1 shaft, 4 heads: The echidna’s penis.

The echidna is an odd animal for many reasons. It looks like a cross between a hedgehog, a platypus and an anteater (and indeed it is commonly known as the “spiny anteater”). Additionally, the females of this mamalian species lay eggs, which is really rare – in fact, the only other mammal known to do this is the platypus (egg-laying mammals are called monotremes), so already we can see that these are special ickly cuties. But what is perhaps most bizarre about this little Australian waddler is its penis. Dare you look? GO ON SCROLL DOWN I DARES YE!

IT HAS FOUR HEADS! FOUR! I think it looks like the foot of a baby rhino or something. But be assured, it is in fact a penis. But WHY LAUREN?! I hear ye screech?! The short answer is that we don’t really know. What we do know that when a male echidna has sex with a female echidna, one side of the penis seems to shut down, leaving only two out of the four heads in use. The next time he mates, the heads on the other side will be used. In fact, if all four heads are active and grow in size, the penis would have great difficulty getting inside the reproductive tract of the female, which only has two canals.

I even found an academic paper on the echidna’s penis, published in one of America’s oldest academic journals nonetheless. Below is a direct quote from the article, describing how research on such matters is carried out (basically, it would seem, you train an animal to be okay with getting erections out of context, then you masturbate it until it ejaculates). YAY FOR SCIENCE!

In 2005, Currumbin Wildlife Sanctuary (Gold Coast,
Australia) came into possession of a 17-year-old captive
male echidna that had become habituated to human presence
as part of an interactive public display. Zookeepers
noted that, on handling, this animal would readily produce
an erection. Over a period of 2 weeks, zookeepers at Currumbin
Wildlife Sanctuary conditioned the echidna to develop
an erection to the point where it would ejaculate.
In preparation for semen collection, the echidna is placed
in lateral recumbency on a clean surface of the floor of
its enclosure. Using a closed fist, the zookeeper gently
pushes his hand into the lower abdomen of the animal,
at which time the echidna usually responds by pushing its
cloaca up against the zookeeper’s fist and developing an

What’s that you say, the imagery just isn’t strong enough? Well here is A VIDEO of the process! (You’re freakin’ welcome)

The scientists actually did some pretty cool research with the semen they collected. By examining the number of sperm in the ejaculate, they found that up to 100 individual sperm would bundle together, and this caused them to move very quickly in a very organised fashion- causing them to be much more effective working as a team than alone. What’ going on here? The most likely answer is sperm competition. Fertile females are never left alone for very long: Males will quite literally queue up to mate with them. With all this competition to be the one to fertilise the egg, males whose sperm behave in this “bundling” way will be more likely to father the offspring and therefore the team-building sperm would be favoured by natural selection, causing it to become widespread in the population.



Johnston, Steve D. and Smith, Brett and Pyne, Michael and Stenzel, Deborah J. and Holt, William V. (2007) One-Sided Ejaculation of Echidna Sperm Bundles.  The American Naturalist 170(6):E162-E164.

BoingBoing:  More than you maybe needed to know about the echidna

New Scientist: Exhibitionist spiny anteater reveals bizarre penis

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32 thoughts on “1 shaft, 4 heads: The echidna’s penis.

  1. DrBaka says:

    This was by far the most interesting and unexpected science post I’ve read today. Thanks!

  2. Greg Seal says:

    Super post, another example of bonkers biology.

  3. David Dempster says:

    ‘Only two canals’. LOL

    Those female echidnas are doing just fine!

  4. Lord Snooty says:

    Outstanding. In terms of sheer, out there, “God’s ‘avin’ a larf” unexpectedness, a penis with four heads ranks higher than a Higgs Boson. Is it me or is the little chap sporting a rather louche, Aussie grin in that photo? No matter, because science (plus your research) has, once again, been the highlight of my day. Many thanks, all the best, Snooty.

  5. Ian B says:

    Nature is so intriguing.

  6. […] Via PygmyLoris, who has also written about this amazing penis. His name is grumpy. Despite the penis, he's […]

  7. […] July 6: 1 shaft, 4 heads: The echidna’s penis.  This post is NSFW if you happen to work with a bunch of echidnas.  (post by @PygmyLoris, with a […]

  8. mayachic1 says:

    I never imagined that there were scientists whose job it was to manually stimulate an animals penis to the point of ejaculation. On some level I knew they existed, I just sort of blocked it out until now.

  9. […] or a coat of spines; others don’t. Snakes, lizards and kangaroos have two-pronged penises, while echidnas have four-pronged ones. Mammals inflate their penises with blood; birds use lymph; alligators have a permanently erect […]

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  11. Eddie Lopez says:

    An enchilada with a penis? Impossible. (puts glasses on) oh,
    echidnas. Never mind.

  12. ryan says:

    if only my penis was that big in comparison my body. oh and what a lucky animal whose only job is to sit around and get jacked off all day

  13. Paul Tallent says:

    clever post Ryan – laughing all night over your post……

  14. Knuckles Echidna says:

    Thats why Rouge loves me so much

  15. Gradivus says:

    There is some science that I just don’t want to know about.

  16. […] – Pygmi loris. Equidnas. […]

  17. inferniken says:

    so, who’s here from gamegrumps?

  18. No. says:

    Pushing down on me. Pressing down on you. You’re an asshole.

  19. doc says:

    I just wanted to know what an Echidna looked like now I’m messed up.

  20. Gotta love penis science

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  22. Riv M says:

    Used this article to prove that some Perry the Platypus R34 was inaccurate. Thanks.

  23. […] does have teeth in its stomach. So there, Mom! (Of course one of its echidna brethren species is reported to have four penises and you can imagine the trouble that will get you […]

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