Well that was a sad way to start. Glad you were there & you decided to give him a chance. Its too bad that the owner just threw him away. Im sure it happens all the time though unfortunately. He looks like hes in good condition just keep on those mites & get those taken care of. Im kinda surprised he ate for you already but thats a good thing. Just make sure your temps & humidity are where they should be & he should do good.