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.

garter snakes picture
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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  1. Jonathan J.
    September 22, 12:03 am

    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.

  2. Alex
    September 18, 10:25 pm

    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.

  3. edward
    August 5, 12:05 am

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

  4. Robert T. Badger
    Wombourne, England
    July 1, 6:39 pm

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

  5. Ste Ríkhardsson
    June 10, 5:20 am

    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).

  6. Nate
    United States
    February 3, 10:20 am

    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.

  7. Behnam
    February 2, 7:17 am

    sorry, … have been alone…

  8. Behnam
    February 2, 7:16 am

    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?

  9. Andy
    December 28, 2014, 12:34 am

    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.

  10. Kate B.
    United States
    June 30, 2014, 3:08 am

    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.