Rabbits and hares are both prolific breeders. The females can conceive a second litter of offspring while still pregnant with the first. This phenomenon is known as superfetation. Lagomorphs mature sexually at an early age and can give birth to several litters a year (hence the sayings, "to breed like bunnies" or "multiply like rabbits"). It is therefore not surprising that rabbits and hares should become fertility symbols, or that their springtime mating antics should enter into Easter folklore.