People who get rabbits as companions tend to forget that nature created rabbits as a prey species. As a prey species, rabbits will keep producing litter after litter, in order to keep their species alive in the face of extremely high predation in the wild. This is an effective strategy in the wild, but for the domesticated pet rabbit, it is creating a situation of too many unwanted rabbits.
Rabbits reach sexual maturity between three and six months of age.
A rabbit differs from other mammals in that the female ovulates after being mounted by a male. This is called induced ovulation. This is the only time she produces an egg. This also means that after a rabbit has given birth, if the male is still present, she can and most likely will become pregnant within 24 hours of giving birth. Problems that can occur with rabbit pregnancies are magnified if the rabbit is young when she gives birth.