Dog sucks tail
You must of course make sure that there is nothing medically wrong with the dog. The tail is an extension of the dog's spinal column...so there could be a medical problem somewhere in the body and the tail sucking is the sign of the dog's illness. Sucking it may help relieve pain/anxiety. You need to see a vet first to rule this out. Have the vet check the dog's anal sacs too.
If it's not medical it could still be psychological - he could have some type of compulsive disorder and medication may help.
It could however just be a behavioural problem. The best way to deal with this is take detailed notes. WHEN is the dog doing this (while you're watching t.v., playing with the baby etc) WHAT do you do when you catch the dog (sooth the dog, scold the dog etc.) Some dogs suck/chase tails simply to get attention. If you think this is the case you may try rewarding NOT sucking. IGNORE the actual sucking.
If nothing helps ask you vet for a referral for a vet that SPECIALIZES in behaviour problems. In general these problems often require a bit of extra effort, because there are so many possible causes.....but they are solvable.
Julie Sansregret - AHT, Dog trainer
1313, rue PineRidge,
J7T 2M7 (450) 424-1469