(According to a publication in the journal Animal Behaviour, they can actually see you coming in slow motion. They process more visual information than we can, for example, your average housefly can see a light flickering at a rate nearly seven times faster than we can. So what we perceive as fast is in slow motion for them.
One of the researchers, Dr McNally compared it to the famous bullet-time scene in the Matrix where the bullets were moving at an incredibly slow rate as far as Keanu Reeves was concerned.)