Dolphins’ Circular Logic

Ordinarily, I’m quick to rush out to and quickly dash urban legends upon the rocks of reason. (Sound familiar, Whit?) But what sounded too silly to be true actually pans out this time…

Back in one of my previous dolphin trivia posts, I mentioned that dolphins only sleep with one half of their brains at a time. And when sleeping, they continuously swim in lazy circles.

Research published by Paul Manger & Guinevere Stafne at the University of Witwatersrand in South Africa has revealed that, during this sleep time, dolphins in the northern hemisphere (north of the Equator) swim in predominantly counter-clockwise circles, whereas dolphins in the southern hemisphere swim in clockwise circles.

Manger & Stafne theorize that this dolphin behavior is caused by the Coriolis force — an effect of Earth’s rotation that produces large-scale currents in the ocean and atmosphere — which is often (falsely) credited for water spinning down a drain in different directions in the northern and southern hemispheres.