Why do dogs bark?

Barking is far more common in domestic dogs than in wolves, which bark only rarely and briefly as a warning. Thousands of years of living alongside humans appear to have amplified barking, partly because people bred dogs as guards and alarms. Studies have shown that humans can often tell from recordings alone whether a bark signals aggression, playfulness or distress. Low, harsh barks tend to signal threat, while higher, more spaced barks tend to signal play or isolation. Excessive barking is usually linked to boredom, anxiety or reinforcement, because the dog learns barking gets a reaction.