Since my last two columns have focused on how cats communicate, this week I'd like to explore the ways dogs "talk" to each other. Just as humans can communicate with words or actions, dogs also tend to use their voice and body language to get their points across. Unlike us, however, dogs use their strong sense of smell to understand each other. (Of course, we use our sense of smell, too - just more subconsciously.)

The most common way for a dog to communicate with his doggy friends, or with the person standing in front of the treat jar, is to bark. Some breeds bark more than others, as any terrier owner can tell you.

But with the exception of the basenji, which "chortles," all dogs bark at least occasionally.

Sometimes it's an invitation to play, sometimes it's an attempt to get your attention and when it's directed at your postal carrier, it's Fido's way of saying, "Alert! Alert! Intruder on the premises!"

Another sound we all identify with dogs is growling. Dogs will sometimes play-growl, like when they are wrestling with each other or when involved in an intense game of tug-of-war with their owner.

But most of the time, a growl is fairly easy to interpret. It sounds just like the warning it is: "Come any closer and I'll bite."

Even if you couldn't hear your dog, you could still get a good idea of what he was trying to communicate just by watching him.

A dog that is happy and trying to get you (or a cute neighbor dog) to play, will jump around and play-bow - a classic canine move in which he lowers the front part of his body while sticking his rump in the air (yoga enthusiasts will know this position as "down dog").

A dog that is happy and playful will also usually have his mouth open and relaxed. That same dog, if he gets nervous or fearful, will close his mouth, freeze in place and if pushed, may snarl and show those big scary teeth in an attempt to intimidate whatever, or whoever, is threatening him.

A dog that wants to show he is submissive will get low to the ground to make himself look smaller, or even roll over to expose his belly. If he is very overwhelmed, he might even urinate a bit (puppies often do this when greeting their owners).

It's not good for your carpet, but it's a natural reaction for your overexcited pooch.

The final way dogs communicate with each other is through smell. Everyone has seen two strange dogs approach each other and immediately start sniffing each other's rear ends. They are inspecting scent glands located there, and it's perfectly normal dog behavior.

When dogs lift their leg on fire hydrants, trees or other "targets," they are leaving a message for the next dog to find. No one is sure how much information dogs can glean from these smells, but some experts believe they can "read" everything from the sex of the dog to what its last meal was with just a few sniffs. Clearly, when it comes to dogs, the nose knows.

Although we may not ever be able to understand everything our dogs are trying to tell us, if we pay close attention, we may be able to get a better idea of what their world is like.

To learn more about canine communication, consider these resources:. On Talking Terms With Dogs: Calming signals econd edition by Turid Rugaas (available in paperback or on DVD).

. Canine Body Language, a photographic guide by Brenda Aloff.