Why Do Male Dogs Have So Many Nipples

Why So Many Nipples?

Have you ever noticed that male dogs have rows of nipples lining their underside? It may seem strange at first glance. Unlike female dogs, male dogs obviously don’t need to nurse puppies. So why do male dogs have nipples too? In this article, we’ll explore the biology behind the purpose of canine nipples and why male dogs have so many of them.

Anatomy 101

All mammals, both male and female, have mammary glands that produce milk to feed their young. The biological function of nipples in mammals is to deliver milk from the mammary glands to the mouth of the offspring. According to the Mammary Gland article on Wikipedia, “Mammary glands are specialized milk-producing glands that develop on the ventral surface of mammals during gestation or around the time of birth. They are unique to mammals and essential for the nourishment of offspring.”

The mammary glands connect to the nipples through a series of ducts. When the offspring suckles on the nipple, it stimulates the release of oxytocin which causes the mammary glands to contract and eject milk through the ducts to the nipple. This allows the milk to be delivered and consumed by the offspring for nourishment and growth.

Nipples in Male Dogs

Yes, male dogs do have nipples, just like female dogs. According to the American Kennel Club, both male and female dogs have mammary glands and nipples that extend from their groin area up their stomachs. The nipples are a characteristic feature of mammals, and serve an important purpose in females for nursing young. So even though they do not serve a function in males, the nipples are still present.

Male dog nipples look similar to female nipples, though they are generally smaller. You may notice small bumps or protrusions in two rows extending from the dog’s groin area up the belly. The nipples are often pigmented differently than the surrounding skin. It’s perfectly normal for male dogs to have nipples, so there is no need for concern if you notice them.

Why So Many?

Dogs have multiple pairs of nipples because they belong to a litter-bearing species. According to the American Kennel Club, the average litter size for dogs is 6-10 puppies [1]. Therefore, female dogs need enough nipples to be able to nurse a large litter. While the number of nipples can vary by breed, most female dogs have between 6 to 10 nipples [2].

All dogs, both male and female, initially develop the same number of mammary glands and nipples in utero [3]. For female puppies, these mammary glands will develop further at puberty under the influence of hormones like estrogen. For males, they remain undeveloped. This is why male dogs have nipples too – they originally developed the same mammary system as females before sexual differentiation occurred during development.

So in summary, dogs have multiple pairs of nipples to accommodate large litters. The number is predetermined early in fetal development, before the sex of the puppy is established.


Male dogs have nipples for the same biological reasons female dogs have them – as a leftover from fetal development in the womb. All mammal embryos initially develop nipples in utero, regardless of whether they will be male or female. Nipples form early in pregnancy before hormones and chromosomes determine the baby’s sex.

According to Found Animals, having nipples provides no real evolutionary advantage for male dogs. However, losing the nipples through evolution would provide no advantage either. Over generations, male nipples have persisted as a residual trait from their time in the womb.

While male nipples serve no functional purpose, they also do not negatively impact the dog’s health or survival. This vestigial feature was not selected against during canine evolution. Since the presence of male nipples confers neither harm nor benefit, natural selection has maintained them as a neutral trait in dogs.

Puppy Development

Nipples play a crucial role in feeding newborn puppies. Puppies are born blind and deaf, relying completely on their mother’s care. They nurse every 1-2 hours for the first couple of weeks, getting vital colostrum and nutrients from the mother’s milk through her nipples.

According to the Austin Animal Center’s Foster Care Manual, “Puppies should nurse vigorously and compete for nipples. Newborns can nurse up to 45 minutes at a time.” [1] It’s important to observe the puppies nursing frequently, especially in the first 24 hours, to ensure they are getting adequate milk.

The VCA Hospitals advise that when feeding orphaned puppies with a bottle, “Never prepare more milk replacer than can be used within 24 hours.” [2] This highlights the importance of fresh milk from the mother’s nipples for proper nutrition.

