Clownfish swimming under water in the ocean.

Fascinating facts about mating in the animal kingdom

Written by:
July 21, 2020

Fascinating facts about mating in the animal kingdom

Reproduction is the common thread that unites all living things—the individual is doomed to die, but with reproduction, the species lives on. Everyone over a certain age knows how humans make babies, and for many animals, the process isn't that much different. For many others, however, the process is, well, a process.

A handful of animals choose one partner for their entire lives. Many others are open to all takers. Some mate all year long, others are fertile only for a few hours. Some are highly selective and require one gender to perform elaborate rituals like dancing, strutting, and structure-building for the other gender to even give them a look. Others do it as frequently as possible with as many in their species as possible. More gruesomely, many animals murder after mating. Some others have to die in order to do it. Others do it literally until it kills them.

Monogamy exists in nature, albeit rarely, as do homosexuality, infidelity, and ferocious jealousy. As with people, many young males in the animal kingdom strut, preen, and otherwise try to impress females, often in vain. Also familiarly, females often choose males based on attributes like strength or the ability to provide resources.

There are, however, plenty of differences. Some species are highly social and structured like ours—but their societies are dominated completely by females. Other species have sexual traits of both genders. Others are born as one gender but can switch when needed.

Using sources like nature publications and research reports, Stacker compiled a list of 30 animal mating habits that defy the imagination. From the ocean floor and the frozen poles to the rainforest interior and parched desert, these animals continue their species in some of the most unusual ways.

Keep reading to learn about how the birds, bugs, lizards, monkeys, mice, spiders, and fish make more of themselves.

Black widows love their mates to death

Thanks to its ominous appearance and brutally venomous bite, the black widow spider is one of the most feared creatures on Earth—but it's especially scary to its mate. The species got its name because female black widows are known to kill and cannibalize their male lovers once the act is complete.

Flatworms engage in 'penis fencing'

Marine flatworms are hermaphroditic. When mating, they engage in a showdown that biologists call "penis fencing," duking it out in an underwater sword fight. Whoever stabs and inseminates the other first wins, not only dodging a ghastly wound, but gaining all access to the inseminated eggs inside the other.

Female barklice have painful phalluses

The disgusting insect known as Neotrogla barklice is known for a biological switcheroo. Sperm-producing males evolved with vaginas and egg-producing females wound up with phalluses—spiked phalluses, at that. After aggressively seeking out male lovers, the female roughly inserts her barbed phallus and doesn't let go until she's been inseminated multiple times.

Bonobos are sex-crazed close human relatives

Like the Neotrogla barklice, the endangered ape known as the bonobo tosses the concept of male supremacy out the window when mating. Sex dominates the social culture of bonobos, who have sex with both genders with incredible promiscuity—they do it to avoid violent aggression, as a form of currency, to make friends, and just to pass the time. Females are not monogamous by any means, and since they don't discriminate, males have no way of knowing which baby bonobos are theirs and therefore aid in raising the entire nursery, a mating trait that has created a social structure dominated by the chimp equivalent of women.

Clownfish can change genders

Clownfish, known worldwide for "Finding Nemo" fame, are monogamous and are born male but can turn themselves female. A single dominant female leads a group of males, and if she dies, the biggest male switches genders and rules the school as a female. Males prepare nests and try to woo the female with an underwater dance, and if she goes for it and lays eggs, the male not only inseminates them, but does most of the egg-sitting until they hatch.

For manakins, the female has her choice

In a kind of avian speed dating, female manakins venture into sex dens called leks, where they observe a multitude of males all vying for their attention through a mating ritual called lekking. Since food is plentiful, females don't choose male mates based on their ability to provide resources, but instead, make their decision based on the awesomeness of their leks. When lekking, males put on elaborate and extended displays of acrobatics and nonverbal sounds—they've developed specialized feathers just for that purpose—which the female observes until one impresses her enough to choose him.

