When the dog is chasing tail is a very entertaining canine behavior.
Puppies are naturally curious and playful, and they love to explore with their mouths. When they see sight of their tail moving behind them, they don’t always know that it’s a part of them. As a puppy grows, it learns to ignore its tail, but may turn to it for entertainment when bored.
When an older dog chase its own tail, may be sending you a signal, indirectly, that it needs some interaction or some new toys to play with. If you see your adult dog chasing its tail, consider interrupting the behavior by offering some substitute activity. If your dog chase its tail constantly, you’re going to need to find some ways to keep your dog active and happy; take time for more walks and active play-sessions, or take your dog to the dog park for some canine social time.
For many dogs chasing their tail, it might be a matter of catching just the right glimpse of their tail that, for whatever reason, triggers this hardwired instinct; this seems like a good explanation for dogs who only occasionally chase their tails. Also, if you laugh or shower your dog with attention when it whirls, it is likely to do it over again.
If this behavior seems non-destructive, then there’s nothing to really worry about. A dog that seems to be chasing its tail with the intention of chewing on it, or that is attempting to gnaw at its back and may be experiencing irritation or discomfort; some causes of that can be: fleas, infection, irritated and glands, worms. You may catch your dog dragging its backside along the ground; this is an indication something is bothering your dog; have a look and see if you can find the problem (for example: may be something stuck to the fur); in that case a visit to the vet may also be in order.
Some dogs do develop a compulsive disorder that causes them to fixate on chasing their tail. In rare cases, this may need to be treated with medication. A dog that can’t be distracted from spin may have a compulsive disorder. You’ll need to work carefully with your vet or possibly a trainer to help your dog to unlearn this behavior.