I avoid flying at night for the same reasons I avoid driving at night. Here in the hill country of Texas we have deer that love to come out at night and play on the roads and runways. I still drive and fly at night if I don't have a convenient alternative but I avoid it if I can. I've done low approaches over the runway to check or chase the deer off but they are so stupid that by the time I've come around the pattern to land they've returned to the runway. The other night driving home I counted around 30 deer on or near the roads for the last 5 miles of my drive home. A day doesn't go by where I don't see deer carcasses on the road and most of them get hit at night.