How many times have you taken the dog on a camping trip? Each dog we've taken camping over the years has been a little nervous the first few times out. Eventually, they get used to it and relax. A lab we used to have took several trips before he'd eat the first (or even second) day, and for a lab, that's something! Some dogs are more sensitive than others and you just have to be patient. A healthy dog won't starve him/herself. I wouldn't make a big deal out of it, or you'll confirm his anxiety and possibly make it worse.