Do Roosters Have Penises? How Did They Lose Them?

Owning chickens opens you up to a whole new world of questions. Like, for example, what comes first, the chicken or the egg? How do chickens mate? And do roosters have penises? Today, you are going to learn all about the naughty bits of your roosters, including whether they have a penis and how evolution caused chickens to lose them. Let’s get started.

Do Roosters Have Penises?

It may be shocking to find out that no, roosters do not have penises. Another shocking statistic for you is that 97 percent of all bird species lack a penis. Alarmingly, some birds do have penises, such as the duck with its infamous corkscrew. However, your rooster is without. What they do have is a reproductive organ known as a papilla.

The papilla is a small, fleshy protuberance that is located just inside the vent of the bird. During mating, the rooster “everts” the papilla, which is coated in sperm, into the cloaca of the hen. The sperm is then transferred to the hen’s oviduct, where fertilization takes place. More on this in a bit.

Do Roosters Have Testicles?

Roosters may have been short-changed by nature when it comes to their papilla, but they do have a pair of testicles. Rooster testicles are located inside their body, near the kidneys.

The size and appearance of rooster testicles can vary depending on the breed, age, and season. Generally, they are smaller than human testicles and are typically oval-shaped and whitish in color. During the breeding season, the testicles may enlarge due to increased hormonal activity.

While the basic function of rooster testicles is similar to that of human testicles, there are some differences in the way they function. Rooster testicles produce sperm continuously, unlike humans, whose testicles produce sperm intermittently.

Why Don’t Roosters Have Penises?

Many birds do not have penises, which has led researchers to ask why. What caused roosters to lose their penises? Turns out, there is an answer. See, during the beginning stages of development within the egg, the male chicken fetus has an external structure that seems capable of growing into a penis. Before hatching, however, this structure seems to vanish.

It has been hypothesized that this is caused by a mutation of a Bmp4 (bone morphogenetic protein). Various studies have found that Bmp4 has various functions. First, it is involved with the formation of cartilage and bone during the fetal stage. Bmp4 is also involved with a process known as programmed cell death, also called cellular suicide. In other words, Bmp4 kicks in around 9 days into a rooster’s development, causing their penis to revert and shrink into a papilla.

What would happen if Bmp4 was blocked? The beginnings of the rooster’s penis would continue to grow into something much like a mammalian penis.

Why Do Some Birds Have Penises and Others Don’t?

Now, you may be wondering, “Why do ducks have penises but roosters don’t?” The presence or absence of a penis in male birds is a complex evolutionary trait that has been shaped by a variety of factors. Some species of birds, such as ducks and ostriches, have evolved penises as a result of selective pressures related to sperm competition, which refers to the competition between sperm from multiple males to fertilize a female’s eggs. The longer and more complex the penis, the greater the chance of success in fertilization.

In contrast, most bird species, including chickens and other domesticated birds, have lost the ability to develop external genitalia, and instead, use a cloaca for both excretion and reproduction. This is believed to be an adaptation to reduce the risk of injury or infection associated with external genitalia.

It’s important to note that the absence of external genitalia in birds is not necessarily a disadvantage, as birds have evolved other mechanisms for successful reproduction, including internal fertilization and specialized reproductive organs such as the cloaca and papilla in male birds.

In short, some birds have penises while roosters and other birds do not because of various factors impacting survival, such as reproductive success and the environment.

How Do Roosters Use Their Papilla?

Rather than using penetration to ensure the continuation of the flock, a rooster and a hen kiss. No, it’s not the kind of kiss that involves two pairs of lips. The mating of chickens is complex and rather fascinating, as it involves more than mating. Here is a look at how a rooster not only attracts a willing hen but also mates.

Courtship

The courtship phase of mating begins when the rooster approaches the hen and begins to display a variety of physical and behavioral signals that indicate his interest in mating. These signals can include vocalizations, such as crowing and clucking, as well as physical displays, such as puffing up his feathers and spreading his wings.

If the hen is interested in the rooster, she will respond by assuming a submissive posture. This involves lowering the head and tail. The rooster will then know to approach. He may also make a few low rumbling sounds.

Mounting

The next stage is called mounting. This is when the rooster climbs onto the hen’s back and positions himself for the kiss. Mounting is usually quick. The rooster uses his wings for balance and stabilizes himself by grabbing onto the hen’s feathers.

Cloacal Kiss

As mentioned earlier, since roosters do not have penises but a fleshy protuberance known as a papilla, there is no penetration. To be technical, the cloacal kiss is when the rooster’s cloaca is brought into contact with the hen’s cloaca. When the papilla within the rooster’s cloaca is positioned, the transfer of sperm through the papilla begins.

In this video you can watch the previous three stages:

Semen Transfer

The rooster transfers semen to the hen’s reproductive tract through a series of rhythmic contractions of his cloacal sphincter muscle. These contractions help to ensure that the semen is deposited in the proper location within the hen’s reproductive tract, maximizing the chances of fertilization.

Fertilization

Once the sperm has reached the hen’s reproductive tract, they encounter and fertilize the ovum (or egg) that is released from the hen’s ovary. This process can take several hours or even days, as the sperm cells navigate the complex and highly regulated environment of the female reproductive tract.

Once fertilization occurs, the ovum begins to divide and develop, eventually forming an embryo that will hatch into a chick after approximately 21 days of incubation.

When Does a Rooster Start Mating?

Roosters can start mating with hens as early as four to five months of age. However, the age at which a rooster will begin mating can vary depending on factors such as breed, size, and environment. Some breeds may mature faster than others, and a rooster that is kept in a large flock may have more competition for mating opportunities, which can delay the onset of mating behavior.

Tips on Keeping Your Roosters Fertile

When you want little chicks running around, it is important to keep your roosters healthy. After all, reproduction requires a bit more than a cloacal kiss to make a chick — as you have seen. Here are some ways you can ensure that your roosters stay healthy and fertile:

Provide Your Roosters With Good Nutrition

Low fertility is often caused by poor nutrition. Make sure you are feeding your flock high quality chicken feed, as well as fruits and vegetables. Certain breeds also thrive when they have a chance to roam for their food. If your rooster tends to be restless when cooped up in the chicken run, consider expanding his territory.

Keep the Correct Number of Roosters

Did you know that roosters can die from mating excessively? This is why larger flocks need more than one rooster. If you have more than 10 hens, you may need 2 roosters to keep them from getting too stressed and tired.

Vaccinations

Even the most robust of roosters may face illness. Although roosters cannot get the same reproductive issues as hens, they are susceptible to infections such as avian infectious bronchitis, avian influenza, or mycoplasma. These infections can cause inflammation or blockages in the reproductive tract, leading to reduced fertility. Speak to your veterinarian about getting your rooster properly vaccinated for various diseases, especially those that may impact reproductive health.

Safe, Clean Shelter

Maintaining good hygiene in the coop and run is crucial for keeping roosters healthy and fertile. Regularly cleaning and disinfecting the coop can help prevent the spread of diseases that can impact fertility. And remember, you do not want your coop to be overcrowded either.

Overcrowding can lead to stress, aggression, and competition among roosters, which can negatively impact their fertility. Providing ample space for each rooster in the flock can reduce stress and promote good reproductive health.

Final Thoughts on Rooster Penises

Do roosters have penises? No, they have a papilla, located inside their multi-functional organ called a cloaca. During mating, the sperm is transferred to the hen through the cloaca during a process called a “cloacal kiss.” The reason why roosters don’t have a penis like many other birds is due to a combination of genetic mutations and evolutionary adaptations. So, next time your friends are over looking at your flock, wow them by saying that rooster reproductive anatomy is truly unique.