Friday Weird Science: The Erection of the Ostrich

Dec 16 2011 Published by under Friday Weird Science, Uncategorized

I saw this last week, and while the world may have moved on, I CANNOT let the ostrich penis rest. So now it is time to talk about the ostrich, and about the head of the ostrich that never gets buried in the sand, if you know what I mean. I mean, the debate was CONTENTIOUS. WHAT was keeping those ostriches HARD? The world needs to know! Blood or lymph, blood or lymph, we need a study that will put this debate to bed (as it were). And now, a study has come! (You see that I did there). So of course I had to cover it. While other places have talked about the study, I felt they missed a couple of points (there are photos of EMU PENISES AND OMG THEY ARE WEIRD), and they missed something else. This MASSIVELY quote-worthy. Just you wait.

P. L. R. Brennan & R. O. Prum. "The erection mechanism of the ratite penis" Journal of Zoology, 2011.

(pictures below the fold NSFW. Well, if you know what you're looking at, anyway)

‘the lack of reliable information about the pres-
ence or absence of a vascular body in the ratites remains one
of the most striking defects in our knowledge of morphology
in birds’.

Seriously, the dude's right. HOW do we not know this by now?!

Anyway, you might be interested to know (I was) that most birds don't have wangs. Not at least, not wangs like we think of them. Instead, male and female birds have cloacas, a single hole in the butt through which they poop, pee, and mate (in birds, there's no such thing as the wrong hole).


When most birds go to mate, they put their cloacas (cloacae?) together in what's called a "cloacal kiss" (romantic, no!?). Sometimes it's very fast, but it's enough to get the sperm from the male into the cloaca of the female.

And then of course, you have birds where that doesn't happen. Where the male bird has a penis. There are several examples of this, ducks are the best known (and for good reason), but other birds, such as ostriches, have them too. The structure is a little different. Instead of a penis with an internal channel like most mammals, the ostrich has a penis that attaches to the bottom of the cloaca. Instead of an internal channel, there's no space inside the penis, instead there's an external groove that runs along it, and the sperm flows along the groove from the male's cloaca to the female.

(The authors note that this penis, when rigid, is 40 cm long. That's 15.7 inches. I'll let you contemplate that for a minute)

But of course, this penis needs to stay RIGID. How does it DO it? Where does the erection come from?

In mammals (and reptiles, some of which also have penises), erections are vascular. Blood flows out of the brain and into the penis where it builds up in spongy tissue, forming an erection. But the question in the ostrich was this: is it blood? Or is it LYMPH?

Lymph is a whitish/clearish fluid which circulates throughout the body, transporting things like bacteria which need to be destroyed, taking extra fluids back to the circulation, lots of things. It's a lot like blood plasma in what it's made of (except without the blood cells to make it red). But unlike the blood, lymph, though it circulates, doesn't get PUMPED in large bursts, it's moved instead by the contraction of smooth muscle that moves it slowly around.

But back to ostrich erections. Blood or lymph? There's a nice bed of blood vessels down there that would do the trick, but there's also a big bunch of lymph producing structures. The authors had to KNOW (don't we all). So they got an ostrich penis and a few emu penises for good measure. And of course...

We also use histology and direct
manipulation of fresh penises to suggest how the lymphatic
erection mechanism works in these large ratites.

I would love to meet these authors at a conference. The stories they could tell. "So, one time, I've got this ostrich by the dick, see, and..."

Anyway. It turns out that ostriches and emus have very different penises. The ostrich penis is like this:

You can see that the penis curves slightly, it's got spongy structures on the inside that fill with fluid (blood or lymph? We're getting there!) and one side is smaller than the other, making it curve.

While an emu penis is more like this:


Anyway, the scientists looked at the inside of the penises, and saw large amounts of lymphatic bodies and tissue, along with lots of fibrous stuff as well (which keeps the ostrich penis rigid all the time, even when not actually erect). They concluded that the erection of the ostrich (and the emu) was in fact lymphatic, not vascular.

Ok, so what? Well, this means that ostriches are like other birds with penises, all of which use lymphatic erectile mechanisms. This means that this is a mechanism common to birds, and the vascular one evolved in reptiles later (though birds and reptiles related as they are makes me wonder...did T Rex have a penis?! WHOA...). So the next time you see an ostrich running proudly across the wild...think of that dude, proud and free. And of his lymphatic penis.

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