When breeding season rolls around, foxes tend to get a bit mouthy – and what comes out sounds eerily human. This is what the fox says: a high-pitched "YAAGGAGHH" rivalled only by the screams of the almighty marmot. 

Chances are you've seen this clip pop up on social media this week, but it was actually filmed back in 2010 by Ki Steiner. And despite what many commenters have suggested, this is not attempt by the fox to call its canine best friend for some more playtime. 

The screech in the video is known as a "vixen's cry", and you'll hear it most often around springtime, when foxes are out luring mates. It's also used later in the season when unwanted visitors need to be chased away from young kits. And it's not just females doing the screaming, though scientists are still trying to work out why male foxes also use the call from time to time.

"This fox lives near our house and has interacted with our dog quite a bit," Steiner explained. "But this was definitely the craziest encounter we have seen between them. We now regularly hear that crazy bird-like scream the fox makes." 

The most likely explanation is that Steiner's dog simply got too close to the vixen's den, but it's also possible that the fox was on its own mate-finding mission when the two animals crossed paths.

The call is certainly blood-curdling enough that it regularly causes alarm. And it's not hard to understand why:

"The first time I heard a fox scream, I thought it was being attacked and called the police," says UK local Martha Louise Ryder, who has had foxes denning under her property for nearly two decades. "I felt like a complete numpty."

Strange as it may be, a bark or cry is far from the most peculiar sound you'll hear from a fox. The animals are highly territorial and have a whole repertoire of noises for aggressive encounters. One of the most common is "gekkering", a clickety-clack call and response that sounds more bird than mammal: 

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Top header image: John Ryan, Flickr