A black snake is typically one of several different species of snakes found across the world, in various countries and usually labeled according to its coloration. While not a scientific name for any species of snake, different regions will usually use the term to refer to different types of snakes that are common in that region. In the United States (US), the term black snake usually refers to either the black rat snake or the black racer, and in Australia it may be used as a shortened name for the red-bellied black snake that is commonly found throughout the eastern portion of the country.
The most common usage of black snake in the US typically refers to the black rat snake, also called the pilot snake. This is a non-venomous snake that is a type of constrictor and is typically found in mountainous areas in North America. As with other types of rat snake, black rat snakes usually feed on mice, rats, and other small rodents and are not usually aggressive toward people and other larger animals. When startled, they will sometimes rapidly vibrate their tales among dead leaves to mimic the sounds of a rattlesnake and will usually flee rather than attack a larger animal or person.
Another common usage of black snake in the US refers to the black racer, which is similar in color and appearance to the black rat snake, but with only a white chin and a mostly dark underbelly. While both black rat snakes and black racers are black in color with lighter undersides, the black racer is more distinctly black with less coloration than black rat snakes typically have. Young black racers, however, are lighter in color and are usually light brown before aging and darkening into a more striking black coloration. While black rat snakes are more likely to freeze and remain still when approached, black racers tend to quickly flee. They may also bite, though they are not venomous, if cornered or stepped upon.
The red-bellied black snake of Australia, however, is quite venomous and extreme care should be taken if approaching this type of black snake. Quite common in Eastern Australia, this snake can often be found by unwary hikers along waterways such as rivers, or lying beneath rocks and fallen timber. Though they are not especially aggressive and will usually flee when approached, they will strike if threatened or unable to flee. While there are no known deaths from this snake, their venom is still quite toxic and emergency care should be sought immediately by anyone who has been bitten.