“That [reindeer] also avoid [power lines] during the day, when UV light is everywhere, is puzzling, and it isn’t clear why they should want to avoid the discharges anyway.” (http://www.nature.com/news/why-reindeer-steer-clear-of-power-lines-1.14868)
Perhaps for the same reason humans put signs on pylons: danger of death.
Ecomical 
Interesting