Birds accept them, bees have them, fifty-fifty regular erstwhile fleas take them, merely in the creature kingdom, no penis is exactly like the side by side. Across vastly different species and ecosystems, unique environmental pressures take allowed creatures of many species to evolve an assortment of shapes and sizes—from the electrical bluish penis of the leopard slug to the bluish whale's ten-foot phallus.

The more scientists learn about penises, the more they realize how varied sex organs are. Just inquire Emily Willingham, a biologist and journalist who's been studying penises for over a decade. Her book, Phallacy: Life Lessons from the Animal Penis, hitting shelves in September. Phallacy plunges readers into the wild and wacky world of animal ballocks while exploring the social and cultural significance of penises equally symbols of power and identity.

Penises have been a longstanding subject of scientific fascination, and they're far more studied than vaginas. One caption for this inquiry gap, says Willingham, is "because of who has been request the questions until quite recently, and who's been deciding how those questions should be answered."

Typically, a penis helps male person animals reproduce sexually with a female—however, exceptions exist. Gender and sex rarely fit into tidy categories and animal penises are no dissimilar. Many of the creatures packing the most surprising phalluses are hermaphrodites, meaning they also have female reproductive organs.

"There's not a binary that is categorically i affair or the other when information technology comes to genitalia," says Willingham.

These blurred lines often give rise to nature's most fascinating sexual organs. Here are eight penises that are as cool and surprising every bit the creatures that wield them:

Heads Above the Rest

An echidna, a small spiny creature with a long nose, walking on gravel substrate
Echidnas accept a four-headed penis, though merely two heads are put to utilise at a time. pen_ash via Pixabay

Sometimes one just isn't enough. Or so it seems for the echidna, a spiny egg-laying mammal, which has evolved a four-headed penis. During copulation, echidna penises operate on a role-time schedule: half the penis temporarily shuts downward while the other ii heads are responsible for fertilization. But those extra two heads aren't there simply to prove off. Next time the echidna mates, he'll alternate which half he uses.

By shutting down half of their penis at a time, male echidnas fit perfectly with the female person's two-branched reproductive tract. This creature'due south coat of quills don't spare its genitalia, which features penile spines—a horrifying frequent trait in the creature kingdom (even humans once had them) which may increase fertilization success or trigger ovulation.

Getting Handsy

Two Atlantic spotted dolphins swimming underwater in the Bahamas
Dolphins accept particularly dexterous phalluses. Brent Durand / Getty Images

Dolphins are known for their intelligence, promiscuity and absurdly dexterous penises. They have a prehensile penis, significant information technology can swivel, grab and grope, much like a homo hand. A prehensile penis helps males navigate the complex, labyrinth-like reproductive tracts of female dolphins.

Dolphins don't just utilize their penises for baby-making, either. Bottlenose dolphins frequently copulate for pleasure, and often with members of the same sex. Dolphin sex doesn't last long, simply about x seconds, but males can ejaculate multiple times an hour.

Fencing With a Phallus

A black flatworm with vibrant pink edges, underwater
This flatworm engages in penis fights. Jens Petersen via Wikimedia Commons under [CC BY-SA three.0]

En garde! Many animals use their penises for love, but flatworms also use theirs to fight.

Like many organisms with intriguing phalluses, flatworms that engage in penis fights are hermaphrodites—just one instance that showcases how a sex binary organisation fails to account for the range, fluidity and diversity of many organisms. Some species of flatworm engage in this duel to see who can inseminate the other.

Their two-headed penises resemble tiny swords, and battles tin last for up to an hour as they take turns attempting to stab the other. The winner pierces the flesh of the other flatworm to deposit their sperm, something scientists refer to as "traumatic insemination."

Mating tin be competitive, with a single flatworm fertilizing another. In other cases, like with the tiger flatworm, they tin can play both roles: each flatworm gives and receives sperm from its partner.

Whale Hi There!

