The Alligator Penis Is Permanently Erect, But Pops Out Only When Needed

The alligator penis doesn’t have an off setting. Unable to inflate with blood or lymphatic fluid, it instead maintains erection by being constantly rigid due to a dense network of collagen fibers inside the penile shaft. This means that rather than being flaccid and rising to the task of copulation, it’s permanently ready to pop out for a quick bit of fertilization, before being retracted out of sight again.

Alligator Penis In Action

Discovering the unique function of the alligator penis came as something of a jump-scare for a group of researchers, as you can witness in the below video which we really – really – don’t recommend you watch if you’re currently in the office. It shows Brandon Moore of Louisiana Tech University dissecting a freshly dead male alligator just as his scalpel makes contact with the pelvis nerve, releasing the alligator penis like a cursed Jack-In-The-Box.

Making sense of the alligator penis fell to Diane Kelly at the University of Massachusetts, who published a paper on her findings. Kelly had exposed the anatomical secrets of several penises within the animal kingdom, and solving the puzzle of the alligator penis involved working with deceased specimens at the Rockefeller Wildlife Refuge in Louisiana.

Alligator Penis Dissections

Her work revealed that the alligator penis doesn’t need to inflate, unlike those of mammals, birds, and other reptiles. Instead, it maintains a permanent erection by being built up of dense layers of collagen, the main structural protein in our connective tissues.


If you don’t know what an alligator penis looks like, it’s with good reason. They don’t permanently brandish them on the outside of their body like other animals, but instead tuck the 10-centimeter (3.9-inch), ghostly-white appendage behind something called a cloaca.

The all-in-one orifice gets its name from the Latin for “sewer,” and it’s the exit route for urine, feces, and anything that comes out of the reproductive organs. That includes the alligator penis, so how does it go surface-side when the time comes to make some baby gators?

How Does The Alligator Penis Work?

Weirdly, Kelly found the alligator penis has no musculature, being a rigid structure that sits on the levator cloacae without actually being attached to it. By manipulating the levator cloacae in dead animals, Kelly was able to recreate the explosive action of the alligator penis we saw in Brandon Moore’s video.

This indicated that it was this muscle that enabled the permanently erect penis to fling out with aplomb by squeezing the cloaca, forcing the dense-collagen penis out. When the muscle relaxes, the ligaments pull the alligator penis back in.

So there, that’s something you know now.

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