I've been spending the past few days researching the sloth for my current project, so it is a very happy coincidence that this set of photos showed up: a new side to the sloths of Panama.
I am including Choloepus hoffmanni (one of the two-toed sloths) in my current research project because its genome was recently sequenced, and now I need to find out various life history traits about this species.
I have had a heck of a time discerning what their mating pattern and testis mass are, so I think I might email the people who took the pictures above to see if they have any estimates. Unlike a lot of mammals, but not completely unusual, sloths have internal testis that do not descend completely. This can make it more invasive to collect and measure testis mass.
They are pretty solitary species, like orangutans, which makes me inclined to think their mating pattern is monogamous (meaning only that a female mates with only one male during ovulation, not that they mate for life), but given the new picture evidence of how quickly they can move, it would be nice to confirm.