Yeah mine hissed a few times here and there up to about a year old. Only bit me during a feeding mode though. After a while he was puppy dog tame. I read somewhere years back that they fed their adults once a month. Due to a pattern of bird migrations on and off the island food was not always readily available. Hence they would have periods of natural fasting and their metabalism is much slower. So definatly dont stick the food to them hard. After 3yrs my male was about 33-35", so pretty small, but not an adult yet. Their ability to color change is really neat too. They can be a dark brown one min and a bluish silver the next. Very beautiful animals and very underrated.