Sloth

In this amusing and informative entry in Reaktion’s Animal series, Rauch (Dolphin), an English professor at the University of North Carolina at Charlotte, explores the behavior, anatomy, and evolution of sloths. He explains that the earliest sloths evolved from the ancestors of “primitive anteaters” 47 million years ago and gradually increased in size, giving rise to giant ground sloths that weighed 9,000 pounds and possessed fearsome claws that some paleontologists believe were used to skewer predators in self-defense. Modern sloths’ slowness, Rauch suggests, results from the low amount of protein in their leaf-heavy diet; to compensate, they preserve energy by maintaining a low body temperate (80 ºF) and “one of the slowest metabolisms of all mammals.” Examining how human perceptions of sloths have changed over time, Rauch notes that early modern European thinkers viewed sloths as “helpless and wretched” (in the words of 18th-century naturalist Thomas Bewick) and contends that industrial cultures’ focus on productivity and efficiency has spawned a fascination with the animals—in the form of memes and T-shirts bearing their likeness—as representatives of “an enviable lethargy and indolence.” This is chock-full of trivia (sloths have more neck vertebrae than most mammals, enabling them to turn their heads 270 degrees), and the copious photos of sloths in their natural habitat delight. Animal lovers will be entranced. Photos. (Jan.)