the frequency of play fighting declines in rats.
“With the onset of puberty, however, the frequency of play fighting declines (Pellis & Pellis, 1990, 1991;Pellis, 2002;Pellis et al., 1997;Thor & Holloway, 1984).”
From Play fighting in androgen-insensitivetfm rats: Evidence that androgen receptors are necessary for the development of adult playful attack and defense (2006) · cites this paper as Pellis, 2002
The sex difference in the frequency of play (females playing more than males) is contrary to that typically reported in many other studies.
“With regard to the sex difference in the frequency of play, this finding is contrary to that typically reported in many other studies (Pellis, 2002;Pellis et al., 1997;Thor & Holloway, 1986).”
From Play fighting in androgen-insensitivetfm rats: Evidence that androgen receptors are necessary for the development of adult playful attack and defense (2006) · cites this paper as Pellis, 2002
Male and female rats differ in the frequency and pattern of play fighting as juveniles.
“Not only do male and female rats differ in the frequency and pattern of play fighting as juveniles”
From Play fighting in androgen-insensitivetfm rats: Evidence that androgen receptors are necessary for the development of adult playful attack and defense (2006) · cites this paper as Pellis, 2002
Play fighting in rats is a complex behavior comprising many dissociable components.
“As already noted, play fighting in rats is a complex behavior comprising many dissociable components”
From Play fighting in androgen-insensitivetfm rats: Evidence that androgen receptors are necessary for the development of adult playful attack and defense (2006) · cites this paper as Pellis, 2002
As adults both sexes reduce the frequency of playful attack, but tend to switch to different tactics of defense.
“As adults both sexes reduce the frequency of playful attack, but tend to switch to different tactics of defense (Pellis, 2002).”
From Play fighting in androgen-insensitivetfm rats: Evidence that androgen receptors are necessary for the development of adult playful attack and defense (2006) · cites this paper as Pellis, 2002
To produce the fully male-typical pattern of play requires both masculinization and defeminization.
“to produce the fully male-typical pattern of play requires both masculinization and defeminization (Pellis, 2002).”
From Play fighting in androgen-insensitivetfm rats: Evidence that androgen receptors are necessary for the development of adult playful attack and defense (2006) · cites this paper as Pellis, 2002
In early adulthood, male rats are more likely to use defensive tactics that make their rough-and-tumble play seem rougher.
“in early adulthood are more likely to use defensive tactics that makes their RTP seem rougher (Pellis, 2002).”
From The rough-and-tumble play of rats as a natural behavior suitable for studying the social brain (2022) · cites this paper as Pellis, 2002
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“For example, under some rearing and testing conditions, males initiate more nape attacks (Thor and Holloway, 1984), and in early adulthood are more likely to use defensive tactics that makes their RTP seem rougher (Pellis, 2002).”
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“This sex difference likely arises from early life hormone-induced changes in the development of relevant brain mechanisms (see Pellis 2002 for a review).”
Self-citation
- Authors
- Pellis, S. M.
- Affiliations
- University of Lethbridge (CA)
- Corresponding author
- Pellis, Sergio M.
- ORCID
- Pellis, Sergio M.
- Venue
- Archives of Sexual Behavior
- Published
- 2002-02
- Volume
- 31
- Issue
- 1
- Pages
- 17-26
- ISSN
- 0004-0002 (ISSN-L)
- 1573-2800
- OpenAlex
- W319684598
- Cited by
- 124
- References
- 6
- Citations by year
- 2026: 3 · 2025: 4 · 2024: 4 · 2023: 4 · 2022: 3 · 2021: 4 · 2020: 2 · 2019: 3 · 2018: 4 · 2017: 8 · 2016: 9 · 2015: 11 · 2014: 4 · 2013: 3 · 2012: 2
- FWCI
- 2.53
- Type
- journal article
- Language
- en
- Open access
- closed
- Licence
- Locations
- Archives of Sexual Behavior (publishedVersion)
- PubMed (publishedVersion)
- Funders
- Natural Sciences and Engineering Research Council of Canada
- Topics
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Sexual Differentiation and Disorders
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Genetic and Clinical Aspects of Sex Determination and Chromosomal Abnormalities
- Social Sciences › Psychology › Social Psychology › Neuroendocrine regulation and behavior
- Keywords
- play fighting, sexual differentiation, sex differences, rats, neonatal testosterone, neonatal castration, ovarian hormones, ovariectomy, puberty, androgenization
- MeSH terms
- Animals, Behavior, Animal, Competitive Behavior, Female, Male, Ovary, Play and Playthings, Sex Factors, Testosterone, Rats
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