I won't totally commit to it in terms of official canon, but my thinking for now is that yes, they can see it. The ear clips and the dragon's breath literally cause his eyes to glow (and other things, in certain GT endings :D). Remember though that the entire setting is a somewhat heightened, slightly cartoonish reality, so this isn't really out of place. The boars probably recognize the effect of dragon's breath. The hyenas would be able to work out he was under control, but would have no idea what the ear clips were. That product was a very...limited run.