Tail chasing is a very common behavior in an active
puppy. In an older dog, tail chasing may have
different and more serious causes. Here are some reasons that dogs chase their tails:
1. Because the tail is always there. Puppies don’t know where their bodies end and the world begins. So a wiggly little tail is definitely intriguing. This is especially true when the puppy has been separated from his littermates and has only himself to play with.
2. Older dogs sometimes chase their tails when they are anxious, bored, or frustrated.
3. Tail chasing can be a symptom of a physical problem such as the presence of fleas or irritated anal glands.
4. Tail chasing can also result when a dog is confined and has his movement restricted.
5. Some breeds such as Bull Terriers, German Shepherd Dogs, and Australian Cattle Dogs are more predisposed to chase their tails, suggesting that this tendency may be an inherited trait.
6. The dog may have canine compulsive disorder. This is a rare condition, but it might be the cause of tail chasing.
7. One good turn deserves another.
Source: Sandra and Harry Choron. Planet Dog, a doglopedia. Houghton Mifflin Co. 2005