tangerine gecko

Question
i own a tangerine gecko which is only abput a year old he has been extremly healthy since ive bought him but recently i noticed some sort of black crust on the tip of his tail i went to the pet store and the recommended i put poly derm on it so it would help with the discomfort the next day i woke up to about an inch off the tip of his tail is completly dead looking and not fat like it used to be i have never owned a gecko or any kind of retptile is there somthing i did wrong or is this happen all the time.oh yah and my gecko has been acting very unusual he has bite me 4 times everytime i pick him up he runs away and bites me. can you give me advice because i am LOST!!....

Answer
Phil, I'm gonna give this one a shot.  However, please know it has been a long time since I have kept Leopard geckos.  It sounds like your lizard "pinched" the tip of his tail and it is now dead.  It is probably painful, and that may be why he is acting badly.  You could be very cautious and take him to the vet, but leopard gecko tails are designed to "drop-off."  It's a defensive adaptation they have.  So I would think that eventually the broken piece will dry up and fall off w/o further complications.  However, if his apetite declines or he starts losing weight/loooking bad call the vet immediately.