Generally, because they are happy to be getting attention or seeing someone who is good to them
Why Do Dogs Wag Their Tail?
Sometimes dogs wags there when they are happy
Dogs can wag their tails when they are happy or also when they are meeting new people. Dogs use there tails to show they are happy or excited.
We always like to think that dogs wag their tail because they are happy, pleased and being friendly. However, this may not be the full story. Dogs have actually been known to bite people whilst still wagging their tail, so they can't always be happy and friendly whilst wagging their tail.
Some theories think that the dog wags its tail because in 'dog language' it is saying 'You are superior to me in the pack and I mean no harm': but again this doesn't account for biting.
Another popular theory is that the dog is actually in conflict and the tail wagging in and out symbolises a 'should I stay or should I go' conflict within the dog. This theory doesn't sit comfortably with those who want to believe that dogs wag their tail through happiness.
Perhaps the least contentious view is that the dog is actually releasing excess energy, so instead of running half a mile, it squeezes the excess energy out of its tail. It is most likely to do this if it feels comfortable and generally ok, but occasionally it may feel aggressive and bite, even when its tail is wagging.
Some theories think that the dog wags its tail because in 'dog language' it is saying 'You are superior to me in the pack and I mean no harm': but again this doesn't account for biting.
Another popular theory is that the dog is actually in conflict and the tail wagging in and out symbolises a 'should I stay or should I go' conflict within the dog. This theory doesn't sit comfortably with those who want to believe that dogs wag their tail through happiness.
Perhaps the least contentious view is that the dog is actually releasing excess energy, so instead of running half a mile, it squeezes the excess energy out of its tail. It is most likely to do this if it feels comfortable and generally ok, but occasionally it may feel aggressive and bite, even when its tail is wagging.