Get a gang of crows together and it's a murder. Perhaps then, it is not so surprising that individual crows can occasionally be spotted engaging in certain unsavory habits from time to time. Namely, shagging their dead.
We already know that crows display unusual behavior around corpses. They hold so-called "funerals", a practice that mostly involves a great deal of gathering, squawking, and flapping, and has more to do with recognizing potential threats than it does with grieving for the dead. Now, thanks to a study recently published in the journal Philosophical Transactions B, we also know they can be partial to a bit of necrophilia (or should that be ne-crow-philia?)
Kaeli Swift, a PhD student at the School of Environmental and Forest Sciences at the University of Washington, first noticed this strange activity in 2015, while she was filming a crow funeral. As she explains on her blog, Corvid Research, a crow strutted up to the corpse before it mounted the body and started thrusting. One crew member asked if the crow was attempting some kind of CPR maneuver. Cute, but no.
This single observation led to a 3-year-long study, whereby Swift would place a corpse of a taxidermied adult crow, juvenile crow, pigeon, or squirrel next to a pair of mating crows and wait to see their reaction.
"In all, I tested 309 individual pairs of crows; or in other words, once again I freaked out a lot of Seattle residents wondering why there was a woman with a camera, binoculars, and some dead animals loitering in front of their house for long periods of time," she explained.
In the vast majority of cases, the crows would caw from a distance or dive-bomb the corpse – as you might expect them to if they perceive a dead crow as a sign of danger. The researchers also noticed crows would more often approach the pigeons and the squirrels, animals they are more likely to eat.
But occasionally, things turned frisky. In 24 percent of cases, a crow would approach another crow's corpse and start pecking, touching, pulling, and/or dragging the corpse. Roughly 4 percent of the time, the crow would attempt to have sex with the corpse.
"In the most dramatic examples, a crow would approach the dead crow while alarm calling, copulate with it, be joined in the sexual frenzy by its presumed mate, and then rip it into absolute shreds," Swift added.
To make sure the crows weren't confusing the dead bodies for living birds, the team performed a second experiment using a dead crow and a life-like crow mount. The birds responded to the "life-like" crow as if it was an intruder. And in contrast to the obviously dead crows, when they attempted to mate with the "life-like" crow, they did so without the accompanying alarm calls. So no, they were not mistaking the dead crow for one that is alive.
The researchers do not know why this happens but they have their suspicions. Curiously, the behavior is more common during the breeding season.
"What we think happens is that during the breeding season, some birds simply can’t mediate a stimulus (the dead crow) that triggers different behaviors, so instead they respond with all of them," Swift explained.
"This may be because the crow is less experienced, or more aggressive, or has some neurological issue with suppressing inappropriate responses."