Albatross mate for life, but often stray

Only a tiny percentage of animals pair up with one mate for life. Among them are the albatross that wander at sea for extended periods and return to their mating grounds every other year to reconnect with their life partners. That bond, however, does not mean they're monogamous. About 14%–24% of chicks are fathered by third-party albatross dudes.

Bedbug sex is quite unpleasant

As if bedbugs weren't unlikeable enough, they up the repulsion ante through a mating ritual known as traumatic insemination. Males bypass their female counterparts' perfectly functional reproductive tract and instead stab their daggerlike penises through the female's abdomen in order to achieve insemination.

Shingleback lizards have only one true love

In the animal kingdom, monogamy rarely makes strategical sense, and only a tiny percentage of animals on the planet stick with one sexual partner for life. The shingleback lizard is among them. They spend most of the year living alone, but return to their monogamous partners in the fall between September and November.

Some octopi rely on disguises in order to copulate

The tiny octopus known as Abdopus aculeatus displays a unique behavior known as guarding, in which males pull sentry duty around mating dens where males and females copulate. Some males, however, slip past the guards by disguising themselves as females to get in on the action, which the true female will frequently let them do if the ruse works.

Only the best neck-fighting giraffes will mate

Unlike many animals, giraffes don't have a breeding season—they're ready to rock and roll whenever the females are fertile. Males figure this out by smelling and sometimes drinking the urine expelled by females—but mating isn't a given. In order to earn the right, male giraffes duke it out in violent neck-to-neck battles to determine which one is stronger and therefore more attractive to the female.

Humpback whales keep it on the down-low

Female humpback whales are not monogamous and hook up with several partners during the mating season while rarely interacting with other females during that time. Many adult males are covered in scars, most of which come from intense battles that, like giraffes, they stage for the right to mate. What makes them so unique is their incredible discretion—no human being has ever witnessed humpback whales mating.

Antechinus mates until it kills him

The tiny mouselike marsupials known as Antechinus is more compulsive about sex than even the bonobo. The Antechinus remains chaste until mating season arrives. Then the males seek out frenzied mating sessions, often lasting 14 hours, with as many females as possible, and doing nothing else until their immune systems collapse, they develop gangrene and infections, their bodies dissolve, and they die attempting to pass on their genes.

Prairie voles have family values

Not only do prairie voles partner up for life, and not only are they monogamous—two biological rarities in and of themselves—but they're actually devoted parents. Both parties stick around to raise their young, and if the male slacks, the female will put him in check by yanking the scruff of his neck. When one dies, the other displays emotional grief.

Lovebirds start with dinner dates

As their name implies, lovebirds are heavy on romance, with the male feeding the female at the start of courtship—kind of like the avian equivalent of taking a date out to dinner. Then they go on extended mating benders, which take place several times a day for days on end. It doesn't take long—a clutch of eggs can be laid as soon as three days after mating.

For hippos, power is everything

In the unforgiving hippo world, it pays to be a big, strong man. Females are fertile for only about three days a year, and about 90% of all males will never know what it feels like to mate. That privilege is reserved only for bulls who rule a territory, and those dominant males will each take up to 10 female cows, leaving lesser males to play the role of wallflower.

Anglerfish live to mate—but often die trying

One of the most imposing-looking creatures in the sea, anglerfish are known for giant mouths filled with dagger teeth and, of course, their trademark illuminated lure—but those are the females. Their male counterparts are far less imposing—in fact, they're so underdeveloped that most can't even digest food. Upon birth, their sole purpose is to find and inseminate a female, but most will wander through their watery world blind and feeble before starving to death as virgins.

Sound, not size, matters for water boatmen

Water boatmen are tiny swimming insects that hold the title of being the loudest animal on Earth relative to its size—and he makes his music, you guessed it, to attract females. By rubbing their penises against their abdomens, male water boatmen can generate a sound that reaches 99.2 decibels. That's loud enough that a person standing on a riverbank can hear his mating call at the bottom of the water.

