Explanation: ambushed by a Spino
From Create Your Own Story
"So, I was eating some plants and I had no idea that I was being watched. He was observing me, trying to think of a way to catch me off-guard, and eventually he did find one. I was facing my back to him and he could see my bare asshole. He must have liked it a lot, to the point when he decided to charge head first into me."
"He threw me on the ground and quickly took out his penis, and before I could say anything he rammed it straing into my ass. I screamed in pain and started crying, but he ignored me.