Mating is a deadly business for these females, as the males are so desperate to breed they don't care if the females get killed in the process

Nature is never a good place to look for moral guidance. Anything goes, as long as it increases the chances of one's genes being passed down the generations. Take the male Amazonian frog Rhinella proboscidea - it doesn't even care whether its mates are alive or dead.

Like many amphibians, the species is an explosive breeder. Males gather in huge numbers at spawning sites during the brief, desperate mating season, battling among themselves for access to females.

• Frog breeding behaviour: How frogs mate and produce spawn

Some females inevitably perish in the scrum, yet they are still fair game: by mounting a dead partner and then massaging her abdomen with his legs, a male can squeeze out her cargo of eggs and fertilise them in the usual way.

It's the only known example of necrophilia having an evolutionary advantage - to both the male and the unfortunate female, who would otherwise have missed out on breeding entirely

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