8 Weird Animal Penises

Penis, the primary sexual organ that male and hermaphrodite animals use to inseminate sexually receptive mates (usually females and hermaphrodites respectively) during sex. Almost all species use some variation of the organ to transfer sperm into females' eggs in order to create more offsprings.

However, thanks to evolution, some species have come up with some really remarkable and weird innovations in penis design. So, let's see some of the world's weirdest wieners!

1. The gigantic penis
You have probably heard the joke about elephants or donkeys having a fifth leg. The truth is that relative to their body size, barnacles are the clear winners. Due to their immobile lifestyle, barnacles have evolved to have remarkably long penises [up to 40 times their body-length] to ensure genetic transfer between isolated individuals.

See that long-fillament? Guess what it is!
Credit: Chris Neufeld

As for more complex and everyday animals, the gold medal goes to the Argentine lake duck (Oxyura vittata) which has a penis that when erect can be as long as the animal itself. This is even more surprising considering that most male birds have no penis at all! The best endowed lake duck ever found had a 42.5 cm long erect penis.

Credit: K McCracken/ Nature

Extra Fact: Male ducks have corkscrew-shaped penises cause female ducks have corkscrew-shaped vaginas

2. The Four Headed Penis
Along with the platypus, echidnas are the only surviving monotremes. The echidna is a weird animal for many reasons. It looks like a cross between a hedgehog, a platypus and an anteater, it has electroreception and it lays eggs despite its mammalian nature. Oh, yes! It also has a 4-headed-penis:

During mating, the heads on one side "shut down" and do not grow in size; the other two are used to release semen into the female's reproductive tract. Each time a male has sex, it alternates heads in sets of two. In case you wonder, the average erect size is 7 cm.

Jump to 00:17 for the kinky part

3. The Singing Penis

The lesser water boatman (Micronecta scholtzi) is a tiny 2 mm long insect found in freshwater ponds and lakes across Europe. In 2011, researchers made an unexpected discovery. Males produce their underwater courtship song by rubbing their penis along their ribbed abdomen. But what is more interesting is that this sound can be up to 99.2 decibels loud, a volume comparable to a passing freight train.

Micronecta scholtzi

Although most volume is lost when sound moves from water to air, it still remains audible to humans walking along the pond shore. For its size the M. scholtzi is considered the loudest of all animals.

4. The Double Penis
Male squamates (snakes, lizards and worm lizards) have a sexual organ called hemipenes. This is essentially a pair of two weird looking penises that come in a variety of shapes and sizes, depending on species. Often, the hemipenis bears spines or hooks, in order to securely anchor the male inside the female. Some species even come with a forked hemipenes (each hemipenis has two tips).

The hemipenis of a rattlesnake
Credit: Tess Thornton

5. The Piercing Penis (Traumatic insemination)
Traumatic insemination (or hypodermic insemination) is the mating practice of some invertebrates in which the male uses its penis to pierce the female's abdomen to inject his sperm through the wound into her abdominal cavity. Not surprisingly, the process is dentrimental [and sometimes lethal] to the female's health as it creates an open wound.

A prime example of traumatic insemination are bed bugs which reproduce solely using this method.

A male bed bug (Cimex lectularius) traumatically inseminates a female bed bug (top).
Credit: Rickard Ignell

6. The Detachable Penis
Like most octopuses, the argonaut octopus, a type of nautilus, has a rounded body, eight arms and no fins. But it also has a detachable penis! Yep, you read that correctly. The males use a modified arm, called the hectocotylus, to transfer sperm to the female.

During fertilization, the arm is first inserted into the female's pallial cavity and is then detached from the male. Obviously, males mate only once in their life.

Male argonaut (left) and argonaut penis (right)
Source

Fun Fact: The hectocotylus when found in females was originally thought to be a parasitic worm.

7. The Female Penis
The rule is, males have penises, females have vaginas. Or something like that. But every rule has an exception. The exception to this rule is Neotrogla, a genus of barklice noted for its reversed sex roles and organs, traits shared by all species of the genus.

 N. curvet mating (female on top)

Female Neotrogla possess a penis-like organ, called "gynosome", whereas males have a small, vagina-like opening. During mating, the female mounts the male and penetrates his small genital opening from behind. With her gynosome she extracts sperm and nutrient-filled seminal fluid from the male.

Fun Fact: A single mating session can last from 40 to 70 hours!

8. The Pseudo-penis
Finally we have the genitalia of female spotted hyenas. Elevated levels of testosterone cause the females to develop a penis like thing, called pseudo-penis. This appendage is essentially an enlarged clitoris capable of erection that can grow as long as 7 inches.

Female Hyeana Pseudopenis
Credit: National Geographic

The female also possesses no external vagina (vaginal opening), as the labia are fused to form a pseudo-scrotum. The pseudo-penis is traversed to its tip by a central urogenital canal, through which the female urinates, copulates and even gives birth. The walls of the pseudopenis become relatively thin and elastic in the late stages of  pregnancy, such that the female can deliver her 1 kg cubs without dying in the process.


Do you know of any other examples of weird animal penises? Shoot them up in the comments!

References & Further Reading
- "Biology of Barnacles". Museum Victoria. 1996. Archived from the original on February 17, 2007. Retrieved April 20, 2012.
- McCracken, K. (2000). The 20-cm Spiny Penis of the Argentine Lake Duck (Oxyura vittata) The Auk, 117 (3) DOI: 10.1642/0004-8038(2000)117[0820:TCSPOT]2.0.CO;2
- Sueur, J., Mackie, D., & Windmill, J. (2011). So Small, So Loud: Extremely High Sound Pressure Level from a Pygmy Aquatic Insect (Corixidae, Micronectinae) PLoS ONE, 6 (6) DOI: 10.1371/journal.pone.0021089
- Yoshizawa, K., Ferreira, R., Kamimura, Y., & Lienhard, C. (2014). Female Penis, Male Vagina, and Their Correlated Evolution in a Cave Insect Current Biology, 24 (9), 1006-1010 DOI: 10.1016/j.cub.2014.03.022
- Engh, A., Van Horn, R., Szykman, M., Holekamp, K., & Boydston, E. (2007). Courtship and mating in free-living spotted hyenas Behaviour, 144 (7), 815-846 DOI: 10.1163/156853907781476418