These photos are currently the topic of much conversation within the British cryptozoological community and show a large black animal wandering around Britain's Dartmoor - an area noted for a wealth of high-strangeness, including the supernatural Whisht Hound.
Personally, I'm inclined to think they show a big dog.
In picture one, the animal looks to almost have a boar-like face, and a neck that is not at all dog-like. In picture three, it seems to have a cat-like gait (some have suggested a bear-like walk, too). Whereas picture six looks very dog-like.
Note the text that accompanies the photos where the writer addresses the nature of the shape-shifting whatever-it-is. Is it merely a large dog out for a stroll around the moors? Could it be one of the ghostly devil dogs of old England?
Note: The link above is to the Fortean Times website, and you may have to log-in to view the images.