In some research papers, transsexuality is correlated with measurable differences in brain structure. For example:

  • Zhou et al. (1995) inspected the central subdivision of the bed nucleus of the stria terminalis (BSTc), and found female-sized BSTc's in male-to-female transsexuals.
  • Berglund et al. (2008) found female-like hypothalamus activation in male-to-female transsexuals in response to smelling odorous steroids.

If there is a neurobiological basis for transsexuality, it seems reasonable to expect to see transsexuality in non-human animals. This leads me to my question:

Has transsexuality been observed in animals other than humans, and how was it observed?


  • Zhou et al., A sex difference in the human brain and its relation to transsexuality, Nature 378 (1995), 68-70.
  • Berglund et al., Male-to-Female Transsexuals Show Sex-Atypical Hypothalamus Activation When Smelling Odorous Steroids, Cereb. Cortex 18 (2008), 1900-1908.

1 Answer 1


Transexuality is a very social (and human) phenomena that's directly a consequence of how we define it as a society and indirectly a consequence of having distinct male/female ideologies.

Humans can be born as an ambiguous sex. We have a wide spectrum of hermaphrodites from androgen insensitivity syndrom (i.e. genetically "male" but can be legally "female" and can have varying degrees of both sex organs). So our definitions of male/female aren't exactly robust in the first place.

Most (probably all) animals do not have language and are unlikely to have social symbols that are meaningful to them. Most plants can change sex under stress, oysters can, too. Many organisms don't have a defined sex role (all of them are hermaphrodites). C. elegans are mostly hermaphrodites but can have the rare male. Often, the gender changes here are a direct biological response, rather than a social response, whereas with humans, it's more about responding to a social label.

There's some small chance that some other species have developed some sort of social sex expectations (I.e., gender) and have somehow had members challenge it, but it would be really hard to tell without sharing brain architecture, facial expressions, or language with them.

  • 3
    $\begingroup$ In your second paragraph, do you mean 'sex' instead of 'gender'? I feel like this is an important distinction to keep track of for this sort of question. $\endgroup$ Jul 8, 2013 at 8:07
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    $\begingroup$ yes you're right, edited. $\endgroup$ Jul 8, 2013 at 12:23
  • $\begingroup$ Any new findings in the last 10 years? I assume the most likely place to find evidence of non-human transgenderism would be in other apes, particularly chimpanzees. 1) They are more like us genetically and may therefore share whatever biological causes there may be. 2) They are also highly social creatures who have culture, form societies, and have distinct gender roles which can differ between groups based on their unique culture and circumstances. For example, in a documentary I saw about chimps, there was what could have been a gender-non-conforming male who associated mostly with females. $\endgroup$
    – ibonyun
    Aug 10, 2023 at 18:43

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