Rat snakes are a large, polyphyletic, group of snakes from the Colubrid subfamily Colubrinae. Many species tend to be very skittish and sometimes aggressive but the genus is nonvenomous and bites are usually superficial. A variety of species like Elaphe guttata guttata are known for the ease with which they are tamed and are common in the pet trade. There is considerable variation between different types of rat snake but most are medium to large, rodent eating snakes. Previously most were assigned to the genus Elaphe but many have been since renamed. The validity of some genera is debatable but for the purpose of this article a more liberal taxonomic stance will be taken. Rat snakes have traditionally been divided into two groups, New World and Old World species.