Unusual and extreme

Some animals bend over backwards when courting their mates, like this brolga — a crane-like bird — in Queensland, Australia. (Image credit: Uwe Bergwitz/Shutterstock)

On Valentine's Day, lovers who are eager to woo their partners show their affection with traditional gifts of red roses, heart-shaped boxes of chocolates, or with romantic dinners at fancy restaurants. There's usually some effort involved, but pulling off a memorable Valentine's Day is easier — and generally safer — than some of the courtship rituals performed by other animal species.

For most animals, wooing comes with heightened personal risk. A male's showy displays, while attracting a female's attention, could also attract nearby predators, and fights between male rivals can also result in a date night with a body count. In some cases, winning a cannibalistic female's affections places the male at the top of the post-coital menu.

Many of the courting behaviors practiced by animals may seem strange to us, but as peculiar and risky as they are, they work just fine for their intended audiences. Here are a few examples of unusual and extreme courtship rituals in the animal kingdom.

Firing love darts

A Cornu aspersum snail that was hit in the head by a love-dart (arrow) so hard that the dart came out the other side of its head, next to the right eystalk. (Image credit: Monica Lodi & Joris M. Koene, Journal of Molluscan Studies (DOI: 10.1093/mollus/eyv046))

Look closely at these photos of land snail Cornu aspersum, and you'll see a small appendage close to the eyestalk. That tiny structure was propelled into the snail's head by its mate, delivering an infusion of a special mucus that prepares the snail for receiving an envelope full of sperm.

As land snails are hermaphrodites, either snail in a mating pair is capable of fertilizing the other, and both are equipped with "love darts" that they use to stab their partner — after they spend a bit of time circling around and touching each other with their muscular pseudopods.

Some snail species shoot single darts, some shoot multiple darts, and others use a single dart to repeatedly jab their mate for close to an hour, according to a 2006 study, published in the journal The American Naturalist.

Scraping and scratching

Reconstruction of theropods engaged in scrape ceremony display activity, based on trace fossil evidence from Colorado. (Image credit: Xing Lida and Yujiang Han)

Little is known about dinosaurs' mating habits, but evidence preserved in rocks in Colorado suggests that some dinosaurs practiced a ritual dance much like one performed by living birds.

Paleontologists found scrape marks — many dozens of them — in four sites that held remains of Cretaceous dinosaurs. In a 2016 study published in the journal Nature Scientific Reports, researchers explained that they saw distinct similarities between these scratches in the rock, and so-called "nest scrapes" created by certain types of male birds as part of their courtship displays.

Male birds across a number of ground nesting species — including sage grouse, puffins and various shore birds — scrape the ground in front of females, as if to demonstrate how good they would be at building a nest. They make dozens or even hundreds of scratches at a time, and usually accompany scraping with strutting, puffing themselves up, and fanning their tails.

Twerk or be eaten

A black widow female dwarfs her male counterpart. Male black widows can 'twerk,' as seen in new video of the spiders' mating dance. (Image credit: Sean McCann)

Black widow (Latrodectus Hesperus) females are about twice as large as males, so the smaller suitors have to take some precautions when approaching a female's web, lest they be mistaken for prey and eaten before mating even gets underway.

Males stay safe by announcing their presence to the female with vigorous rump shaking.

As a male steps onto a female's web, he vibrates his abdomen, sending signals coursing along the silk strands. He advances, vibrates and pauses, advances, vibrates and pauses — a pattern distinctly different from the shorter, more irregular movements of trapped prey, researchers found in a study, published in the journal Frontiers in Zoology. The study authors also discovered that the vibrations that males produce are at a low amplitude, further distinguishing them from prey movements, which were more dynamic and percussive.

Injecting sex hormones

Two Siphopteron sp. 1, caught in the act. (Image credit: © Johanna Werminghausen)

Hermaphroditic sea slugs possess both male and female sex organs, and when pairs come together to mate, they stab each other between the eyes with a needle-like appendage called a penile stylet, delivering a cocktail of prostate fluid. This tactic was described as "just weird" by a researcher who co-authored a 2013 study about the odd behavior, published in the journal Proceedings of the Royal Society B.

