Zacharias wanted to cringe away at the sound of the man's voice, not because it was particularly harsh but because he wasn't used to hearing human voices through overly sensitive ears. It was, to say the least, a shock. And while the sugar glider part of him could adjust to the noises, the human part of him still needed to reconcile some of the differences between being human and being a sugar glider. Although his ears were equipped to handle it, his brain found it to be a slight sensory overload. He was, most likely, over thinking it all, but he couldn't help it. It was still all so new to him that his brain took it all in and analysed it at every turn. Like the fact that this man looked very large compared to his current size. Seriously, were people normally that big, or was this bloke part giant? One thing he knew, however, was that he doubted he'd feel quite as short ever again, even if he were about average as a human.
He wasn't sure what he was supposed to. Part of him froze, while another part wanted to run. And another part of him let out an unfamiliar to him noise that he'd read was referred to as crabbing. Part of him knew that, logically, this man wasn't likely trying to hurt him. But there was still that instinctual side of the animal that didn't understand, that viewed him as a potential threat. And, well, Zacharias didn't know what would happen, and if the noise let the stranger know to back off, maybe he could get away and return to his human body before things got out of hand. Or before he was found out and reported for not yet registering with the Ministry (though he hoped they had some leniency about just when to register. After all, it'd be stupid to register if it were a fluke or if someone got stuck).