New born Red-tail Boa Constrictors (Boa constrictor constrictor) just one hour old. Boas give birth to live young as do 30% of the worlds snakes. Gestation is from four to eight months. Neonate Red-tails are about one foot long when they are born. The Bed-tail Boa is distributed from the Amazonian forests of Columbia to northern Argentina. It is very polymorphic and reaches an average size of six and a half to ten feet. The disposition of the red-tail boa and its beautiful coloration has made it a popular species in the pet trade and it is regularly bred in captivity.