Too cold for flies. Think they just like to flick their tails.
As for the hay throwing, I know in horses, they learn all types of vices when stalled too much. Cribbing, biting their tongue, flapping their lips, swaying, etc. It's neurotic behavior due to stress. I think some of the behavior we notice with the giraffes is also stress, boredom related.
I noticed lights are off already tonight. And we wait and see!