that they’re chasing?
And if there is a conclusive answer to this, how was that answer arrived at?
Our family dog is half Shih-Tzu half Cocker Spaniel. His tail is long. Long enough, in fact, that he’ll nip at the tip of it when he has an itch. Presumably he knows that the tail is as much a part of him as, say, his ears which also get scratched.
As for the classic ‘chasing the tail’ act, I’ve seen Danny run around in quick, tight circles before, but it doesn’t really seem like he’s chasing his tail. My personal take is that he’s easily amused and would ride attractions that spin around a lot at amusement parks.
From what I’ve read, tail chasing results from overstimulation and boredom. While in the wild, young animals, such as dogs, will chase their own tails, as they grow and learn they quit doing that. It’s a waste of energy.
But in domestic situations, dogs and cats and such, don’t get enough exercise and they don’t have to worry about food or wasting energy. So they get overstimulated and for the moment forget it is their own tail.
They are just having so much fun running around, they overstimulate and next thing you know, they’re running around in circles while giving us quality material for YouTube.
My cats very rarely chase their tails, but they’ve done it. They also very regularly bathe themselves, including their tails, so they do seem to know that their tails are “part of them” in whatever sense they understand that.
When they chase them, I don’t think they’re unaware or forgetting that these are their tails; I think they’re intentionally pretending, for fun.
One of my cats, for instance, plays with toy mice. He doesn’t just chase them when we throw them - he also throws them around for himself. He’ll even place them behind a chair or around a corner, then go around to the other side and do the whole “spotting-readying-pouncing” routine, often repeatedly. It’s clear that he’s well aware that the mouse is not actually real, and it’s highly unlikey to me that he is just conveniently, constantly forgetting this fact. He’s just pretending.
My cat does that thing with the toy mouse, too. He will also do it with a real mouse, if the real mouse is not energetic enough.
The last live mouse he brought home was not going to go gently. The cat would set the mouse down, turn his back–the mouse would charge him. My cat actually sidestepped. He was very confused. This blew his little cat brain.
I think he must know that’s his tail. He chases it, he catches it, he decides it needs a little sprucing up so he licks it. Then he chases it some more. Sometimes he just lies there, twitches the tail, and watches it intently, like–should he bother to chase that thing?
I’ve seen our little cat, Jelly, spin around and around at the top of the cat tree, chasing his tail. He most definitely gets over-excited, as I’ve seen him “catch” it, bite it, and yelp, as he must have forgotten that it was still attached to his bottom! 
I’ve seen video of an adult lion chasing its tail. I’m pretty sure it was in a zoo, though, so boredom might still be a factor.
What Markxxx said. Excessive tail chasing is considered an abnormal repetitive behavior. From what I understand ARB’s are generally considered to be a result of frustration or boredom when obseved in (non-human) animals.
The Wiki page on stereotypy has some more info on the topic. I’m personally interested in this because our dog was a star gazer. It’s mostly under control now but she still has episodes on occasion if she’s overstimulated. I have a feeling she spent a lot of time crated or confined before we adopted her.
I’m familiar with dogs, but not this term. What is a “star gazer” in this context? Google didn’t help me.
troub there is a short clip in the dog section (near the bottom) of the page I linked. I am no expert in this, just an interested individual. It’s possible I’m using the term incorrectly.
I’m using the term to describe a dog that is excited by and compelled to follow lights or reflections projected above them. For example, my dog used to go bananas when we emptied the silverware from the dishwasher on a sunny morning.