It's the most romantic day of the year, the day when most of us will attempt to woo our other halves with cards, flowers and gifts, or, if you're a white-fronted parrot, a swift vomit in your significant other's mouth.
Plenty of people have odd fetishes but perhaps none as weird as these. From penis-fencing to public defecation, here are the ten weirdest animal mating rituals.
These birds, native to Mexico and Central America, are able to imitate between 30 and 40 different sounds – but their skills lie in attracting mates.
After selecting a suitable partner, the parrots will lock beaks and "kiss", after which the male will vomit into the female's mouth.
Flatworms engage in a bizarre "penis fencing" ritual in order to mate, which effectively involves one stabbing the other with their penis until insemination takes place. Flatworms are hermaphroditic, meaning they have both male and female sexual organs, and they can take on either parental role depending on which one becomes inseminated. The act is appropriately named "traumatic insemination".
Red-sided garter snake
These snakes hibernate in the thousands and when it is time to wake up, they leave their den to mate. When a female appears, dozens of males will jump on her to form a mass mating ball. According to studies, some male snakes secrete the same pheromones as females, attracting other male snakes to mate with them.
Hippos mark their territory by leaving piles of dung around and using their tails to launch the faeces as far as it will go. When a male is around and a female is interested, she takes part in a "dung-showering" ritual – in which she raises out of the water and sprays faeces around her. This is referred to as "submissive defecation".
This tiny little marsupial has a body length of between four and five inches but is a lothario – until he kills himself from sex. In violent, frenzied encounters which last up to 12 hours, he mates with as many female as he can. The mouse-like creature has so much sex that his body disintegrates – he gets internal bleeding, his fur falls out and his immune system is no longer able to fight infection.
When on the hunt for a mate, the male red-capped manakin bird shuffles up and down branches to catch the attention of females.
Wilson's bird of paradise
Perhaps a less weird ritual, but still amazing - and perhaps something humans could learn from. The brightly-coloured Wilson's bird-of-paradise is a cleaning freak and he has a habit of tidying up a patch of forest floor so his luminous feathers stand out to passing females.
The second largest slug species in the world has a problem – their penises are too big. As their members are nearly the same size as them, a banana slug has to choose a mating partner of around the same size (they are hermaphrodites). If it doesn't choose carefully, the penis can get stuck during mating. The answer? To chew off the slug's penis.
Female anglerfish dwarf their male counterparts, who barely look like the same species. When it comes to mating, a male will bite onto the female, then fuse his face to her body. He spends the rest of his days stuck to the female, releasing sperm when she releases eggs.
The lowly honey bee also has a rough time when it comes to mating. During the mating flight, male bees (drones) are selected to mate with the queen bee. After the deed is done, the end of the bee's penis is ripped off and his testicles explode. Even if he survives the act, he is still ejected from the hive because his sole purpose is to mate with the queen bee.