[andai]

I recently walked through a park at night, and noticed that the deer were still up and about. Then I noticed that all along the enclosure there were bright white street lamps. It struck me then, how inconsiderate this was for the deer.

[pavelrub]

Deer are mostly crepuscular and other than that more active during night time than day time. What you saw likely has little to do with the street lamps.

[andai]

Sure, but when are they exposed to darkness? When there's a power outage, which hasn't happened within my lifetime.

I'm pretty sure if I had to live with lamps shining on my face all night it would disrupt my circadian rhythm, regardless of when I naturally prefer to sleep.

[pavelrub]

The point is that deer being active at night isn't an indication of street lamps disrupting their ciradian rhythm. It's possible that those street lamps do affect it, but the behavior you saw isn't evidence of that.