7 Gender-Altering Animals

From the theater of ancient Greece to talent show TV, humans have a long and storied history of dressing up as the opposite sex.

But we’re not the only animal that’s good at gender alteration. We recently told you about female market squid who flash fake testes, probably to put the kibosh on unwanted male attention. Here are seven creatures who are great at pulling a sexual switcheroo.


Admit it: you alter your demeanor, a lot or a little, depending on who you’re with. Just about all of us do it. You’re just not as literal about it as a cuttlefish.

Male mourning cuttlefish actually show a different side of themselves depending on the company they’re with, especially if that company is mixed. A study out of Macquarie University in Sydney found that males can split themselves down the middle, appearing to be male on one side and female on the other. A male in between another male and a female will show his true male appearance to the female to flirt with her, while showing female colors to the male. That other male thinks he’s seeing two ladies (and no rival) and won’t realize that a budding romance is happening right in front of him.

Mr. Roper thinks something funny is going on here but has decided not to get involved.

Garter Snakes

Of all the animal romance rituals, the snake mating ball is certainly one of the most visually arresting, if not downright orgiastic-looking. Guaranteed to give the ophidiophobic a few nightmares, it’s also a squirmy stage for some clever sexual charades.

Red-sided garter snakes in a mating ball in Manitoba, Canada. Photograph by Norbert Rosing, National Geographic

In Manitoba, Canada, which has the highest concentration of garter snakes in the world, males emerge from hibernation slowly and groggily after eight months in the chilly ground. Pokey they may be, but they’re still on high alert for females to mate with. Some males, though, mimic female behavior at this time.

Researchers think that’s because females have a couple of survival advantages. When females emerge, they are quickly mobbed by male suitors, as are the female-mimicking “she-males.” The snakes at the center of mating balls are protected from predators (birds seek out the groggy males). Plus, all that transferred body heat allows the she-males to warm up more quickly and become fleeter of foot — well, maybe not foot– to avoid becoming lunch.

Snake in the grass? Perhaps. But one that lives to slither another day.

Spotted Hyena

It’s not just the males of the animal kingdom that adopt opposite sex traits. Female spotted hyenas are socially dominant, larger, and more aggressive than the males.

spotted hyenas picture
Spotted hyenas in Masai Mara National Reserve, Kenya. Frans Lanting, National Geographic

But it’s not only their behavior that’s masculine. Their clitoris is so enlarged it’s often referred to as a pseudo penis. It’s capable of erection, and the female has sex, urinates, and gives birth through it. Females also have a structure that looks remarkably like a scrotum. Even close up, it can be hard to distinguish a female from a male.

There are theories but no definitive reason for the female hyena’s pseudo penis.

“OMG, cool!” probably doesn’t count.

African Bat Bug

The African bat bug sucks the blood of bats (and sometimes bites humans). Cool enough, but even more intriguing, bat bugs have a serious game of strategy going on around their safety and sexual identity. Like bedbugs, bat bugs practice “traumatic insemination,” in which males stab females in the abdomen with needle-like penises and inject sperm directly into the bloodstream, which can harm the female. Males sometimes do this to each other as well.

To protect themselves, females developed paragenitals, a funnel-like genital opening that guides the penis to an area filled with immune cells. Males, then, developed their own version of these paragenitals. Then the females started imitating the more successful male imitations of the female paragenitals. (See pictures: “‘Torture’ Phalluses Give Beetles Breeding Boost.”)

Females imitating males imitating females sounds like it could get seriously confusing. It calls to mind Dr. Seuss’ Sneetches, who changed their appearance so often they couldn’t tell “which one was what one or what one was who.”

But it can’t be too perplexing: The bat bugs continue to reproduce.

