There generally are not specific criminal laws regarding hitting a dog or other pet with a car and fleeing, as there are with people. But you may be cited for animal cruelty or for ignoring property damage notification obligations for failure to report hitting a pet in some states.
Penalties for accidentally hitting a pet with a car depend on the breadth of state animal cruelty laws, which are based either on intentional acts or failure to act on behalf of an animal, as well as on state hit and run statutes and the definition of property. The California Vehicle Code, for example, provides that failure to report damage to property after an accident is a misdemeanor, and pets are -- in another statute -- defined as property.
According to some reports, there are a million animals killed on American roads every single day, so let's look at what you should do if you find one.