I wish they gave a hint where to find the source material.

The Guardian, http://www.guardian.co.uk/environment/2010/jan/20/wolf-wildl..., has more content including this paragraph:

The organisers were alerted to suspicions about the image by Spanish photographers who recognised the wolf and the location as the Cañada Real wildlife park. Wolf experts also questioned why the wolf would jump the gate when a wild animal was more likely to squeeze between the bars.