The belly of the northern black racer is bluish-gray, and the chin and throat are white. A bluish variety of racer, called the blue racer, is found between the Great Lakes and the Ohio River. A mottled variety of racer found in Louisiana is known as the buttermilk snake. Racers live chiefly in the eastern United States. Varieties found west of the Mississippi Valley have tan to olive coloration on their backs.
Racers often climb trees to reach birds' nests, and eat the eggs and young birds.
They also eat insects, frogs, small mammals such as mice, and other snakes. Some people believe racers kill large rattlesnakes, but racers never attack other snakes of their own size. When cornered, they defend themselves by biting. But they prefer to run away. Racers are members of the common snake family, Colubridae.