sierraclub.org - sierra magazine - july/august 2011 - whales - whales: the sea's mysterious giants
Photography by Flip Nicklin/Minden Pictures, from Among Giants | Captions by Della Watson
Sperm whales have the lowest reproductive rate of all mammals—they're able to give birth to a single calf every four to six years at their reproductive peak—and the largest brain of any living creature on the planet. These highly social animals often raise their young communally.