I think criminalizing hitting an animal is a terrible idea. Pedestrians, other drivers, and cyclists can be unpredictable, but more often than not they are within a certain range of expected behavior. Not so with animals.

Driving late evening, with high beams on, no one else on the straight road, and right around the speed limit, I came upon a large herd of deer. I slowed down and kept a close eye on them. A small group decided to go from standing to running literally as I was passing them, and one grazed my right rear door with its butt as it did a 180 next to my car. They are not predictable and no amount of attention would prevent that.

That's not mentioning the small animals that can be very hard to see.