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Which Animal Has the Largest Breasts?

Animals and Breast Size

Before you get to thinking any deeper – we're coming out clean. By breasts, we're actually referring to the mammary glands. Female humans are the only species on earth to have pronounced breasts even when they aren't breastfeeding. Even when other mammals are breastfeeding, they simply don't have breasts like humans do. It's a contest without competition really.

To learn which animal has the largest breasts, you need to know that only mammals have "breasts" for child-rearing, the same way that only mammals have hair. Reptiles, birds and other classes and subclasses of animals do not have nipples and breasts, as the ability to produce milk is something unique to mammals alone. This is, of course, the reason they're called "mammary" glands in the first place.

Most female mammals give live birth to fully developed young. This means that their offspring has had time to develop inside the womb. This mode of reproduction, known as viviparous, produces offspring with more advanced developments, rather than those produced through means of egg-laying and non-placental, internal fertilization.

Anyway, this viviparity is an essential idea to wrap your head around because it's the first step for some mammals to get prominent, child-rearing breasts. In some non-human mammals, having a prominent breast is a sign of fertility.

As soon as (or even before) a mother gives birth to a live young, the mother starts producing milk that causes the breasts to be prominent in the case of other animals, or more prominent in the case of humans. As their young weans from the milk, both humans and animals at some point stop lactating. A female's breast starts to return to its natural size, and an animal's "breast" returns to a normal, flat surface. On the other hand, many mammals, such as gorillas and apes, do not have prominent breasts even when their mammary glands are full of milk.

Now, for the sake of scientific curiosity, let's start learning about mammals and their interesting breasts and nipples.

Ruminants and Their Udders and Teats

A cow's breasts and nipples are known as udders and teats. Unlike the human mammary glands, a cow's mammary glands are made up of ducts that flow into a single reservoir that is usually located between the hind legs of the animal. In a human, that location would be around the stomach area. While a human breast discharges milk from numerous ducts out of the nipples, a cow's udder can only discharge its milk through a single duct out of each four teats. A large cow udder does not always mean more milk. However, how large a cow's teat meatus (or the teat orifice) is an important factor in how fast you can milk a cow.

It's also worth noting that udder health is a factor considered by many cow ranchers about who stays and who goes. The health of a cow's udders contributes to the health of a cow's calves. So much so that there is actually a scoring system used for evaluating udder health. This helps ranchers determine which calves have the best chance to grow into healthy cows themselves.

When humans have more than two, known as supernumerary ones, removal is only done for cosmetic reasons. This condition is more common in men than in women. And, these ones may lactate in both genders. In any case, extra ones in humans don't serve as symptoms of other underlying conditions. Neither can they cause any health problems on their own.

This isn't the case with goats, though. An extra one on milk goats is considered a deformity. They may be caused when a goat's kid is exposed to harmful toxins while still in the womb.

Underwater Mammals and the World's Heaviest Mammaries

If you're guessing that an underwater mammal is the answer to the question of "Which animal has the largest breast?" – you're right, more or less. Most mammals don't have human-like breasts, but they sure pack some interesting mammary glands. Take the blue whale, for example.

A blue whale's mammary glands are the largest in the world. A blue whale's breast is only as big as a small person at five feet long, but it's as heavy as a newborn elephant at 250 pounds . . . and that's only for a single mammary gland!

Underwater mammary glands don't work like a human's. For one, they don't have anything that resembles a human breast. Second, all blue whales have inverted ones that only come out with stimulation from the baby whale. The milk is ejected from them. They're not sucked, and babies just kind of catch the milk as it's ejected from their mother.

Blue whale calves come out enormous, but they still need lots of sustenance. A blue whale's milk fat and protein content is 1000% higher than a human's! It has a protein content of about 12% and a fat content of about 38%. This high fat and protein content is quite logical.

Baby whales should pack on about 37,500 pounds of weight before they wean from their mother's milk, and they need all the nutrients they can get. Because their milk is so fatty, it doesn't dissipate in the water right away, giving them more time to consume the milk.

The hooded seal also shares this ability to make fatty breast milk. A hooded seal's milk can have as much as 61% of fat. However, baby seals enjoy this fatty, nutritious milk for just four days. They need to drink as much as they can because they'd be on their own while their mothers go back into the cold waters to find food.

Blue whale

Blue whale

Monotremes and Their Non-existent Feeding Organs, Like Mammals

There are only five species of monotremes in the world, and these five species are the only species of mammals that are not viviparous. The entire living subclass is made up of four echidna species and the platypus. Like reptiles, a monotreme lays eggs. Like marsupials, monotremes store these eggs in an external pouch where the eggs develop. Finally, like every mammal, monotremes rear their young with milk from their mammary glands.

However, monotremes do not have both, so how in the world do they feed their young? Why, through their mammary hair, of course! A monotreme's mammary glands produce milk that is released through the pores. It eventually makes its way to patches of fur that the young monotremes suck on.

Animal class/speciesNumber of teats



Sheep, dear and goat


Blue whale




Virginian opossum



8 to 10


6 to 32

Marsupials and Their Non-conventional Organs

Mammals almost always have pairs of teats. Those with extra ones and non-symmetrical teats are a rare sight. Almost. The Virginia opossum is a weird exception. Virginian opossums have 13. Twelve of them are arranged in a neat circle inside the opossum's pouch, while the 13th one sits pretty in the middle of the circle.

Like other marsupials, the Virginia opossum gives birth to live fetuses. These fetuses are underdeveloped – blind, hairless and deaf to start with, though they already have their claws. They use these claws to crawl around their mother's pouch, going around and looking for a nipple. Once they latch onto the nipple, they'll stay there and feed for a whole two months. To help the babies latch on better, the nipples expand and can even be stretched up to 35 times the normal length during this period.

Not all 13 teats could work though, and the number of working teats varies per individual. The number of working teats determines how many babies it can rear at every breeding season. If an opossum couldn't find a teat or has run out of teats to latch onto, they could die within minutes. If all 13 teats are working, a Virginia opossum can take care of 13 babies at a time.

So Which Animal Has the Largest Breast?

If you're in a joking mood, you can always answer the question with "zebra", because it wears a z-bra! Get it?

But, if you're looking for a serious answer, the blue whale takes the cake. The blue whale has the biggest, heaviest mammary glands, but they are by far the most interesting breasts in the animal kingdom. Aside from the animals in this short read, there are still a lot of other interesting animals with their equally interesting breasts!

Now that you know which animal has the largest breasts, why not try and discover how many of your friends know it too? Share this article with your friends and find out!