THE UPSIDE-DOWN BOOK OF SLOTHS

An engaging introduction to an animal family that’s found its niche in the slow lane.

There are six types of sloths living today, Shreeve writes, but many more used to roam the Americas—from ground sloths like the elephant-size Megatherium to the marine forager Thalassocnus. In this populous family gallery, various species extinct and otherwise pose in leafy settings, often looking up to make eye contact with viewers. The author surrounds their shaggy figures with specific details of their ranges, diet, distinctive characteristics, and (for the modern exemplars) unique physical adaptations for living in trees. Modern sloths’ leisurely ways turn out to be just the ticket, she explains, for an efficient, low-energy lifestyle and for avoiding the notice of predators. Considering they’ve survived for more than 40 million years, they can’t be quite the “slackers” their common moniker implies. Along with all the scientific grist, she also notes that while prehistoric sloths “weren’t all that cute,” modern ones are totally adorable, with babies “hardwired for hugging” and three-toed adults bearing “peaceful smiles” beneath bandit-like masks. “And now…it’s time for a sloth slumber party!” she concludes, beneath a final image of a smiling snoozer comfortably sacked out in a leafy bower.

Fetching and informative.