A Rooster’s Reproduction System
Biology of the Chicken, Part 4
Reading Time: 4 minutes
By Thomas L. Fuller, New York
In the previous article I discussed the reproductive system of our hen, Henrietta. As we continue our discussion of chicken reproduction I would like to introduce you to Hank, short for Henry. Hank is our male counterpart to Henrietta. Hank will be our “go to guy” as we refer and illustrate the male reproductive system of the chicken.
The chicken has evolved a unique system to ensure fertility and survival as a prey species. The male reproductive system of the chicken or rooster is much simpler than that of the female, or hen. Regardless of its simplicity, it is an equal partner in the genetic make up of the offspring. The chicken reproductive system is heterosexual, that is, requiring both male and female to contribute half of the genetic material for an offspring or chick. Hank contributes his half of the make up by way of the sperm produced in the testis. Henrietta contributes not only the single ovum from her ovary, but also the means of development within an egg.
Chickens, as in all birds, have a very special design for the male’s reproductive organs. Unlike mammalian males, Hank’s entire reproductive system is encompassed inside his body cavity. Sperm generated in the avian system are viable at body temperature. The body temperature of mammals is too warm for sperm, therefore reproductive organs are found outside the body.
Hank has two testis located high in the abdominal cavity in front of the kidneys near the backbone. These gonads (testis) tend to be bean shaped and shrink and grow on a regular basis influenced by seasonal mating. It is worth noting that mating increases with the increase in light hours. In the testis both sperm and male hormones are produced. Hormones such as testosterone influence traits like aggression, comb growth, spurs, and length of tail feathers. Though our Hank will continue to produce sperm for many years his quality of sperm will decline with age. Unlike Henrietta who is born with all the ova she will ever form into an egg, Hank must produce sperm regularly from the time he matures. A mature rooster, with good nutrition, genetics, and environment could produce as many as 35,000 sperm each second of his mature life. This is why you only need one rooster to 10 hens to ensure fertility.
The sperm leave the testis by way of the deferent ducts. These ducts are tubes that are narrow as they leave the testis and widen before they reach the cloaca. The widened area of the deferent tubes serves to store sperm for multiple matings and allows for sperm maturity. It takes from one to four days for the sperm to travel from the testis to the end of the ducts.
Each deferent duct opens into a small “bump” or papilla on the back wall of the cloaca. This is the mating organ. As a result chickens do not have penises. You may recall from Henrietta, the multi-purpose cloaca precedes the vent where the ends of the digestive and reproductive systems meet. Here is where hens and roosters excrete waste. This is also where in hen’s eggs emerge and where roosters transfer sperm for fertilization during mating.
As previously discussed, our feathered friends are evolutionarily programmed as a prey species. In reproduction, as it is in digestion, the systems need to include a certain efficiency and quickness for survival. This is also true of the mating process. When a rooster mates there is a short display of dominance. He then climbs on the back of the hen, places a foot on each wing, forcing the tail feathers upwards to press their cloacas together in what is called a “cloacal kiss.” In these few seconds sperm is transferred from the male cloaca to the cloaca of the hen. As brief an encounter as this is, it is efficient and effective. Henrietta, our hen, has sperm host glands built into her reproductive tract. These host glands can store sperm for 10 days to two weeks.
As we mentioned in the beginning of this article, a chicken’s sperm remains viable at body temperature. The action of laying an egg contracts these glands to force viable sperm into the oviduct far enough to fertilize the future eggs. Early poultrymen would buy their hens fertilized and have enough fertile eggs to set and not deal with a rooster.
As I have mentioned before, you do not need the presence of a rooster to get or continue to produce eggs. Unfortunately, Hank has nothing to do with egg production. If anything, his presence tends to lessen egg production due to stress on the hens from mating. You do, however, need the presence of a male for fertile eggs and chicks. Fertility is affected by both male and female. In both, fertility tends to decrease as chickens age. As Hank ages and starts to lose interest and ability to mate due to size, fertility will decrease.
The male reproductive system of the chicken is much simpler that that of the female. Hank only has one purpose in this heterosexual means of reproduction, fertilization. He does however procure considerable risk as a prey animal. Hank telegraphs his availability to mate not only to the hens of the area, but also the predators. His position is given away with a resounding crow, and his brilliant feathers and comb make him conspicuous to all. He may avoid having chick-raising responsibilities or nest chores, but as a prey species, he must do his job quickly and efficiently to ensure the survival of his kind.
Thomas Fuller is a retired biology teacher and lifelong poultry owner. Look for the next part in his series on the biology of a chicken in the next Backyard Poultry.