Reflect on this: What do animals see when they look into a mirror?

Our Weird Animal Question of the Week came to us from @iscavenger, who tweeted us after reading our January column "Why Do Dogs Watch—and React to—TV?" She asked about domestic dogs' responses to mirrors, noting that some seem bothered by or stare at the looking glass.

For one, though dogs can recognize other animals or dogs in mirrors, they can't see themselves. (Take National Geographic's dog quiz.)

"Dogs are very intelligent and adaptable creatures who, like countless others, lack the cognitive development necessary to self-recognize visually, whether in a mirror, on a video, or in a photo," Liz Stelow, an animal behavior clinician at the Veterinary Medical Teaching Hospital of the University of California, Davis, said by email.

Studies that have tested whether dogs could use mirrors as tools to find food or their owners had mixed results.

It's not too surprising: Dogs evolved to communicate through scent, and smell is "more important for dogs than a visual recognition of 'self,'" Stelow noted.

Mirror, Mirror ... in the Pool?

What's more, self-recognition is not easy, noted Diana Reiss, an animal psychologist at Hunter College in New York and author of The Dolphin in the Mirror.

"It takes a good deal of sophisticated integration of information about yourself and your own movements and what you're seeing in front of you in that glass," Reiss said.

That's why it takes human babies 18 to 24 months to catch on to what they're seeing in the mirror.

Amazingly, some animals have also cracked the code: Dolphins, elephants, magpies, and some great apes know they're looking at themselves in the mirror.

Animals that show mirror self-recognition will often go through phases of discovery. One phase is what Reiss calls "the Groucho stage," in which animals repeat odd movements as they "seem to figure out that their behavior and the behavior of that guy in the mirror is related."

In the last stage, many animals seem to just want to explore their hard-to-see body parts—a result Reiss has seen firsthand in her research on captive Asian elephants and bottlenose dolphins. (See "Elephant Makes a Stool—First Known Aha Moment for Species.")

For instance, study dolphins would orient themselves repeatedly from different angles in front of the mirror to see marks that researchers had made on their bodies.

"They kind of did a double take," each time showing interest in examining the mark, said Reiss, who has received funding from the National Geographic Society's Committee for Research and Exploration.

The Asian elephants that Reiss studied would stand in front of mirrors and touch their tongue to the glass and examine the inside of their mouths, she said. "It's really remarkable."

Safety in Numbers

Even if an animal can't see itself in the looking glass, some "appear to recognize another of their species in the mirror [and] therefore turn to the mirror for companionship," said Stenlow.

Some zoos have used mirrors to trigger mating and nest building among flamingos, which breed only when they perceive their colonies are of a certain size, she said.

Mirrors placed in a particular way can also reduce the anxiety of horses, according to Horse and Hound magazine.

Tell us: Have you noticed an animal reacting to a mirror?