Whether your intent is to breed rabbits or just to understand the animal better, it can be helpful to learn about a rabbit's reproductive system. Rabbits have a remarkable reproduction system, known for both speed and abundance.
Puberty comes quickly in rabbits, at around 4 months for females (does) and an average of 6 months for males (bucks). This age is variant among the different breeds. Sexual maturity and the ability to procreate in a doe is indicated by a congested, purplish vulva and the habit of rubbing her chin on objects. Bucks can procreate whenever they want once they reach maturity.
The female rabbit has a symmetrical uterine system, which allows for maximum pregnancies. The uterus is formed by two distinct horns, each of which possess their own cervix and ovaries. The rabbit vagina is visible, and can be described as relatively large and pliant for the animal's size.
The male rabbit is able to retract his reproductive organs into his abdomen. When exposed, a male rabbit has two long hairless scrotal sacs which contain the testes. The rabbit's penis is relatively small compared to the scrotal sacs.
Fertility and Ovulation
According to Anna Meredith, head of exotic animal services at the University of Edinburgh, female rabbits are reflux ovulaters, meaning their ovulation is triggered by the sexual act. They have no set heat cycles; a sexually mature female rabbit is considered fertile at all times, although certain preferable breeding cycles (vaginal inflammation and chin rubbing) do occur. The male rabbit is also considered constantly fertile.
Copulation is a very short affair for rabbits. Courting behaviors by the buck include sniffing and following the doe, as well as expelling quick bursts of urination onto her. These behaviors can last as few as 30 seconds before the sex act begins. The buck mounts the doe for quick vigorous intercourse. The act triggers ovulation in the female about nine hours later.