For World Animal Day, 10 Sharp Pictures of Brainy Animals

To celebrate World Animal Day, we take a look at the animal kingdom's brainiest creatures.

Humans may think of themselves as the sharpest tools in nature's toolshed, but as biologists have come to learn, the line between human and animal intelligence has become increasingly blurred.

To celebrate World Animal Day, we take a look back at the March 2008 cover story of National Geographic magazine and celebrate the remarkable—and distinctly non-human—ways that the animal world shows its smarts.