Female Sloths Attract Mates by Screaming Until a Male Appears
Female sloths keep their courtship simple. When they’re ready to mate, they let out a loud, unmistakable call that carries across the trees. It’s a sharp burst of sound that breaks the usual stillness of the forest and alerts any male nearby. The call isn’t dramatic, just direct, and the response it triggers is surprisingly quick. Males start moving toward the source, and the entire interaction begins with that one clear signal.
A Mating Signal
Female three-toed sloths use a very specific vocal cue when they enter heat, and once she starts, she keeps going. It creates a reliable signal that carries across the forest and lets males know she is ready to mate. They tend to follow a seasonal pattern with births clustered around the first months of the year.
The calls rarely fall flat. Males respond, often with enthusiasm, and that can create a temporary traffic jam in the canopy. Researchers in Brazil have recorded males moving directly toward the sound, and in areas with dense populations, more than one male may arrive, often leading to tension.
Home ranges add another layer. Three-toed males tend to hold smaller territories, while two-toed males can roam across much larger areas. Female ranges overlap several males of their species. This gives each female a menu of potential partners nearby and sets up the conditions for a loud reproductive season.
The Brief Moment When Mating Happens
For all the buildup, sloth mating sessions stay short. Observers have recorded both face-to-face and rear mounting, and the entire event can take a few minutes. A male may attempt another round soon after, and sometimes the pair stays in the same tree for a day before parting. The male often lingers long enough to discourage rivals, then drifts off to resume his solitary routine.
This quick timing doesn’t mean the process is random. Studies of three-toed sloths found that a small percentage of males father most of the offspring. In one genetic survey, half the juveniles sampled were linked to a single male. That pattern shows strong polygyny, where a few highly successful males secure multiple partners during the season. Two-toed sloths lean toward a different system with stronger female promiscuity, spreading paternity across more males.
Everything revolves around efficient communication. A female’s call cuts through the quiet canopy loud and quite distinct. Sloths move slowly and spend long hours still, so a sound that repeats every few minutes creates a reliable beacon.
It draws males without requiring chase behavior or elaborate timing. When her cycle ends, the forest goes quiet again, and life returns to the steady rhythm sloths are known for. For a creature famous for taking its time, the whole system runs with surprising efficiency once that unmistakable call rings out.