The animals you've met may not be able to add and subtract—or even talk—but you've probably witnessed behaviors that suggest real mental acrobatics.

We'd like to hear your stories of animals acting intelligently. Send us a tale plus a picture of your brainiac. We'll pick our favorites and publish them online.

There may never be another bird like Alex. The brainy African gray parrot, who died in September at age 31, had a grasp of numbers, colors, and even a very basic insight into the concept of 'zero' that challenged scientists' most fundamental assumptions about animal intelligence.

Comparative psychologist Irene Pepperberg of Brandeis University bought Alex at a pet store in 1977, and trained him up until his death. "He broke all preconceived notions of what it meant to be a 'birdbrain'," she wrote in an email. "He showed us to what extent birds can process information—at the same level as apes or dolphins or young children."

Pepperberg's next project with Alex would have involved optical illusions, "to determine if Alex literally saw the world the same way we do."

—Jennifer S. Holland

AlexFoundation.org