Alligators are still erect and weirder reptile genitalia
More than 10,000 species of reptiles of all shapes and sizes scurry and glide across Earth, from gartersnakes to crocodiles – and their nether regions are just as varied.
From spiky penises to multiple penises — or none at all — reptiles possess some of the most unusual mating gear on Earth. (Find out how lizard genitalia became a black market craze.)
Most current knowledge of reptilian genitalia focuses on the male parts, but scientists are increasingly turning their attention to studying their female counterparts – it’s just a bit trickier since the female parts are located at inside the animal.
two are better than one
Snakes and lizards have not just one, but two penises, called hemipenes.
University of Sydney researcher Christopher Friesen says having two hemipenes can benefit males during mating.
“In the case of the garter snakes I studied, being able to mate on either side of the female could be helpful in intense mating competition,” he says.
This is because the snakes form what Friesen calls “massive mating aggregations” in which anywhere from five to 100 males compete for a single female by searching for her in the mating ball. “It might be advantageous to be flexible on which side of the female a male is on, as they use the hemipenis closest to the female to mate with.” (See a pit filled with 75,000 mating garter snakes.)
And it’s not just men who overtake. Female lizards and snakes have two clitoris, or hemiclitores, which were first described in female monitor lizards in 1995 by W. Böhme as “miniaturized mirror images of male hemipenes”.
Hemiclitores and their functions are still “poorly understood” but should be considered a defining characteristic of female lizards and snakes, researchers Soledad Valdecantos and Fernando Lobo from the Universidad Nacional de Salta in Argentina reported in a paper. 2014 study.
Where none is better than one
On the other hand, the tuatara – a lizard-like reptile – has no penis at all.
Instead, the male simply mounts the female and places the opening of her cloaca – the cavity where the intestinal, genital, and urinary tracts meet in reptiles – over hers. This allows him to transfer his semen into his cloaca.
Most birds mate in the same way – the majority of male fowl are phallusless and instead deliver sperm by rubbing vent against vent. A notable exception is found in ducks, which have a reputation for being long and corkscrew-shaped penises and vaginas.
Ephemeral female penises
Australian researchers made a curious discovery last year while studying embryos of the central bearded dragon, a large lizard that lives in dry environments. It turns out that females temporarily develop the lizard equivalent of a penis while still in the egg.
“The way these females developed hemipenes, the equivalent of a mammalian penis, was decidedly bizarre,” said researcher Vera Weisbecker from the University of Queensland in output from Science Daily.
Females shed their hemipenes as they approach hatching. This research adds to what Weisbecker calls the “limited knowledge” of female reptile genitalia.
The hemipenes of lizards and snakes sport tiny spikes and hooks.
Scientists have some ideas as to why hemipenes exhibit this type of ornamentation. According to one hypothesis, the male and female genital form has adapted so that mating can only take place between a male and a female of the same species. The genitals of males and females of the same species fit together, and the spikes and hooks could help the male hold his hemipenis in place during mating.
A study found that these spikes and hooks can also increase the duration of copulation, thereby increasing mating success.
“I would emphasize that female genitalia need to be studied in order to fully understand the elaborative function of male genitalia,” Frieson says.
Always trained alligators
Male American alligators are always prepared. Most, if not all, other animal penises swell from a flaccid state, but alligators keep theirs permanently erect.
And that’s not all: the penis springs from inside the animal’s body and then bounces back like a rubber band. Diane Kelly, a researcher and animal phallus expert from the University of Massachusetts, told National Geographic in 2013 that this “elastic permanently erect penis” is “really weird”.
Kelly has a theory about how a “nearly free-floating” permanently erect penis with no muscle attached is able to emerge from the animal’s cloaca. After seeing this videoshe theorized that a pair of muscles cradling the penis – the levator cloaca – contract to force the penis out.
So far, the phenomenon has also been observed in Nile and Australian saltwater crocodiles. “We expect this to be true for all crocodilians,” Kelly says via email.
She is still working to obtain live, sexually mature specimens to test her hypothesis. Kelly notes that while the penis itself is permanently erect, the glans — that bulbous structure at the end — swells, and each species has its own unique look and shape.
Tina Deines is a freelance journalist based in Albuquerque, New Mexico.