The weirdest and wildest mating rituals in the animal world, from bed bugs to giraffes

Have you ever wondered which animals get the freakiest between the sheets?

The answer to that is, literally, probably bed bugs.

But what about octopus? Why do lobsters shoot urine from their faces? And what is “penis fencing”?

If these are the questions keeping you up at night, read on.

Let’s start with ‘penis fencing’

The sport of fencing — where opponents spar using modified swords or “foils” — is thought to have emerged around the 14th or 15th centuries.

But in nature, it existed far longer.

pseudobiceros is a genus of flatworm — flat, soft-bodied, aquatic animals — that also engages in fencing.

But unlike the human sport, flatworms don’t use “foils”. They use their penises.

The other difference is that in “penis fencing”, the loser ends up pregnant.

A colorful flatworm.
Flatworms fight with their double-pronged penises in order to not fall pregnant.(Getty Images: hansgertbroeder)

pseudobiceros are hermaphrodites — the majority of the body mass of species like the Persian carpet flatworm (Pseudobiceros bedfordi) comprises both testes and ovaries.

During battle, each assailant exists as a kind of Schruhdinger’s flatworm, wherein both animals are simultaneously the potential father and mother.

The first penetration decides their fate.

A successful strike almost anywhere on the body sees sperm injected into the skin, where it will migrate through pores to fertilize the eggs of the disappointed mother-to-be.

Once the deed is done, the “father” exits the scene to fence again, while the expectant mother will gestate their unwelcome clutch for around 10 days.

In the world of flatworms, carrying fertilized eggs is laborious, and gestation puts a temporary hiatus on seeking opportunities to further spread one’s genes. So flatworms will fight ferociously to avoid that fate.

Whole lotta lobster

Here’s a sentence you probably didn’t think you’d read today: female lobsters urinate out of holes in their face to show a male they’re interested in mating.

And that’s only the start of their freakiness.

Lobster in an artificial kelp forest.
Lobsters excrete urine from nephropores at the base of their antennae.(IMAS: Cayne Layton)

The urine, which is expelled from holes known as nephropores at the base of the lobsters’ second antennae, contain pheromones to convey her gender and potential suitability as a mate.

“They have these remarkable, weirdly oriented organs which are the equivalent of our kidneys basically,” says Tomer Ventura, a scientist working in crustacean aquaculture at the University of the Sunshine Coast.

“They’re situated pretty much in their cheeks under the antennae.”

Dr Ventura, who has pioneered gene-silencing technology that can be used in commercial aquaculture to produce a single-sex population of crustaceans, says that in wild lobsters, the dominant male sits in a den from where he vets potential suitors.

To make sure he cops a full blast of the spicy pheromone mix, the female uses her gills to create a current, wafting it in his general direction.

“She squirts her urine directly into the den where the dominant male is,” Dr Ventura says.

If he’s picking up what she’s putting down, she’ll be invited inside, where he’ll provide protection while she removes her carapace — her shell — replacing it with a fresher, cleaner model.

The courting ritual has mostly been studied in the American lobster, Homarus americanusand while it might be the sort of behavior you’d expect from American crustaceans, it’s also true of our own spiny lobster, among others, Dr Ventura says.

A colorful lobster.
Female lobsters use urine to communicate their suitability to potential mates.(Getty Images: Humberto Ramírez)

He says in lobsters, the male produces a spermatophore — a capsule of sperm, which also contains a protective gelatinous matrix that sets like a sticky concrete on contact with water.

The female carries that spermatophore around with her until she’s ready to release her eggs.

“The female releases virtually millions of eggs while scraping the surface of the spermatophore to reveal the intact sperm.

“[At the same time she’s] curling her tail to release that cement that sticks the fertilized eggs onto her swimming legs in the tail.”

This is my Flehman face

At this point it’s probably safest to assume there’s urine involved unless stated otherwise.

In the case of giraffes, males will smell the hindquarters of the female, often flaring his upper lip in what is known as a “flehman response”.

While it has the appearance of a grimace, the flehman response draws air into the vomeronasal organ — an olfactory sense organ in the nasal cavity above the roof of the mouth — which assists in the detection of pheromones.

He’s checking to see if she’s ovulating and ready to mate.

But if he’s not convinced, the male will encourage her to urinate by rubbing her hindquarters.

A male giraffe drinking a female's urine.
Male giraffes will taste the urine of the female to see if she’s ovulating.(Getty Images: Kim Marriott )

He’ll then taste her urine, and if he picks up the signals he’s after, will follow her around in the hopes of mating.

In the wild, he won’t be the only one showing an interest though, and will need to fight off other males using his huge neck to pummel his rivals, while attempting to plunge his ossicones — horn-like appendages on his head — into their flesh.

They’ve been doing this in our beds?

