Kangaroos mate by the male inserting its penis into the female's vaginal canals and ejaculating sperm. Kangaroos have two reproductive tracts, which lead into two separate wombs. The two vaginas are partially fused at the base, and both accept sperm during mating.
Kangaroos become sexually mature between 24 and 48 months old for males and 14 and 20 months old for females, depending on climate. Kangaroos living under arid conditions mature later. Females may enter estrus throughout the year. Females may also retain an embryo in one of their wombs until they are ready to continue the pregnancy; this is called embryonic diapause.
Males court females by sniffing their urine and stroking their tails. After mating, the male's semen forms a mucus plug inside the reproductive tracts. Gestation takes 33 days, and birth occurs through a third, median vagina that forms to allow passage of the newborn kangaroo, called a "joey."