When you use a statuette, you take on the health, experience, resistances, etc. of that animal. When you change back (by using the statuette again or waiting for the time limit to run out), your original stats should be restored. Different animals have different friendly / hostile relationships with various monsters.
When you transform back into yourself, there is a short delay before others' attitudes change around you. If you take the from of an animal friendly to a particular monster, walk up to them, transform back and attack immediately, you will loose reputation points for attacking a 'friendly' creature.
Kathy; There may be a bug if you die while still transforming. Did you try using the statuette again? BTW, the frog statuette is the best for speed.