This is earned for finding optional collectible #3. If missed on the first run, you can "Play Episodes" and select specific parts of the Episode in order to find the missing optional photos through
collectibles mode. The following collectible is described and can be seen in the video below at 2:28:
As you walk along the road in the desert, you'll pass by a billboard, and then notice an animal on your right side. As you approach, it runs away. Follow it to its den, and spot a skull on the ground nearby.
Getting all 6 collectibles in this episode will also reward you with the following: