Why are sloths so slow?” Vittorio Colonna recently asked us via Facebook. Sloths may be the slowpokes of Central and South American forests, but they are hardly the only animals that dawdle through life. So Saturday’s Weird Animal Question of the Week thought we’d look at some of the planet’s pokier animals and why, for them, slow and steady wins the evolutionary race.
Pacing themselves
The slowest mammals in the world, sloths, have a top speed of a mere mile (1.6 kilometers) per hour. Their biology makes them poke along at a rate that would get them honked at in traffic.
Sloths are “living on the edge of their energy budget,” Becky Cliffe, a zoologist at the Sloth Sanctuary of Costa Rica, says via email. They have a very slow metabolism and “every move has to be planned out.” The animals can’t even regulate their own body temperature, and that affects their digestion. Food takes an average of 16 days to pass through a sloth’s digestive system. But warmer weather helps that process go a little faster, Cliffe reported in a study published April 2 in Peerj. That lets sloths eat more when temperatures are higher.