In summary, nipples allow newborn puppies to receive the nourishing colostrum and milk they need to survive and thrive in their initial days and weeks.

Nipple Health

Just like human nipples, dog nipples can develop problems that require monitoring and care. Some common nipple issues in male dogs include:

  • Inflammation or redness – This can occur from infection, trauma, or skin irritation. Keeping the area clean and dry can help prevent inflammation.
  • Inverted nipples – Some dogs have nipples that invert or sink into the skin instead of protrude outward. This is usually normal but can make the nipples prone to irritation.
  • Nipple discharge – Fluid or pus leaking from the nipples may indicate an infection or other medical issue requiring veterinary attention.
  • Tumors – While rare, dogs can develop benign or cancerous growths on the nipples. Any lumps or changes should be checked by a vet.

Regularly inspecting your dog’s nipples and keeping the area clean is important to nip any problems in the bud. See your veterinarian if you notice any concerning nipple issues such as bleeding, odor, or skin changes. With prompt care, most nipple problems can be managed or resolved.

For more information, see this veterinary resource: How to Properly Clean Your Dog’s Nipples

Spaying/Neutering Effects

Spaying or neutering a dog can cause changes to the dog’s nipples and mammary glands. When a female dog is spayed, which involves surgical removal of the ovaries and uterus, her body stops producing the hormones estrogen and progesterone. These hormones are responsible for heat cycles and pregnancy in intact female dogs. Without these hormones, the mammary glands will start to shrink, which causes the dog’s nipples to shrink as well (source: https://caninehq.com/effects-of-spaying-on-dogs-nipples/).

The nipples usually begin to shrink within 1-2 months after spaying surgery. However, the amount of shrinkage depends on factors like the dog’s age at time of spay and how many heat cycles she experienced before being spayed. The nipples of dogs spayed at a younger age will generally shrink more than dogs spayed when older. Dogs that were spayed before ever going into heat may have nipples that shrink back down to the size they were before puberty (source: https://petdogowner.com/do-dogs-nipples-shrink-after-spaying/).

In male dogs, neutering or castration involves surgical removal of the testicles, which are the main source of the hormone testosterone. Loss of testosterone causes male dogs’ mammary glands and nipples to shrink over time, similarly to spayed females. However, the effects are usually less pronounced in males (source: https://www.quora.com/My-dog-is-spayed-and-out-of-no-where-her-nipples-are-getting-bigger-and-so-is-her-private-part-We-did-take-her-to-the-vet-but-they-said-it-s-just-probably-because-she-licks-that-part-a-lot-But-it-s-been-weeks-and).

Fun Nipple Facts

Did you know that the number of nipples a dog has actually varies? According to https://www.dogster.com/dog-health-care/dog-nipples, the number can range from 6 to 10 on average.

Also, puppies don’t actually nurse from every nipple! The AKC says they tend to find one or two favorite nipples to feed from. So those extra nipples come in handy if their favorites are already being nursed on by another puppy in the litter.

Additionally, some dogs can even develop an extra nipple later in life. Though rare, this is called a polythelia and can occur from hormone imbalances. So if you notice an odd new bump, get your vet to check it out.

Finally, hair does not normally grow around dog nipples. So if you see some furry nipples, it could be a sign of a hormonal disorder according to https://www.akc.org/expert-advice/health/male-dogs-nipples/. As always, consult your vet if something seems abnormal.


In summary, male dogs have anywhere from 8 to 10 nipples due to biology and the evolution of the mammal. While most male dog nipples serve no real purpose, they are still a normal part of canine anatomy. Understanding the number and appearance of a dog’s nipples can help owners monitor their health and identify any issues early on. The takeaway is that those seemingly useless nipples on your male pup are not abnormal – they are simply leftovers from ancient canine ancestors who needed them for feeding large litters. So the next time you notice your male dog’s surplus of nipples, no need to be alarmed – it’s just a quirk of nature!

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