Yeah, Males are really easy to tell. They will eventually have to straddle their "testicles" as they get bigger. Those things will just drag along behind them. I used to feed them dog food, but they will eventually get a protien rash that is really disgusting and bleeds a lot. But if your only going to keep him for a week or so, you should be fine. The protien problem is a long term problem and has no short term effects on them.
~Jim