I enjoyed Animal Body Fat Match so much that only after learning that my spirit animal is a slop hornet did I realize there is no privacy policy or even an identifiable creator.
Note: data may not be fully accurate, source list found through this youtube video
Nature's high score, at least in that list, is the army cutworm moth, at 72%. At the other end, crabs have less than 1% body fat. Among mammals, kangaroos are at 2%—an unrealistic fitness goal if ever there was one.