10 Worst Adaptations in the Animal Kingdom

Sloth Stomach
Are you calling me lazy? Cut me some slack. I just have some digestive quirks. iStock/Thinkstock

As far as quality of life goes, you'd think a sloth has it made. About 10 hours of sleep (more in captivity), a diet of healthy greenery, a side of bark and a life in the trees [source: Briggs]. What could be so bad?

Unfortunately, the sloth's low-key existence also leads to some complications. One is that a sloth's diet isn't that nutritious, so they need a big stomach with several chambers to hold a lot of food at once. Sloths can take an entire month to digest one meal, and they have to live a seemingly lazy lifestyle so they don't divert any energy needed to live [source: National Aviary].

Sloths also have a really low body temperature, but it can't get too low. If it does, the bacteria in the sloth's gut that digest food will stop working. That means that even if the sloth had just eaten enough food to fill its belly for a month, it can starve to death because the food will just sit there, undigested [source: National Aviary]. It's gotta be one of the worst -- and the most ironic -- of all the animal adaptations around.