Congratulations, you’ve just clicked through to read a story about necrophilia. Let’s hope you’re not reading this on a public computer! 

I kid, of course. Despite the ick factor inherent in any talk about doing it with the dead, necrophilia really isn’t that big of a deal in the animal world. The act has been observed in everything from otters and sea lions to ducks and swallows. Lizards, frogs and snakes do it. So do humpback whales and crayfish.

But our necrophilic animal of the hour is the tegu (Salvator merianae). Thanks to an excellently titled paper – 'Corpse Bride Irresistible' – published in Herpetology Notes this January, this noble lizard now ranks among the rogues gallery of those who would copulate with a corpse. 

Over the course of two days, herpetologist Ivan Sazima watched the body of a recently deceased female tegu at an urban park in south-eastern Brazil. On the first day, a large male approached the female, gave her a few tongue-flicks, and then mounted and attempted to mate with her corpse for approximately five minutes.

Tegu Lizard Necrophilia 2015 03 13
Image: Ivan Sazima

The courtship might have lasted longer, Sazima noted, had the male not been disturbed by a group of geese (apparently proof that avian species beyond the chicken are capable of performing the 'cockblock').

On the second day, Sazima found the dead female had become bloated and “emitted a strong rotting smell". Blow flies and flesh flies now danced about her snout. But all of this was not enough to ward off yet another male hoping to get busy. In fact, this smaller male lingered for 49 minutes before calling it quits. 

It’s unlikely that these two male tegus were suffering from some sort of psychological imbalance. After all, death taboos are the provenance of humans. But it still doesn’t make sense that an animal would waste time and energy on an evolutionary, er, dead end. So what's going on here? 

Sazima says pheromones may be to blame. These chemical signals are secreted by animals for a range of purposes, and they play a large role in the love lives of lizards. Take some pheromones lingering on the female's body even after death, and the fact that female tegus are, as Sazima notes, pretty passive during courtship and copulation, and it’s possible that the males couldn’t tell the difference, in scent or behaviour, between a living and dead female.  

For most animals, necrophilia is a frustrating and fruitless affair. But there is one notable exception. 

Back in 2012, the Journal of Natural History published a paper under the title 'Functional necrophilia: A profitable anuran reproductive strategy?' Now, you may be wondering, how could necrophilia possibly serve a function? I’m so glad you asked.

“Now, you may be wondering, how could necrophilia possibly serve a function? I’m so glad you asked.”

For a small Amazonian frog, Rhinella proboscidea, mating occurs all at once in great orgiastic affairs on the forest floor. There are more males than females, so the guys jockey with each other for access. Before long, the leaf litter is writhing with hundreds of clumps of humping, pumping frog flesh.

Unfortunately for the females, this 'explosive breeding' can occur in and around puddles and ponds. In some instances, the weight of all those brutish males keeps the female below the water’s surface for so long that she drowns. By all accounts, it sounds like a horrible way to go.

Rhinella proboscidea necrophilia_2015_03_13
Image: Izzo et al, 2012. Journal of Natural History.

Just as with the tegu, some male frogs refused to leave the females alone even after death. The researchers observed one male “squeezing the sides of [the female’s] belly with rhythmic movements of his front and hind limbs”. But this was apparently more than a horny toad copping a feel – the squeezing actually expelled the female’s eggs, allowing the male to fertilise them externally just as he would if the female had been alive. 

“It is the first record of functional necrophilia in the world,” said Domingos Rodrigues, one of the authors of the paper.

Jose Padial, an assistant curator of amphibians at the Carnegie Museum of Natural History, put it another way: “I think these toads have fallen in an evolutionary trap triggered by selective pressures.” 

The average lifespan for these amphibians is about three years, which means if a female dies in her first mating season, the species loses out on thousands of potential tadpoles – even if a persistent male finagles a few eggs out in a last-ditch effort. 

“What intrigues me is how such a disastrous behaviour may have first emerged,” says Padial. “Perhaps some decline in females for some unknown reason triggered the origin of the behaviour, for only in a situation where females are extremely scarce could such stubbornness have some advantages for males.”

It’s like Ian Malcolm said all those years ago, “Life finds a way.” Sometimes, that way is death.  

Top header image: Christoph Anton Mitterer, Flickr