Squeal

Jake Huntsman created the WISH program in order to rehabilitate the broken and the misguided—to reshape young lives before they are hardened and ruined. Deep in the Hoh Rainforest, his wards are forced to reevaluate the world around them, and the values they embody.
But this time, the WISH trip to redemption is interrupted by a monstrous force—a rabid, feral hog, bred to be destroyed, intent on devouring the skeletal team of leaders and seven deadly teens, one by one.

Amazon.com link: http://www.amazon.com/dp/B00L3R1NQY
Amazon.co.uk link: http://www.amazon.co.uk/dp/B00L3R1NQY