The females are polyestrous, which means that they are capable of conceiving multiple times a year, which is a reason why they do not appear to have a breeding season. However, there does appear to be a peak in conceptions during the two rainy seasons of the year. Generally, the female conceives after two or three matings. Although the female has plenty of room in her uterus to gestate twins, twins are rarely conceived. The female African forest elephant's pregnancy lasts 22 months. Based on the maturity, fertility, and gestation rates, African forest elephants have the capabilities of increasing the species' population size by 5% annually under ideal conditions.