Sage grouse seduce on the dance floor

Like manakins, sage grouse are known for their elaborate mating dances, which they perform to entice fertile females. Setting up cameras where they live to observe the display has become a kind of ritual among bird-watchers. Since females only mate with a small percentage of the male population, competition is stiff. Every morning during mating season, males wake up early to fan their tail feathers, pop their specialized air sacs, and strut around with their chests puffed out, hoping for a sage grouse of the fairer sex to take notice.

Birds of paradise work hard to show off

One of the most mysterious animals, birds of paradise live only in New Guinea and a few tiny Australian islands—their largely inaccessible habitats make their behavior hard to document. What is known, however, is that they put on a ritualized mating dance that can rival even that of the sage grouse, with some kinds of birds of paradise contorting to shape-shift into seemingly different creatures altogether. Others smoosh their feathers down to form a ballerina's tutu while strutting for the attention of females deep in the rainforest jungle.

Garter snakes have a ball

Known officially as Thamnophis elegans, garter snakes are known for a bizarre mating ritual that, to the untrained eye, could be mistaken for something out of a horror movie. They form into giant "mating balls" made from masses of males that swarm a single female and jockey to achieve the correct mating position. When one lands it, he subdues the female with an oxygen-depriving kiss that makes her docile enough to inseminate, and then, as quickly as it started, the ball dissipates into individual slithering members once again.

Bowerbirds are interior decorators

Like birds of paradise, bowerbirds live only in New Guinea and a few tiny Australian islands. Also like birds of paradise, they put on an extensive undertaking as part of their mating ritual, but it has nothing to do with dancing. They build elaborate structures called bowers—hence the name—and decorate them with colorful objects like leaves, flowers, and even man-made items like plastic and glass, in order to seduce a female.

Male porcupines walk on pins and needles

An individual porcupine can bristle with 30,000 hollow, needlelike quills designed to embed themselves deeper and deeper into animal flesh—and these living pincushions put them to good use when it's time to mate. Females are fertile for only a tiny window of eight to 12 hours, and they announce their readiness by spraying the air with a musk that draws males from all around. They battle ferociously for the right to mate, but it's not really a right—if the female isn't satisfied with the victor, she'll block his mounting attempts with her quills.

Pufferfish make underwater crop circles

Deep on the seafloor in 1995, divers noticed perfectly symmetrical circles emblazoned with geometric patterns that they compared to underwater crop circles. It turns out, they were the hallmark of pufferfish mating. Males from a tiny species of pufferfish use their fins to create the designs to attract females, kind of like an underwater bower.

Garden snails wield phalluses from their heads

Like flatworms, common garden snails are hermaphrodites. When they mate, each one of them extends—from their heads—a phallus toward the head of the other. The two appendages entangle and one inseminates the other.

These spiders are regifters

Male nursery web spiders try to butter up females by offering them the gift of a fly or another unfortunate insect wrapped in a web cocoon. If she's not into it, she'll threaten him and send him packing. If she likes it, they mate—only for the greedy male to leave and take his gift with him.

Mantis murder and cannibalize—but only sometimes

Female praying mantis are infamous for biting off the heads of males and devouring their bodies after mating, but they get a bad rap—sort of. They don't always murder and cannibalize after mating, only if they're hungry or agitated, so it just kind of depends on her mood.

Queen bees are sperm hoarders

A virgin queen honey bee mates by flying to a location where thousands of drone bees are waiting and she mates with several of them while in flight. When a male is finished, he pulls away, tearing off his appendage and leaving it inside the queen—which quickly kills the male. The females then store as many as 100 million sperm in their oviducts and use them to fertilize eggs as needed throughout their lives.

Female hyenas can be difficult mates

Female hyenas are larger, more aggressive, and have more testosterone than males—it's easy for casual observers to mistake one for the other. The female has a dummy phallus that looks just like the real thing. Because of their strength and aggression, and because their appendage often gets in the way, males often have a hard time successfully mating.

Penguins get undue credit

Penguins are known for developing lifelong, loving, and monogamous relationships, but most of that is actually flightless bird urban legend. While many do choose partners for life, most species cheat frequently, including to sometimes engage in homosexual sex. Oh, and females are infamous for kidnapping each other's chicks.

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