An aerial photo of a blue whale surfacing for air against a dark ocean backdrop.
Blue whales have the largest penis in the brute kingdom—around 8 to ten anxiety. NOAA Photo Library via flickr under [CC BY 2.0]

Bluish whales are the largest animal to ever roam the globe, and they certainly accept the phallus to match. Blue whale penises range between eight and x anxiety, with a pes-long diameter. Each of its testes along can weigh up to 150 pounds and can ejaculate gallons of sperm in a unmarried go.

Whale penises are so famously oversized that in Moby Dick, Herman Melville suggests using the skin of a sperm whale'south phallus as a floor-length apron to stay tidy while skinning the rest of the whale. We'll have to take Melville's word on that one.

Always Within Reach

A cluster of barnacles growing on the shells of muscles
Barnacles have penises nearly viii times their trunk length. Stux via Pixabay nether [CC0]

The blue whale might accept the world's biggest penis, but size is relative. Barnacles have the biggest penis-to-body size ratio, with genitalia near viii-times their full body length.

Barnacles are stuck in place for life, so they employ their super-long penises to reach other nearby crustaceans, blindly depositing sperm inside their neighbors. Like flatworms, barnacles are hermaphrodites that tin fertilize others, be fertilized or both.

Scientists have found that barnacle penis features change based on where they live. Those in rougher waters have shorter, stouter penises, while those in calmer areas have long, slender penises.

If humans had the same penis-to-body-sized ratio equally barnacles, our penises would be as long as a humpback whale, so almost 50 anxiety in length, says Willingham.

Armored and Amorous

A single red colored bed bug on a while backdrop
Bed bugs stab their partner during copulation. Centers for Disease Control and Prevention via Wikimedia Eatables under [CC0]

Bed bugs are famous for their aggressive, stabbing sex. Sometimes, overzealous males impale females with their saber-similar penis in the process.

Willingham explains that this violent process has caused bedbugs to evolve "something very vagina-like where they tend to become stabbed." This special less-armored area of their abdomen might minimize harm as the male injects his sperm into the female'due south circulatory system.

Gender-Bending Genitals

A eyeless cave insect with wings that is the size of a flea
Females of this cave insect species wield a penis-like organ. Biodiversity Heritage Library via Wikimedia Commons under [CC0]

Not much shocks Willingham about beast penises anymore, only she says she was surprised to acquire well-nigh a microscopic, eyeless cave insect, which upends how scientists understand sex.

Males of the species have a vagina-similar pouch containing sperm, while females accept a special penis-like organ that penetrates and vacuums upward sperm from the male.

Unlike other species that use a similar process—collywobbles, mites, beetles—males of these species don't have a similar penetrative organ, only the females practice, says Willingham.

A Temporary Tool

A bright red sea slug with a white underside, white spots and antennae swims underwater
This sea slug has a single-employ penis. Bernard Dupont via Wikimedia Commons under [CC BY-SA 2.0]

Meet Chromodoris reticulata, a type of bounding main slug, that has to reckon with a scary reality: sexual practice means maxim farewell to their penis. At least, for the twenty-four hour period.

Chromodoris reticulata are hermaphrodites and fertilize each other simultaneously during sex. Each has a three-centimeter-long schlong, but they only extend a centimeter of their penis when copulating. After sexual practice, they shed their single-use penis into the body of water'southward abyss. But this loss doesn't hateful their sex life is over: they have at least 2 more disposable penis segments hidden away. As soon as 24 hours later on, the slug will be dorsum in action.

How's It Hanging?

A leopard slug with dark spots and antennae on the edge of a log
Leopard slugs sport giant electric blueish penises. Cimabue via Pixabay nether [CC-BY]

Sometimes, penises pose logistical challenges. That is certainly the case for the leopard slug, which is so well-endowed that information technology has to go to farthermost measures to reproduce.

Mating leopard slugs dangle from branches by a shared rope of their own slime with their penises hanging below. As hermaphrodites, these slugs inseminate each other during sex so, once the action starts, two penises are on brandish. And their penises are easily spotted: They're electric blue and roughly the size of the slugs themselves.

"You just demand to go look that one up," says Willingham. You can meet a video of the slugs in action here.

The human action is a messy tangle, only nothing goes to waste. Once copulation is consummate, 1 partner slurps down the slimy sex activity rope as a post-coitus snack.

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