That grumpy turtle could be a common snapping turtle (Chelydra serpentina), which are known for having sassy attitudes when they feel threatened. But on the off-hand chance it isn't spewing anger in your direction, how can you figure out whether it's a snapping turtle for sure? Not every turtle strolling through your yard is a snapping turtle, however. The good news is that snapping turtles are hard to miss, and will most likely be one of two species: a common snapping turtle or an alligator snapping turtle. A regular turtle and snapping turtle are two very different beasts, and it's important to know how to tell one from the other before going anywhere near it.