Do Big Animals Always Sleep Standing Up?
Most large land herbivores can doze off on their feet, but only experience deep—or REM—sleep lying down.
"How do large animals like cows or buffalo stand up and sleep and not fall over or lay down?"
Mary Jo Tobin Edwards's question gives Weird Animal Question of the Week a chance to lay to rest notions about how some big mammals snooze. (Read "Secrets of Sleep" in National Geographic magazine.)
For starters, the idea that these animals only sleep on their feet isn't right.
Most four-legged land herbivores—cows, moose, rhinos, bison, and horses among them—can doze lightly on their feet, but they have to lie down to sleep deeply.
For instance, "when horses appear to be sleeping standing up, they can either be in a state of drowsiness or what is known as slow-wave sleep, which is