The Knowledge Dogs Protect Us From

I found out during spring yard cleaning. It was nerve wracking, but then I like creepy things. I also have a great first line of defense. Here's the background: I occasionally circle the tennis courts and bring home the unwanted escapees. Go to Petsmart and three tennis balls are at least $5. I'm cheap. As you might guess, freebies lead to abundance. My backyard was carpeted with the things. May geek that I am, I wanted to count them so I organized them. Woofie was immediately interested, but then she loves to play ball. (See Imminent Tennis Ball Seizure.) I think it was her careful examination of each ball that made me notice at all. I grabbed the camera because I thought it was funny that she was being so picky. Sorry the pictures are a little rough.

She started to "kill" the ball, common dog play. I caught a glimpse of something shiny on the ball and was worried it was a tack or a nail. As I got closer, I realized that my previous double quotes needed to be edited out.
She realized I saw and decided to let me in on her secret. She apparently killed it before it could camouflage to an actual tennis ball again. Here's a closeup:

I never knew. I realize now just how much she does to protect us and keep us from worrying. I wanted to celebrate her prowess:

Here are some previous kills I found once I knew what to look for. The last two pictures, I think, indicate a scalped mutant and in a separate location its oddly crusted brain.