My female will hiss at her tree for no good reason. I'll be working on the computer (her tank is near the wall behind the computer chair) and every now and then she'll let out a short, low hiss. Apperantly she's talking to herself as she's redecorating her enclosure herself, because the majority of the time when I notice her hissing, she's pushing the tree with her body to a different spot. She's never hissed at me while taking her out to handle her though.