Strangest Genitals In The Animal Kingdom

Geoff Gallice, via Wikimedia Commons

Here at IFLS, we love many things. But we relish the opportunity to talk about two of our favorite subjects- animals, and genitals. So we thought we would dedicate an entire article on wacky willies and quirky nether regions. Because who doesn’t love to learn about four headed penises and musical privates? You can thank us afterwards for this enlightening genital journey.

“Singing” Genitals

Who wants a musical penis?! Don’t lie, of course you do. Water boatmen (Micronecta scholtzi) are tiny freshwater insects that you’ll find throughout Europe. They might not look like much, but they’re actually the loudest animal relative to body size. They can create noises of up to 99 decibels, which is roughly equivalent to listening to an orchestra from the front row. How do they do it? With their penises, of course. Similar to how a cricket will produce sound by rubbing body parts together, water boatmen rub their penis along their ribbed abdomen, kind of like a Guiro, only much more amusing. This is called stridulation.

Image credit: BBC Nature

Four Headed Penises?!

Like the platypus, echidnas are monotremes, or egg-laying mammals. There are four extant species of echidna that you can find in New Guinea and Australia. Alongside looking like a platypus/hedgehog hybrid, echidnas have various other odd features. Their tongues are extremely long, reaching around 7 inches in length. And then there’s the penis. Their penises actually have four heads. Yes, you read that correctly. If it’s any consolation, only one is active at a time; they actually rotate (in the line of duty, not physically like an exorcist penis), because obviously we don’t want one getting all the action. But it doesn’t end there. Females will mate with lots of males, and to ensure the best chance of reproductive success the sperm bundle together like a comet in order to swim more efficiently. Super sperm.

Image credit: Gordon Grigg, University of Queensland


There isn’t a great deal to say about the genitals of the elasmobranchs (sharks, rays and skates), except just to point out that they have a pointy double penis. These reproductive organs, called claspers, are used to deposit sperm into the female’s cloaca. This would perhaps be a good time to mention that cloacas are equally weird- they are the singular opening found in some animals that are used for urination, mating and defecation. Nice.

Image credit: Jean-Lou Justine, via Wikimedia Commons

Willy Wars

Good sir, I challenge you to a dual of… Penis cuffs? Hmm… Flatworms are hermaphrodites, meaning that they have both male and female reproductive organs. Producing eggs is more costly than producing sperm, so when two flatworms come together to mate they fight over who gets to wear the trousers in the relationship. During the penis crusade, the flatworms will fence, sometimes quite violently, in an attempt to impregnate the other without getting pregnant themselves.

Image credit: Yeowatzup, via Wikimedia Commons


Snakes and lizards, which are collectively known as squamates, have some rather funky genitals. Their male sexual organ is called a hemipenis; individual males have two hemipenes which they alternate between when mating with females. Some are even embellished with sharp spines to stop the male from slipping out of the female’s cloaca. Lovely.

Rattlesnake hemipenis. Image credit: Tess Thornton, via Wikimedia Commons.

Giant Genitals

Relative to their body size, barnacles have the largest penises in the animal kingdom; they can be up to 40 times the length of their body. I think that would be a tad difficult to tuck away if that were the case for humans. Barnacles are sessile organisms, i.e. fixed and immobile. They are therefore equipped with these giant genitals in order to seek out females that could be some distance away. Some other sessile organisms have evolved a slightly different approach by just shooting their load into the environment so the sperm may cross paths with an egg.

Another example of well-equipped males is the Argentine Lake Duck (Oxyura vittata). A report back in 2011 in Nature described this animal as having the longest bird penis on record, reaching a whopping 42.5 centimeters. Most birds don’t actually have penises and they instead mate by touching openings. This finding was therefore a bit of a surprise, and scientists aren’t entirely sure as to why it is quite so long. Some speculate that the brush-like tip of the penis may serve to remove sperm from other males that has already been deposited in the female’s cloaca.

Image Credit: K McCracken/ Nature

Detachable Penises

Argonauts, which are a type of octopus, don’t bother getting cozy and cuddly with their mates during the deed since they pack their sperm into a detachable tentacle called a hectocotylus. This then goes on its merry way and swims into the female to fertilize her. Females can actually store several of these from different males so that she can become fertilized more than once over a period of a few days. No post-coitus snuggles for Argonauts, then.


So I’ve had enough talk of actual penises for one day, sorry. It’s time for females to be in the spotlight. Female hyenas produce a lot of testosterone, meaning that they develop pseudo-penises. These are actually just enlarged clitorises, but they can reach up to 7 inches long! The poor hyenas actually have to give birth through these appendages, and unfortunately a lot of the offspring die of suffocation during the process. Copulation is also tricky business since the male has to somehow get his penis inside her lady penis. Sounds… Interesting…

Swapping Genitals

Earlier this year, a report in Current Biology described insects of the newly discovered genus Neotrogla which have apparently swapped genitals. The female dons a large, penis-like appendage called a gynosome which is inserted into the male’s opening. The gynosomes are adorned with spines so that the male can’t get away, and copulation can last between 40 and 70 hours! Wow.


Do you know of any more examples of extremely bizarre genitals? List them in the comments!


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