There are 2 main reasons for this; firstly milk snakes are not small reptiles and can easily grow to 1200mm in length. The majority of the subspecies never exceed 36 inches, with a few of the North American varieties, such as the Central Plains milk snake ( L. t. gentiles) and red milk snake ( L. t. syspila ), rarely exceeding 24 inches. Hatchling black milk snakes can be kept in commercial rack setups with shoebox-sized plastic boxes or small (about 5-gallon size) cages. The snake is nonvenomous and happens to be the largest known milk snake. They require a proportionate amount of space to live happily. Black Milk snake Mysterious Color Change However, most pet milk snakes in captivity only grow to an average length of 32 inches (81cm). The milk snake's vivarium should be at least 860mm (34") in length. Milk snakes can be surprisingly adept climbers in comparison to many other commonly-kept snakes, so a vivarium which provides a degree of height can also be beneficial. As a hatchling, it is either red, black, and white, or yellow in color. This means that a four foot milk snake will require a cage no less than 4 feet long by a foot wide at the bare minimum, though larger is of course better. Milk snakes aren’t natural snakes, but will still appreciate things they can climb on, so height isn’t of primary importance. The Black Milksnake is a large variety, growing to about 4 to 6 feet in length. The subspecies is known to be very hardy in captivity and can make excellent pets. It takes a milk snake 3 to 4 years to reach its full length. Provide some undertank heating for a warm area of about 78 degrees, and the rest of the cage can be 68 to 72 degrees. A typical 20-gallon tank is 30 inches from one end to the other, which is about two and a half feet long. Milk snakes can range in length between 14 and 69 inches (35 to 175cm) long depending on diet, subspecies, and genetics. That means it’s fine for any snake between two and three feet. Its color gradually changes, becoming covered with dark pigments until it has turned a blackish brown or entirely black. Black milk snake is a subspecies of milk snake found in Costa Rica and Panama.