There’s a lot that goes into dog body language, but one of the most important things to know is what mood your dog (or that strange dog) is in. If a dog is in a good mood, they’re not going to bite you. If a dog is in a bad mood, it’s time to avoid them! Just by knowing their mood you can get an idea of what to expect.
The simplest way to tell a friendly dog from an unfriendly dog is their spine. Their spine is the emotional center! When a dog has a stiff spine (and stiff, or tucked, tail) they are in a negative emotional state. They might be anxious, fearful, predatory, or aggressive — but it’s not good! When they have a wiggly/relaxed spine (or tail), they’re in a positive emotional state: happy, excited, peaceful, content, joyful.
Videos to demonstrate! (I’m leaving out a lot of body language that differentiates between “stressed,” “anxious,” “aggressive,” “happy,” “excited,” “playing,” and “content.” Just focus on positive vs negative!)
This dog has a wiggly, swishy tail. He’s in a good mood, even though he’s barking. When he hops up, he’s asking to play — his tail is still swishy!
This dog starts out kind of relaxed (wiggly), but as the video goes on gets more and more stiff. Even though he’s also barking, it’s no longer because he’s in a good mood. By 11 seconds, he’s anxious and afraid. (The owners are probably totally unaware of this. Most owners are):
The spine is part of the torso and neck, too, remember, so if the tail isn’t swishy but you’re getting lots of bendy neck and shoulder movements, they’re still relaxed! The chihuahua above turned his whole body: he was too stiff to turn just his head. This dog, though we can’t see much of the tail, has a relaxed spine: his head and shoulders turn without moving his whole body.
This dog is calm and in a good mood. Notice how his tail swishes a little as he walks, and his hips wiggle, too — like he’s walking in high heels!
Dogs that are calm but in a negative mood don’t swish. These dogs are using their predator side (negative emotional state) to shepherd animals, though the urge to attack or bite has been bred out of them. Forward to the 30 second mark, and you’ll see it:
Keep in mind that dog moods shift even faster than human moods do, sometimes, so what is happiness one moment might transmute to discomfort the next. That’s to be expected: roll with it, and you and your dog will get along a lot better!