In the natural world, the end game of any individual animal is to reproduce and pass its genes on to the next generation. This genetic passing-on is what makes "survival of the fittest" work and is what fuels evolution. Animals that are able to survive long enough to successfully mate and pass on their genes ensure that the species, and those genes, persist into the future. Those that can't reproduce fall by the evolutionary wayside.
The pressure to reproduce is intense, so it's no surprise that some species have evolved some pretty drastic ways of ensuring reproductive success.
Take the tiny mammals known as "marsupial mice" (even though they are not rodents or related to mice), seen below. There are ten species, all native to Australia. These tiny carnivorous creatures have evolved an annual frenzied mating behavior that leaves the females bitten and bruised and every single male dead from sex-induced exhaustion.
Photo by Michael Sale via Flickr Creative Commons.
Rachel Sullivan of ABC science explains:
"Males live for exactly eleven-and-a-half months, dying from stress-induced immune system breakdown about two weeks after mating. Females, especially from larger species, may live longer, with around 30 to 50 per cent raising two litters, while only ten per cent of females from smaller species live long enough to breed again....
...All females come into oestrus at the time, triggering a mating frenzy among males. Copulation is a violent affair with males biting the backs of the females' necks during their brief encounter before each moves on to other partners. A fortnight later, every male is dead, overwhelmed by the stress-related corticosteroids produced during the frenzy of mating."
Read the rest of the story of these fascinating, sex-crazed animals here.
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