A dog’s bark may sound like nothing but noise, but it encodes important information. In 2005, scientists showed that people can tell whether a dog is lonely, happy, or aggressive just by listening to his bark. Now, the same group has shown that dogs themselves distinguish between the barks of pooches they’re familiar with and the barks of strangers and respond differently to each. The team tested pet dogs’ reactions to barks by playing back recorded barks of a familiar and unfamiliar dog. The recordings were made in two different settings: when the pooch was alone, and when he was barking at a stranger at his home’s fence. When the test dogs heard a strange dog barking, they stayed closer to and for a longer period of time at their home’s gate than when they heard the bark of a familiar dog. But when they heard an unknown and lonely dog barking, they stayed close to their house and away from the gate, the team reports this month in Applied Animal Behaviour Science. They also moved closer toward their house when they heard a familiar dog’s barks, and they barked more often in response to a strange dog barking. Dogs, the scientists conclude from this first study of pet dogs barking in their natural environment (their owners’ homes), do indeed pay attention to and glean detailed information from their fellows’ barks.