Animal researchers have no universally accepted scale of interspecies IQ. That's because each creature, from the lowly field mouse to the majestic bald eagle, has evolved a specific skill set that makes comparisons hard. Who's to say that a cat's knack for automatically mapping its environment is “smarter” than a pigeon's talent for solving math problems?
Our human opinion of what constitutes a keen intellect also makes ranking animals problematic. “When 'intelligent' behavior is language or tool use or abstract thought, humans trump every other critter out there,” says Laurie Santos, the director of Yale's Comparative Cognition Laboratory.