Actually, I believed it in the cases of octopi, chameleons, squid, and fireflies before I actually saw it in all their cases with my own eyes (and I have seen them all do what they do), even though I don't fully understand the phenomenon. I've also seen dorado exhibit incredible color change/shimmering after being caught and hauled into a boat.
But I don't believe that a mammal can have glowing eyes (although I believe they can exhibit eye shine, which is reflected light), and I need to see glowing eyes in a mammal or read of it from a peer reviewed paper in order to believe it.