Tail wagging is a good sign. It is, just as you suspected, scenting. The bigger concern with your story is that 400 grams on a male is pretty small. You need to remember it is not just about is he big enough to get the job done, but will he survive it? Males often go off feed when breeding. If your male is 1000 grams or more, not such a big deal because he has reserves. A 400 gram male is a different story. If he goes off feed he has much less to work with and depending on the duration of the fast, could spiral down pretty rapidly. It would be sad to loose a male on the first pairing. Just my $0.02