The nyala breeds throughout the year, but mating peaks in spring and autumn. The reason for this is still unknown, but attributed to the photoperiod and the feeding habits of the animal. Females reach sexual maturity at 11 to 12 months of age and males at 18 months (though they are socially immature until five years old). Once sexually mature, a male's seminiferous tubules begin spermatogenesis, that is, the generation of sperm. In a study, males over 14 months old showed active spermatogenesis.