Anemonefish, Parrotfish, and Hawkfish

Some animals don’t just appear to change genders—they actually turn into the opposite sex. Clown anemonefish all start out as male. If the female dies, the dominant male can change sex and become female. Another male will become the dominant male.

parrotfish picture
A stoplight parrotfish swims in Hol Chan Marine Reserve, Belize. Photograph by Brian Skerry, National Geographic

Parrotfish start out as male or female but have sex organs of both sexes; they are protogynous hermaphrodites, meaning they can change from female to male. Some females will become supermales: larger males with brilliant, lively coloring.

Hawkfish in the wild have been shown to be capable of “bi-directional” sex change, going from female to male and back again.

Kind of poetic that the ocean is home to such elegant gender fluidity.

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Liz Langley is the award-winning author of Crazy Little Thing: Why Love and Sex Drive Us Mad and has written for many publications including Salon, Details and the Huffington Post. Follow her on Twitter @LizLangley and at www.lizlangley.com
  • Kate B.

    Uhhhh sex and gender aren’t the same thing. Gender is something that humans have created; it is cultural and temporally variant. Animals do not have genders, so applying Western ideas of how men and women should behave is absurd.

  • Andy

    Kate, this isn’t sociology class where you can redefine words and ignore reality to suit your feelings. In the world of facts, gender is a synonym for sex, and animals do have genders. Acknowledging that males and females are different is not “applying Western ideas,” it’s a simple description of nature.

  • Behnam

    Hi everybody,
    I have a male Oscar fish whose mate have died few month ago and the male have been along in this period. This morning, I saw that he laid eggs ! Since I’m sure it is a male, whats the reason for this gender changing?

  • Behnam

    sorry, … have been alone…

  • Nate

    Andy, she actually isnt redefining words. Gender and sex are not synonymous, and this can be easily seen in any dictionary. Yes animals can change gender and sex, but to use the words inter-changeably like that is inaccurate. Gender is simply a number of traits more commonly aligned with one of the sexes, but it is not in essence the sex of the organism.

  • Ste Ríkhardsson

    You are wrong Andy. The other animals do not have genders. The word “gender” is from the French word “genre” which means “type, class, kind”.

    Gender is a psychological construct whereas sex is a physical entity. The word “gender” is used wrongly by most people as a synonym for sex mainly because for 99% of people in the world, the two are the same. But just because they are the same for you, it doesn’t mean it is the same for everyone.

    Even though there are two MAIN sexes, there are at least 16 types of sexes among humans. Many of these people are classed as “intersex”. Some people are born with XXY chromosomes or other combinations as well as ambiguous sex organs (sometimes totally ambiguous, sometimes with breasts and a penis, sometimes with a vagina, womb and flat chest, and sometimes with working or non-working sexual organs).

  • Robert T. Badger

    Kate B. Is that more politically correct yankee B……T I can smell.

  • edward

    eww this is the grosses thing I ever heard ewww animals are disgusting

  • Alex

    I hate how gender is a synonym for sex. It’s a different word in today’s language.
    And apparently it’s taboo to ask if someone means sex or identity.

  • Jonathan J.

    I agree with Andy. Anyone who genuinely believes that “sex and gender aren’t synonymous” or that “gender is a social construct” are those who thrive on attention but can’t deal with how the real world works.

  • Glen
  • Ionas

    @Behnam hope you see it. Some fishes change gender because of the environment. For example there are some fishes that change gender because of the temperature, or what is “available” at the moment. i mean if there are no females one female will become male and vice versa. check this article on wiki https://en.wikipedia.org/wiki/Polyphenism#Sex_determination

    As for the others gender IS a social construct. how women and men should act/react, be and what their role is in their society (work, cook etc) is a social construct. Having male genitals doesn’t necessarily make you a man. (Same for female genitals). Also there are a lot of people that have other than those 2 “types” of genitals as it was well admited by Ríkhardsson

  • Ángel

    Kate B., Nate, Ste Ríkhardsson, Alex, & Jonathan:

    You are all wrong in that gender identity is a human construct. It is a psychosocial construct, but it is not exclusive to humans simply because humans are not the only animals with a sense of culture and identity. This very article gave the example of an African Bat Bug, animals that have a sense of sexual identity, and they have typical gender roles. This is also common among reptiles, avian creatures, some aquatic mammals, and it obviously exists on humans. Some animals may not change their sexual features, but will still change their gender role for survival purposes. So, even though not all the transsexual animals mentioned are transgender, transgender animals exist because gender is a psychosocial construct based on cultures that does exist in non-humans.

