Roosters have internal testicles that produce sperm, but they lack an external penis. Instead, they have papillae that transfer sperm directly into the hen’s reproductive tract through a “cloaca kiss.” While less obvious than in mammals, roosters do possess the necessary male reproductive anatomy to fertilize eggs.
Roosters are an iconic symbol of the farm, known for their colorful plumage and loud crowing. But do these male chickens actually have reproductive organs like testicles?
The answer is yes – roosters do have testicles that produce sperm. However, their reproductive system is quite different from mammals.
Anatomy of a Rooster
Roosters have two testicles inside their body cavity near the backbone. The testicles vary in size depending on the rooster’s age, health, and time of year.
They are responsible for producing the male sex hormone testosterone and sperm cells.
During mating, roosters do not use a penis. Instead, they have two small bumps called papillae at the end of their reproductive tract that deliver sperm.
Let’s take a closer look at how rooster reproduction works.
Mating Without a Penis
Roosters and hens both have a cloaca, which is a single opening for waste elimination and reproduction. During mating, the rooster pushes out its papillae and presses them against the hen’s cloaca.
This allows the sperm to be transferred in a process called a “cloaca kiss.”
The sperm then travels up the oviduct inside the hen’s body to fertilize the egg before it gets laid. This is called internal fertilization.
Chickens evolved this unique form of mating because they do not have sex organs extending outside the body. In fact, both male and female chickens have a similar exterior appearance.
Why Roosters Don’t Need a Penis
Biologists theorize there are a few reasons chickens evolved without an external penis:
- Makes mating faster: The cloaca kiss takes just a few seconds. Fast mating is important for chickens that live in groups with a ranking order.
- Reduces risk of injury: An external sex organ could get damaged in encounters with other roosters.
- Eliminates unwanted mating: Roosters rely on cooperation from hens to successfully mate. Forced matings are rare.
Seasonal Size Changes
Rooster testicles are not permanently large like in most mammals. Their size changes depending on the season and testosterone levels.
In the spring and summer, longer daylight hours trigger increased testosterone. The testes grow bigger to produce more sperm for mating season.
In the fall and winter, less daylight causes lower testosterone and the testes shrink. The rooster produces less sperm during this time.
Why Hens Don’t Have Testicles
Female chickens have only one functioning ovary on their left side and do not have testicles.
The hen’s ovary contains all the ova (yolks) that will be released into the oviduct and potentially fertilized.
Since hens spend considerable energy producing and laying eggs, it makes evolutionary sense for them to have just one reproductive gland rather than two.
[Related Article: Why Do Roosters Crow At Night]
Rooster Reproductive Health
Like any other animal, roosters may occasionally experience health issues with their reproductive tract. Problems can include:
- Inflammation of the testes (orchitis)
- Blocked sperm ducts
- Low sperm production
- Testicular tumors
Rooster owners should monitor their birds for any changes and consult an avian vet if issues arise. Castration is sometimes performed to treat testicular problems or curb aggressive behavior.
The Fascinating Rooster Reproductive System
While roosters may seem very different from mammals, they have evolved a unique strategy for passing on their genes.
Next time you see a rooster, take a moment to appreciate the extraordinary biology behind their ability to crow and reproduce!