"Hanging Out" by Laura Wolf;
used with permission under CC BY 2.0
Sloths generally attempt to reproduce once a year, but at times, they do not move enough in the course of a year to find a partner to mate with...
When a female sloth is, however, ready to mate, she will yell out what is called a "mating scream" to signal to any nearby males. This then signals time for the males to compete for the female; they do so by hanging from the tree by their feet and pawing at another until there is a winner.
This is all extremely hilarious and extremely true!