gerbil plucking his tail !

[hila]

help !! I don't know what to do , my gerbil bamba is constantly plucking hair from its tail , a part of it has become an ugly bone . I read on the FAQ's that it might be bored , but I don't understand why ... should I give them some more stuff to chew ? but what kind of stuff ? and there was a part there on the FAQ'S about dipping its tail in apple bitter , well I don't know what it is but are there any other suggestions for things to dip its tail in , so it wont touch it thank , hila