Scientists are uncertain as to why exactly the slugs target this body area for stabbing, but they suspect that the hormonal injection may serve to increase the possibility of successful fertilization.

Mystery circles

These 'mystery circles' are about 7 feet wide and are made by a 5 inch fish. (Image credit: Kawase et al)

"Mystery circles" on the ocean floor near Japan that measure about 7 feet (2.1 meters) in diameter were recently found to be made by a fish only 5 inches (12.7 centimeters) in length. The intricate symmetrical patterns were first noticed by divers in 1995, and in 2013 researchers described what created them: a species of pufferfish, with mating on its mind.

Males swim along the seafloor flapping their fins to sculpt the remarkably intricate ridges and valleys — a process that take seven to nine days — and then decorate them with shell fragments and sediment. After interested females are fertilized, they lay their eggs in the nest site at the center.

Though the structures are beautiful, scientists wrote in 2013 that the lines and shapes carved by the pufferfish serve to channel sediment particles, and likely don't serve an aesthetic purpose.

Built-in glow sticks

This jumping spider has UV-reflective body parts. (Image credit: Matthew L.M. Lim and Daiqin Li)

Body parts that reflect ultraviolet light help male jumping spiders in the Cosmophasis umbratica species catch females' eyes (all eight of them). Males lure the female spiders by striking poses that display these glowing patches prominently.

However, female C. umbratica spiders have a glowing trick of their own, possessing palps — a pair of appendages near the head — that fluoresce green in ultraviolet light, which they use to attract the males.

Both male and female spiders rely on these signals to tell who's in a mating mood, scientists discovered in a 2007 study published in the journal Science. When ultraviolet light was blocked and the spiders didn't glow, they lost interest in mating, the researchers found.

Tail whipping

The male Marvelous Spatuletail (Loddigesia mirabilis) sports a four-feathered tail that's twice the length of its body. (Image credit: Greg R. Homel)

In one species of hummingbird — the marvelous spatuletail (Loddigesia mirabilis) — males attract females by whipping their lengthy tails back and forth.

And those tails are impressive, two of the four feathers measure about 6 inches (15 centimeters) in length — about twice as long as the birds' bodies — and are tipped with shiny iridescent "paddles," which the males whirl feverishly at likely mates.

Illusion bachelor pads

The geometry of the courtship site creates an illusion of uniformity: When a female bowerbird views the court from within the avenue, all of the court objects appear to be the same size. (Image credit: L.A. Kelly)

Bowerbirds are known for building elaborate structures to attract female interest, even decorating their bowers with arrays of colored objects that appear to be selected and displayed for their aesthetic appeal.

But there's more to their arrangement than meets the eye. Researchers discovered that male bowerbirds construct their bachelor pads in such a way that when the male bird stands in front of it, he appears larger and more imposing to the female viewing him from outside.

And the birds that create the most successful illusions were the most popular with the females and the most likely to mate with them, scientists wrote in a 2012 study, published in the journal Proceedings for the National Academy of Sciences.

Ultrasonic love songs

(Image credit: Colin Robert Varndell/Shutterstock)

Male mice seeking to impress a mate sing unique high-pitched songs, vocalizing in the ultrasonic range. They produce these whistling sounds — which differ greatly from normal communication — by creating a type of feedback loop of airflow in the windpipe and larynx, according to a 2016 study published in the journal Current Biology. Scientists discovered the mechanism by shooting high-speed video of the mice's larynxes as they vocalized, capturing 100,000 frames per second.

Impressive though this technique may be, female mice are picky about which songs they like; they prefer tunes that differ from those sung by their relatives, according to an earlier study published in Feb. 2014 in the journal PLOS ONE.

Invisible tap dance

A male red-cheeked cordon-bleu songbird performs his mating 'tap dance' to court the gal next to him on their perch. (Image credit: Nao Ota.)

High-speed video recently revealed a mating dance performed by a species of songbird tapping their feet too quickly for the movements to be seen with the naked eye.

Blue-capped cordon-bleu songbirds (Uraeginthus cyanocephalus) — both males and females — were known to bob their heads and sing to each other during courtship, but a 2015 study published in the journal Scientific Reports was the first to capture the rapid tapping of their toes — and the birds tapped their feet faster if they were sharing the perch with a prospective mate, the scientists discovered.