Two cuttlefish cuddle at the Georgia Aquarium in Georgia, U.S.
Credit: Wikimedia
1. The big display
Strategy: Flaunt it
Animals have developed bizarre mating behaviours simply because, at some point, they were tried and they worked. "If you survive really well but no one mates with you, your genes won't get passed on to the next generation," says Marlene Zuk, behavioural ecologist and animal mating expert from the University of California, Riverside.
This is why some animals have developed plumage that's a downright burden, such as the enormous ornamental tails of birds of paradise and peacocks, which help them catch the eye of potential mates, but hinder them from flying and escaping predation. Many characteristics evolved through sexual selection, which can be detrimental from a natural selection standpoint, "meaning that the trait hinders survival but aids in mating," explains Zuk.
2. Desperate husbands
Strategy: Fight for it
Part of understanding evolution is that it's not just about survival of the fittest, but about continuing the species. For the individual, reproduction can be a hard sell. Male bedbugs use traumatic insemination to impale the hard body cavity of a female wherever they can. His sperm swims around inside her until it finds and fertilises her eggs. Male Dawson's burrowing bees, on the other hand, may have to fight to the death for the opportunity to spawn offspring, killing hundreds of rival males in order to mate with a female.
3. Faking it
Strategy: Be a good liar
Pretending to be something you're not is a common strategy in the mating game. Small cuttlefish males, called sneakers, change colour and behaviour to mimic females and sneak past bigger males, thus gaining an edge over their larger competition.
It's not just males who fake it: female brown trout (Salmo trutta) often pretend to release their eggs by vigorously shaking their bodies next to undesirable mates. The male then ejaculates prematurely into the water, leaving the female free to find a more suitable male to fertilise her eggs.
4. Sexual cannibalism
Strategy: Take your partner to dinner
Eating a mate or an offspring is a common strategy in many species. Female black widow spiders often like to make tasty snacks out of their post-coital partners, but if they do this regularly, the architectural and chemical make-up of their web can change. The web can then act as a warning signal to wary males. "This reduces courtship towards the starved females that attack males more often," says Chad Johnson, a behavioural ecologist at Arizona State University in Phoenix, Arizona.
A 2010 Nature study found male gulf pipefish, which favour reedy habitats around Central and South America, prefer to mate with larger females. In pipefish, females compete for male attention then mate with them in a dance-like entwining embrace. The males carry the eggs and will abort batches from smaller partners by starving or cannibalising the embryos to make room for more appealing offspring.
5. Swapping sexes
Strategy: Be flexible
The ability to change sex depending on age, size, environmental conditions or gender balance creates reproductive flexibility. Many species of fish, such as the reef-dwelling parrotfish, are born female and change into males as needed. Starting out female is advantageous because female parrotfish are larger than males, so adult sex change means the older males will be able to mate with even the largest females. Other species, such as whiptail lizards, forgo a second gender entirely, maintaining their genetic diversity by having twice as many chromosomes as similar species that reproduce sexually.
6. Sex exchange
Strategy: Be available
Among bonobos, sex is readily used in exchange for food or to avoid conflict, often with relatives as well as friends. Sexual encounters, including mutual masturbations, oral sex and penis fencing, occur once an hour (in captivity) on average. Prostitution in the animal world isn't restricted to primates. Female Adelie penguins trade nest-building pebbles for sex, similar to male macaque monkeys who 'pay' females for sex by grooming them. In both cases, lower numbers of females lead to higher 'prices'.
7. Sexual parasites
Strategy: Be persistent
The male spoon worm is more than 1,000 times smaller than the female and, on reaching sexual maturity, crawls inside her uterus, where she keeps scores of other husbands. Male anglerfish are also permanent parasitic mates that bite a female and physically fuse into her body. The male then loses his organs inside his mate and connects to her bloodstream, effectively morphing into a hanging sperm sac. "Latching onto a female and having a part in fertilising her eggs forever will leave him with more offspring," Zuk says. As Darwin once said, "those who learned to collaborate and improvise most effectively have prevailed."
sex
Then there is the species that uses EM to send out messages,...sometimes called Internet Dating