Published: February 11, 2016

The Birds and the Bees: Craziest Animal Mating Stories

Kate Golembiewski, PR and Science Communications Manager, Public Relations


Cue up the Marvin Gaye—we’ve got everything from moonwalking birds to snails shooting “love darts,” all in the name of keeping their species going. It’s Valentine’s Day, Field Museum style.


1. Bowerbirds roll out the blue carpet

Ever frantically cleaned up before a date came over? Satin Bowerbirds get the importance of having a nice place. Males build elaborate twig structures called bowers and decorate them with eye-catching bits of blue—everything from flowers and berries to bottle caps and pens. (Different species of bowerbirds build bowers with red and yellow accents.) Females inspect the bowers and decide which male to mate with based on which bower looks the nicest. 

2. Snails: nature’s cupids

Most land snails are hermaphroditic—each individual produces both eggs and sperm. Typically sperm transfer is reciprocal, so both partners give and receive sperm in the mating process. But their mating isn’t limited to insemination alone—some land snails do elaborate mating dances and even stab each other with tiny barbs called (no joke) “love darts.” These love darts are made of calcium carbonate, the same thing that shells and corals are made out of. You can see one in the picture—it's the little white bugle-shaped thing stuck to the snail on the left. Who knew snails were so kinky?

3. Mystery bones

These might just be the strangest bones in the animal kingdom—they’re penis bones, and scientists are still trying to figure out exactly why some animals have them and others (like us) don’t. These penis bones, or bacula, are from walruses, but lots of animals, including dogs, gorillas and chimps, rodents, and most bats, have them, and we don’t really know why. (Some female mammals have clitoral bones too.) Some hypotheses suggest that they function to support the penis; others claim they help keep closely-related species from interbreeding with each other, but we can’t be sure. It’s a mystery that scientists are still trying to solve.

4. Speaking of penises…

Snakes put us mammals to shame—they’ve got two. Their penises, called hemipenes, are tucked up inside the base of the tail. When a male snake mates, one hemipenis comes out of the body and is everted (think of how you can straighten out an inside-out sock by pulling on the toe by pulling it through the “body” of the sock—same general inside-out-turning process). Why have two penises? Each hemipenis is hooked up to one testis, so if after mating once, the snake finds another partner, he has a reserve of sperm so he can mate again.

5. Widow spiders: a date to die for

This Valentine’s Day, be grateful that you don’t have to cozy up to a widow spider. They get their name from the fact that the mating process is often fatal to males. Some species engage in sexual cannibalism, where the female eats the male after (or even during) the mating process; in other species, the female just ties up the male in her silk and leaves him for dead. It may be advantageous for the female to kill the male after mating because once he’s “served his purpose,” she can ensure that no other females get to mate with him, meaning that her offspring can have greater genetic variability than her competition's young. What’s in it for males, though? The most important thing for the male is to pass on his genes; even if mating kills him, it’s worth it. Plus, when males allow themselves to be eaten by their mates, they’re providing nutrition to the mothers, helping create healthier babies. Which is kind of sweet, when you think about it.

6. Corals wait til the mood and moon are right

Just when you thought that the cannibalistic spider mating rituals meant that love is dead, corals are here to redeem your faith in romance. Not only are no corals harmed during this process, but they wait to mate in the light of the full moon. Corals don’t have eyes, or even brains, but they can tell when the moon is full through genes that allow them to sense blue light reflecting off its surface. The blue light triggers the high point of the corals’ reproductive cycle, so they’re all ready to mate at the same time. When that happens, all the corals release sperm and eggs into the ocean to be carried by currents to their potential mates. It sounds…kind of messy, but it’s actually really beautiful.

7. Moonwalking manakins

Male Red-capped Manakins are the whole package—not only do they have colorful feathers to catch the eye of potential mates, but they can dance, too. Males set up shop on tree branches and rapidly shuffle from side to side in a kind of “moonwalk.” It’s so majestic that we’re having a hard time coming up with the words to describe it—just see for yourself.