Just guessing here, but those two pieces of crawdaddy pictured contain some edible meat.

I wonder why they were left behind. Maybe the animal in question was scared off before it could finish the meal.

Raccoons eat crawfish all the time.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."