A sand martin male, though it’s not visually obvious FLPA/Alamy Stock Photo

Leave a good-looking corpse, and your mates may mate with it. That at least is what recently happened with sand martins in Japan, which were filmed engaging in homosexual necrophilia.

In 2014, Naoki Tomita and Yasuko Iwami from the Yamashina Institute for Ornithology in Abiko saw a dead sand martin by the roadside. As they watched, three males repeatedly mounted it. After 15 minutes, the researchers collected the body and later found it was a male (see video, below).

They have now published an article describing the incident – only the second paper describing such behaviour in birds.


Homosexual behaviour is common in birds, but in this case it was probably due to mistaken identity, as male and female sand martins look the same.

As for necrophilia, at least 30 cases have been reported in birds of all kinds. It is only when the body is collected that the sex of the dead bird can be confirmed, says Kees Moeliker of the Natural History Museum Rotterdam, the Netherlands. He published the first description of homosexual necrophilia in birds – a study made famous when he won one of the Ig Nobel prizes that honour “achievements that make people laugh, and then think” in 2003.

The Yamashina researchers think the event they witnessed occurred because the dead bird happened to end up in a pose resembling the female mating position. “We suggest that posture is an important trigger arousing male sex drive,” they write.

Moeliker, who has become something of an expert on necrophilia in animals since winning his Ig Nobel, agrees that the males were responding to the posture, rather than having a predilection for dead bodies. “It’s a mistake,” he says.

Davian behaviour, as mating with corpses is sometimes called, has now been observed in many kinds of animals, from spider mites to whales. While it may provide pleasure to some, it seems to have no benefit in terms of survival.

The only known exception is an Amazonian frog called Rhinella proboscidea, in which the females are often drowned by hordes of males during mating. The males continue regardless, squeezing the eggs out of the dead females’ bodies and fertilising them.

It is clear that animals engage in many kinds of sexual behaviour once regarded as “unnatural”, despite the reluctance of many biologists to report such behaviour.

Moeliker has reports of three other cases of homosexual necrophilia in birds, plus two in mammals and one in tortoises, but these have not been published. It was brave of the biologists in Japan to do so, he says.

But their paper is too similar to his to merit an Ignobel, according to Moeliker, who is now on the Ig Nobel committee.

Journal reference: Ornithological Science, DOI: 10.2326/osj.15.95