On Valentine’s Day, a Dive into the Weird World of Animal Sex

By Mike Weilbacher, Executive Director

It’s Valentine’s Day, and while we’re canceling our scheduled evening program, I thought I’d share the strange tales of amorous animals.  Nature is incredibly wonderful, but also incredibly weird. 

Take the clownfish, for example, so famously depicted in Finding Nemo, that sweet name abducted by last week’s horrific storm.  All clownfish are born male—not a girl in the bunch.  They live in and around anemones, stinging relatives of corals and jellyfish; plantlike but actually animals, anemones are unable to move anywhere.  So clownfish don’t go very far either.  (And sadly, rarely go on any adventures of any kind.)  Clownfish, immune from anemone stings, groom their host to remove dead and dying “branches,” and in exchange dine on dead fish left behind from the anemone’s handiwork. 

A large female clownfish rules the anemone, a colony of males of a variety of ages and sizes hanging out with her, competing to mate, the largest using winning.  But when the female dies, the next-in-size clownfish, the largest male, simply changes sex, and becomes the colony’s official female, establishing a whole new pecking order.  (So in the movie, when Nemo’s mom disappears, the dad simply becomes the mom.)  And it turns out this sequential hermaphrodism is not too rare in the wide, wide world—lots of species do it. 

Fireflies are cool.  A flashing field of fireflies is a huge stag party, acres of males flying the friendly skies.  The females—bigger, abdomens overloaded with eggs—cannot fly, but sit watching the signals, as males flash their codes to potential mates, each firefly species using species-specific signals to seduce mates.  When the female sees the right kind of male fly by, she gives him the correctly coded answer—and mating ensues.

Except one species knows the correct answer to a second species of firefly—she’s cracked his code.  When she’s hungry and sees one of these hapless guys flashing by, she gives him the answer he’s looking for.  He lands—and she devours him, using his protein to create her eggs. 

Which reminds me of the honeybee.  A hive is almost completely female, thousands of female workers grooming and caring for one supersized queen, the egg-layer of the group, the workers moving through life tackling a sequence of jobs, beginning as, say, a funeral bee carrying dead bees out of the hive, and ending as a field worker collecting nectar and pollen. 

There are male bees, drones, creatures unable to perform any useful jobs, existing for one purpose: their sperm.  Drones of many hives hang out in designated areas—like teenage boys in front of the Wawa—waiting for a potential queen to fly by. 

When a queenless hive raises a new ruler, she takes a maiden voyage into that drone cloud, and ostensibly the fastest, strongest drone succeeds.  Tragically, he dies upon ejaculation, most of his innards flying out with the sperm packet to form a plug that prevents the queen from ever mating again.  Yup, it’s one and done for both.

And when autumn comes, drones become a liability, unable to work or feed, not needed during the long, cold winter.  Drones tap the antennae of workers for food, but the workers walk away, refusing the request.  In late autumn, funeral bees spend a fair amount of time dumping the bodies of starved, dead drones outside the hive’s doors.

Speaking of all females, you’ve likely seen photos of anglerfish, a chunky deep sea fish named for the projection on its head that it dangles in front of prey, using a little worm-like lump on this appendage to lure unsuspecting fish into its jaws. Scientists were once intrigued that all anglerfish were female—and that all seemed to have a small parasitic creature stuck to its body.

Turns out the parasite is a male.  Its mate.  Anglerfish inhabit the deep ocean bottom, where it’s bleak and black and speed-dating doesn’t occur.  Males hatch as very small versions of the female, but without a stomach.  Once born, they immediately seek out mates; when they find her, male bites into female and releases an enzyme that digests their skin.  He fuses onto the side of her body, wasting away to become this odd lump literally glued to her side.  And when the female is ready to spawn, he is there, releasing the sperm she needs to fertilize her eggs.

Let’s stay in the ocean one more time. Male octopuses and squid have a breakaway arm that holds his sperm packet.  In mating, the male uses this arm to reach into the female’s body cavity, placing the package carefully inside, whereupon it breaks off.  Like the anglerfish, early naturalists thought female octopi all had parasitic worms in them, and actually gave the male arms formal scientific names.

But the argonaut, a small cousin in this clan, takes this strategy on strange step further.  His mating arm is kept tucked in a pocket below his eye.  When he spies a suitable mate, he approaches her tenderly, and if she is receptive, the mating arm suddenly explodes out of his body, killing him instantly, the detachable arm taking on a life of its own, swimming to the female, clinging to her, and worming its way into her insides.  Some female argonauts have actually been found with multiple arms in her cavity, her collection of conquests.  But a free-swimming penis-like structure is, let’s face it, the stuff of science fiction.

Last example: red-sided garter snakes.  A female awakens from a long winter’s nap, and begins giving off a pheromone that males find irresistible.  Quickly, a mating ball of hundreds of writhing snakes forms, the female surrounded by scores of hopeful males—put THAT in the next Indiana Jones movie. 

And so it goes through the animal kingdom. If you’d like to continue researching this, er, “fertile” field, check out the following: banana slugs (the most highly endowed animal of all), flatworms and their penis jousting, the male frigate bird’s display, and perhaps the horniest animal of all time, our cousin the chimp-like bonobo. 

Happy Valentine’s Day.

Mike Weilbacher directs the Schuylkill Center for Environmental Education in Philadelphia, tweets at @SCEEMike, and can be reached at mike@schuylkillcenter.org.