If you’ve ever had bed bugs and thought, “gross, I’m sharing my bed with bugs”, strap in.

Humans and bed bugs have a long history.

Research suggests bed bugs were originally bat specialists, feeding on the winged creatures in caves in Africa.

But as our ancestors moved into caves millions of years ago, bed bugs decided we were a tastier option and shifted their allegiance.

As humans spread from Africa and across Eurasia, we took the bed bugs with us.

A bed bug under a microscope.
Bed bugs are able to produce more young if they’re able to access greater amounts of our blood.(Getty Images: Peter Finch)

We can’t really justify the bed bugs for feeding on our blood though. They need all the energy they can get for mating.

Adult bed bugs become most active during witching hour — between about midnight and 5am.

They locate their sleeping hosts by detecting exhaled CO2 and body heat, and once fed, are in the mood for love.

Cue Barry White? Not quite.

The male bed bug stabs his reproductive organ through the right side of the female’s body wall into what is called her Organ of Berlese.

The male’s sperm enters the body cavity, migrates to her ovaries and fertilizes her eggs.

Females may be stabbed multiple times by different males during one outing, and will retreat to recover, lest their traumatic mating prove fatal.

How many eggs and offspring she is capable of producing depends on how much blood — of yours — she’s able to consume in her lifetime of between 100 and 300 days.

Nine brains, three hearts, borrowed time

Of course octopus are on the list. They’ve got eight legs, nine brains and only a year or so to use them.

Research has observed at least one female octopus strangling her partner during copulation.

A red octopus with white spots.
Once the deed is done, the female usually sits on her eggs for a period of one to three months.(Getty Images: A. Martin UW Photography)

Another study observed a small male octopus cyanea, also known as big blue octopus, mating with a larger female 12 times over a three-and-a-half-hour period while she foraged for food in Palau, Micronesia.

Perhaps fed up, hungry or both, on his 13th attempt, she suffocated him, took him back to her den, and “spent two days cannibalizing him”.

Michael Amor, a research assistant in the aquatic zoology department at the Western Australian Museum, says it’s probably not a great surprise that octopus sometimes eat their mates.

“They’re not the most social beings. There might not be that [emotional] barrier to feeling you shouldn’t eat your neighbor,” Dr Amor said.

Research published last year also showed female octopuses throwing shells and other debris at males to ward off their unwanted advances.

It probably makes sense that a female should be discerning about who fathers her children. It’s typically her only shot at reproduction, and the egg-brooding period can be especially traumatic.

For most shallow-water octopus species, once the deed is done the female sits on her eggs for a period of one to three months.

Even in these instances, females have been known to eat their own arms rather than leave the nest in search of food, according to Dr Amor.

But in deeper water, where conditions are harsher and colder, things can stretch out much longer.

Back in 2014, research published in PLOS detailed the exploits of a female deep-sea octopus — Graneledone boreopacifica — in 1,397 meters of water on a sloping wall in the Submarine Canyon off central California.

A pale octopus in deep water.
A deep-sea octopus was recorded sitting on her eggs for over four years.(Supplied: PLOS One)

Using a remotely operated vehicle, scientists first encountered the female over a period of a few weeks, first without eggs and then shortly after having laid them.

Seizing the opportunity to measure the breeding time of a deep-sea octopus, the researchers endeavored to monitor how long she sat on her clutch.

Four years later, they were still watching.

The eggs had continued to grow, whilst she was diminishing in size and had become pale, with cloudy eyes and slack skin.

On the researchers’ final visit, after 53 months, only the “tattered remnants of empty egg capsules” remained in their place.

It was the longest-known egg-brooding period for any animal.

One-way ticket to the EAC

Olaf Meynecke spent years researching mud crabs and says after what he’s seen, he can no longer eat the feisty crustaceans.

For Dr Meynecke, a marine ecologist at Griffith University who now studies whales, it wasn’t so much how they mate as what they eat.

“They’re literally turning rotten meat into their own meat, which we then love to eat,” he says.

Mud crabs on the Logan River can carry the white spot disease, although the virus is not a threat to human health if eaten
Gravid female mud crabs have been found more than 50 kilometers offshore.(ABC Rural: Marty McCarthy)

On the bow-chicka-wow-wow scale, mud crabs are about mid-range, but there’s some research, including some conducted by Dr Meynecke, that earns them the final place on this list.

Typically mud crabs hang around coastal, mangrove-lined waterways in the tropics and sub-tropics.

When it comes to mating, the male jumps on top of the female, and will basically hitch a ride around with her for a few days.

In some instances, the males have been known to pick up molded females and carry them around for several days while mating.

Similar to lobsters, the male deposits a spermatophore capsule that the female carries with her until she’s ready to fertilize her eggs.

Not known to be great long-distance swimmers, the females typically hang around their estuaries for most of their life cycle.

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