  • Glory

    This is all natural in the animal kingdom. The animals and fish are not taking hormones and chemicals to alter their bodies or going to the surgeon to change their sex. Males are born with a penis, females are born with a vagina. Sometimes but rarely a person is born with both, in which case the DNA will tell the sex of the person, either XX or XY. Humans cannot change gender, they can only pay a surgeon to make fake sex organs, there is nothing natural about it. Secular humanism is rotting this nation and the brains of many. Repent and turn to the Lord Jesus Christ.

  • Jack Frost

    The religious (e.g. Glory) can be so sensitive/hateful when they cannot handle reality. This article was not about humans.

  • dudarino

    National Geographic should edit this, as a science-based publication/company–this misrepresents “gender” as the same as “sex,” and confuses the issue. (“Gender” reflects social or cultural aspects, while sex reflects biological aspects.)

    Please consider a correction.

  • Tyler

    There are many more examples of non-binary sex characteristics in the animal kingdom, like hermaphroditic snails that shoot sperm arrows into each others vaginas. Beyond animals, most plants and fungi are hermaphrodites. Also, most single-celled organisms reproduce asexually due to no gender, though at least one type of single-celled cilliate has 7 genders that can all mate with each other but not 2 of the same gender http://voices.nationalgeographic.org/2013/04/25/how-does-an-organism-get-seven-sexes/

    So really, most organisms on this planet do not conform to a binary gender system, but obviously from a biological perspective DNA recombination offers the best advantage for genetic diversity.

  • Paul

    Gender is not a psycho/social construct at all. This is largely feminist ideology that has found it’s way into institutions through gender studies and through the media into mainstream culture to question our gender roles which have been now defined as mere inventions. While the black and white idea of sex/gender is not what it was once believed it is still a reality and the norm for most people. We do however exist on a spectrum from male to female which take on many physiological traits and expressions. One is sexual attraction, one is hormonal, one is neuorchemical, and there are a few more. The idea is that the majority of people are traditional male and female by nature. There is another minority that dont fit neatly into these categories and share some attributes that are ‘borrowed’ from another sex. This could be homosexuality or having an outlook and interests that tend toward the opposite sex. There is an even smaller segment of society that blur the lines between gender/sex from their physicality to their behaviour, interests, hormones and brain chemistry. These people could be classified as transgender. They have always been around and always will be. Having acceptance and understanding would certainly help these people with any challenges they face but this does not mean that all gender is fluid. For the vast majority it isn’t. To exaggerate the actual number of people does a disservice to society and to science and to seeking truthful answers. The majority of society does have binary gender and following their defined natures allows them to be accepted and comfortable living in a society where the larger nature creates cultural stabillity and serving that stability provides the best least stressful and complicated environment for everyone. This idea of attempting to eradicate the idea of gender and gender roles flies in the face of science and nature for the MOST part, for MOST people. See, that’s my point, the other rarer forms exist but don’t be fooled by political agendas ( especially in academic science circles ) that there are no norms. There are norms and always will be no matter how much you exaggerate to attempt to gain political leverage for your belief systems. The deviation from the norm exists and always will. Acceptance and understanding is important but so are norms which are still the norm no matter what the discussion is and why.

  • Alison

    Thanks National Geographic- please keep posting items about transgender animals. The responses are best laugh I’ve had all day. Love to watch crazy men terrified of losing their “masculinity” and becoming a despised and inferior female. Don’t try to argue logically with these guys Kate, they’re hilariously crazy.

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