This morning, the third and final Prized Pig is live: Meet Boss Hog
At Bronze Mastery level - collecting 3 Boss Hogs, you'll earn a nice defensive armor piece called the Jointed Panel, with 33/60 stats
At Silver Mastery level (collect 5 more pigs), the Jointed Panel's stats go up to 38/72.
Haven't gotten to Gold as of this post, but Boss Hog - like his predecessors, requires you to collect the same 3/5/10 of him to master each level.
It appears that once you've achieved Gold Mastery on Boss Hog, you'll earn a nice vehicle with impressive 100/128 stats, as the "Grand Prize" of this challenge.
You have all weekend to track down the last few Curly Tails, Fresh Shanks, and Boss Hogs you need to get Gold Mastery on each one (18 of each pig).