Is "professional photographers don't have the right to claim ownership over expensively set-up and finished work if an animal presses the shutter button" really an important principle of freedom of information worth fighting for?
Or is it more of a complicated case that may possibly be winnable through an arcane technicality in the US legal system, but even if successful would probably be less useful to the average Wikipedia-user than the equivalent amount spent on cleaning up existing copyright-free content. Nice as the image is, more useful and interesting stuff gets deleted from Wikipedia every day.