How Do Sloths Have Sex? It Begins With A Female Screaming In D Sharp

Not sure why you're laughing.


Rachael Funnell


Rachael Funnell

Digital Content Producer

Rachael is a writer and digital content producer at IFLScience with a Zoology degree from the University of Southampton, UK, and a nose for novelty animal stories.

Digital Content Producer

close up of a three-toed sloth in a tree

The intricacies of sloth sex can be surprisingly loud, violent, and speedy.

Image credit: Rob Jansen /

The cutest thing on Earth might just be a baby sloth, but how does it come to be? For an animal that’s famous for moving slowly through the canopy, it’s hard to imagine how they mate, but for three-toed sloths, it all begins with a female screaming in D sharp.

“Females will climb to the top of a tree when they’re in heat and scream for sex,” explained zoologist Lucy Cooke to 60 Minutes in a segment about the three-toed sloth, Bradypus. “But they scream in D Sharp.”


“I’ve seen Bradypuses having sex, it’s the only thing they do quickly. I was shocked, but then afterward, both male and female retreated and had the deepest snooze.”

As Cooke’s memorable impersonation demonstrates, D Sharp gets the job done in advertising the willingness of a female to mate. As for when the time is right, according to The Sloth Conservation Foundation, very little is known about mating seasons for these animals. In good conditions, females can come into heat monthly, but it’s possible there may be fertile periods that line up pregnancy with favorable environmental conditions.

Once a female sloth is in heat, she really puts the pedal to the metal. Her activity levels will skyrocket by 200 percent as she moves around, screaming in D and searching for an appendage of the same name. Her screaming frequency increases the longer she’s in heat, eventually resulting in a cacophony of noise that kicks off every 10 to 15 minutes.


The effort doesn’t fall on deaf ears, however, and males will respond with much excitement to the chorus of EEEEEHs. Sometimes the advertisement can work too well and multiple males flock to one female, resulting in fights.

It’s rare to see sloth copulation in the wild, but the lucky few who have borne witness have observed males mounting females both from behind and face-to-face, reports Live Science. It’s over quickly, sometimes in less than a minute, and the male will hang around for a few days to ward off any unwelcome suitors before heading off into the forest to potentially mate with another female.

Polygyny appears to be the mating strategy of three-toed sloths, in which the males will mate with multiple females. Males will go to a lot of effort to rid their territories of competitors, and most of the baby sloths sired each year will be sired by just one-quarter of the available males – and among them, there may be one who did most of the heavy lifting.

In a 2012 paper, scientists discovered that half of the baby sloths sampled were sired by a single male. And to him, we have just one thing to say.

On the topic of steamy animal news, did you know a low-flying chinook recently triggered a thousands-strong crocodile sex bonanza?

Did you know same-sex behaviour in animals has evolved multiple times for a good reason? Join us for our first-ever free virtual festival of science, CURIOUS Live, where we’ll be talking queerness in nature with science writer Josh Davis. Streaming online on October 21, 2023, we have 10 talks across three virtual festival "stages" on Life, Death, and Creation (y'know, the small stuff). Sign up now to find out more and secure your spot.


  • tag
  • sex,

  • animals,

  • mating,

  • reproduction,

  • sloth