I know nothing about Sloths, so have no idea what the yellow colour on the back signifies (in terms of species or sex) if anything. We had rented a car for 6 weeks to explore Panama and primarily to go birding, and towards the end of the trip, in the vicinity of Colon, along a little-used dirt track/road, we saw this one crossing in front of us, painfully slowly. On the ground it looked ungainly and vulnerable, but once it reached a tree and climbed it looked more at home and eventually it grasped a branch with all four legs and hung there. This was the only sloth seen, and was very exciting!
Digitized from an old slide.