My juvenile Colombian BCI female is currently in a 4x2x1 PVC enclosure at 10 - 11 months of age (she is a giant for her age though, she is 3 ' and 8.49 " )

So, unless you get a fast growing female, you shouldn't need to get a big cage for awhile. But if you do get a female it will almost certainly need a 6x2x1 or similar cage EVENTUALLY.

The rule of thumb is that a cage must be at least half the length of the snake, so if you do get a female you can house her in various sized tubs until she gets over 4 foot, then you would need a 4x2x1 (or 4x2x2) until she reaches 8 foot

after 8 foot you would need to switch her to a 6x2x1 minimum


A male would need a lot less cage space for its entire life.

And, to answer your question on sizes between sexes, Females are usually 7 - 11 feet (although anything over 9 foot is huge, and 10 - 11 foot is monstrous)

Males are usually 5 - 7 foot long, maybe 8 but females are almost always much bigger.

And, we aren't even taking weight into account. Female colombian BCI boas can be anywhere from 15 - 60, and even upwards of 80 pounds! (again, the bigger the more rare it is)

Males are ofcourse a lot less bulky than females

Hope this info has helped!