You're at a friend's house and along comes her collie, Baby, wagging her tail. Good girl! You bend over to pat her and are rewarded with a growl. What went wrong?
"It is so important for people to realize that a wagging tail does not equal a dog that is friendly or wants to be petted," says E'Lise Christensen Bell, veterinarian and board certified veterinary behaviorist at Veterinary Behavior Consultations of NYC. "It can, but you are much better off looking at the entire dog. If there are stiffened muscles, dilated pupils, tense facial muscles, or ears pinned forward or back, these are signs that you should back off."
For help with figuring out what the tail wag means, look for the direction of the wag or at how fast his tail is moving. Studies show that dogs wag their tails to the right when they are happy and to the left when they are frightened.
If Baby wags her tail high and back and forth, she's in her "happy place". When she's just being plain nosy, she will keep her tail horizontal to the ground. When Baby's tail is tucked between her hind legs, she's either frightened or being submissive. When she's wagging it low, she's worried or feeling insecure about something.
Dogs wag their tails for other dogs, humans, and other animals like cats. But research shows that dogs don't wag their tails when they are alone because there is no need. Just as humans use smiles and body language as social cues in different situations, our canine friends do the same.
"Dogs are much better at reading each other's body language than we are," says Dr. Bell. "Dogs that are behaving appropriately in social systems use their bodies and tails to communicate with other dogs even as they are observing the tails and body position of other dogs. This helps them avoid unnecessary conflicts."
Dogs also wag their tails to spread their natural scent from their anal glands. Each dog has a scent that's unique to him or her. An "alpha" or dominant dog that carries his tail high will release more of his scent than a dog that carries his tail lower. Often, when we see a dog holding his tail between his legs, he's frightened and doesn't want to release his scent. This is his way of flying under the radar.
Since dogs haven't yet figured out a way to talk to their owners and their other animal cohorts, they have to use their bodies to communicate. The eyes, ears and body positions are a few clear indicators of how they feel. But wagging their tails is one of the most visible and well-known ways canines use to clue people and other animals in on exactly what's going on with them.