Pygmy three-toed sloths swim in the warm waters off the coast of Panama. They live exclusively on a tiny island nearby. They get from one tree to another by swimming, not crawling on the ground. Swimming is faster and easier for them. A researcher is studying these sloths. She fitted some of them with tiny high-tech backpacks that record all kinds of data. She is learning about their behavior, genetics, and biochemical processes. She wants to know how different from other sloths they are, and how similar. Are pygmy sloths a distinct species or just a smaller version of the slow-moving creatures?