I just adopted my piggies today. They seem to scratch a lot (like dogs do with their hind legs). Is this normal? They don't do it constant but about once an hour or so. They also twitch sometimes and/or shake their heads like wet dogs do. This is my first time owning piggies so I'm not sure what all this means. The twitch may just be them popcorning. They do it while running around the cage. They haven't let me pick them up yet so I can't just search their fur for fleas. How can I tell if they have fleas or not?