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The Scientists Who Watch Animals Have Sex

One researcher launched his career after diligently documenting a mallard duck fucking another dead duck.

Tortoises doing their thing. Photo via Wikimedia Commons

There's a TV show in the Netherlands called Vroege Vogels (or "Early Birds"), which has for years provided a weekly round-up of nature sightings in the country. For the most part, it's pretty tame, family-friendly entertainment. But in a segment this March, the show featured a goldcrest—Europe's tiniest bird—fucking another goldcrest. Oh, and the other bird was dead.

This alone would have been shocking. But even weirder, Vroege Vogels actually had a go-to specialist on the subject, who they called on to examine the footage. His name is Kees Moeliker.


"The program makers called me on a Saturday morning at breakfast and said, 'You'll be interested in this!'" Moeliker told VICE. "I was thrilled to see it. I immediately confirmed this was a clear case of avian necrophilia."

Moeliker's "expertise" dates back to 1995 when one day, in his office as director of Rotterdam's Natural History Museum, he saw a mallard duck fly headlong into the glass building. The bird fell to the ground. Moments later, a second mallard, began mating the dead animal where it lay.

Moeliker got a pen and paper and began documenting the ass-fucking for the next hour and a quarter until common decency compelled him to intervene.

Kees "The Duck Guy" Moeliker in Rotterdam's Natural History Museum. Photo via Wikimedia Commons

The resulting 2001 paper—"The first case of homosexual necrophilia in the mallard Anas platyrhynchos"—made little impact until it was spotted by the organizers of Harvard's Ig Nobel Awards for improbable research. The Ig Nobels are a parody of the Nobels with prizes given out for achievements that "first make people laugh, and then make them think." (Last year's recipients included a scientist who subjected himself to bee stings on 25 different locations of his body, to determine which would be most painful. This year's awards will be presented later this month.)

Moeliker won an Ig Nobel in 2003, which led to a flood of media attention, a TED talk, and a reputation as the de facto world specialist on animal necrophilia.

"After that, people started sending me their observations—and since nobody else was studying these behaviors, I became the expert. In the land of the blind, the one-eyed man is king!"


Moeliker's files now contain about 60 reliably documented cases of animal necrophilia involving 41 species of birds, mammals, reptiles, and amphibians, as well as what Moeliker says is the only known case of "osteophilia," a tortoise that was seen humping an empty shell in Azerbaijan in 2014.

But his findings are only the tip of the iceberg as far as freaky animal sex goes. Besides necrophilia, lots of other paraphilias have been noted in the wild. Zoophilia, or inter-species sex, has been observed between Antarctic fur seals and king penguins, and between dolphins and porpoises (in both cases against the will of the smaller animal). Many primates are known to practice incest, and female greater horseshoe bats share sex partners with their moms. Bonobo chimps, who seem to use sex as a kind of social glue, do it pretty much every way you can. And behind every case of weird animal sex, there's a researcher diligently watching it happen.

It's only in the last couple of decades that these divergent sexual behaviors in animals have come under the microscope of mainstream science. Before, it happened, but it was pretty hushed up. Moeliker, for example, put off writing his duck paper for six years because "when I looked in the academic record there were no references to this behavior."

Indeed, while scientists had been documenting animal necrophilia for at least a century, their research was rarely published. When it was, it was published in such a way as to deliberately slip under the radar.


For example, American ornithologist Robert W. Dickerman wrote a 1960 paper in the Journal of Mammalogy based on his observation of homosexual necrophilia in two ground squirrels. Afraid his paper would be rejected if he described the act outright, Dickerman coined the euphemism "Davian behaviour" for what was taking place.

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Another challenge in documenting and analyzing animal sex behaviors is withholding human judgment. For example, bonobos' pleasure principle extends to include behaviors we, as humans, would categorize as incest and pedophilia. And it's known that male orangutans regularly force copulation on females, which is hard not to see as rape.

The temptation to look at nature through the prism of our own values is both tempting and rewarding, said Harriet Ritvo, a natural history professor at MIT, "because nature is like the Bible: You can find anything you want in there."

She offered the example of 1950s primatologists studying baboon societies. "They used the fact that there were dominant males who have a harem as an argument to support conventional power dynamics within families and gender roles and so on," she told VICE.

But a couple of decades later, when a team of women primatologists studied those same baboons, they discovered that "if you look at the females and not the males, there's a female hierarchy that's more important," Ritvo said. "It depends who's doing the looking and where you look."


Even if we can accept that the animal kingdom is as sexually diverse as human society, it's impossible for us to say with any certainty what any of these behaviors mean without knowing the animals intentions.

"There are problems with applying those terms to people in the sense that you draw boundaries and establish categories that may seem firmer than they actually are," said Ritvo. "But if you think that animals have less self-consciousness than people do, then one of the questions you have to ask yourself is: Are you sure you know what the animals have in mind? Animals have a much more restrictive expressive range than humans and just because it looks like something else does it mean the same thing."

For his part, Moeliker is quite sure his mallard duck was no necrophiliac.

"It has to be a dramatic death, the animal must have died in the same position it would be in for copulation, and it has to be a recent death because there have to be hormones around the body," he said. "It's not the same as human necrophiliacs who are after sex with a non-struggling, non-responsive body and are often serial killers. I've not found any ducks like that."

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