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Which mammal produces the most milk?

Which mammal produces the most milk?


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I'm searching for the mammal species that can produce the most milk during lactation. I Googled it, but it says dairy cattle which biologically speaking is not right answer, because a baby whale can drink up to 150 gallons (> 550 litres) of milk per day (according to whalefacts.org). So which mammal can produce the most milk?


Colostrum

Colostrum (known colloquially as beestings, [1] bisnings [2] or first milk) is the first form of milk produced by the mammary glands of mammals (including humans) immediately following delivery of the newborn. [3] Most species will begin to generate colostrum just prior to giving birth. Colostrum has an especially high amount of bioactive compounds compared to mature milk to give the newborn the best possible start to life. Specifically, colostrum contains antibodies to protect the newborn against disease and infection, and immune and growth factors and other bioactives that help to activate a newborn’s immune system, jumpstart gut function, and seed a healthy gut microbiome in the first few days of life. The bioactives found in colostrum are essential for a newborn’s health, growth and vitality.

At birth, the surroundings of the newborn mammal change from the relatively sterile environment in the mother’s uterus, with a constant nutrient supply via the placenta, to the microbe rich environment outside with irregular oral intake of complex milk nutrients through the gastrointestinal tract. [4] This transition puts high demands on the gastrointestinal tract of the neonate, as the gut plays an important part in both the digestive system and the immune system. [5] Colostrum has evolved to care for highly sensitive mammalian neonates and contributes significantly to initial immunological defense as well as to the growth, development, and maturation of the neonate’s gastrointestinal tract by providing key nutrients and bioactive factors. [6] [7]

Colostrum also has a mild laxative effect, encouraging the passing of the baby's first stool, which is called meconium. This clears excess bilirubin, a waste-product of dead red blood cells, which is produced in large quantities at birth due to blood volume reduction from the infant's body and helps prevent jaundice.


10 Highly-Productive Animals to Raise for Dairy (Other Than Milk Cow)

Jennifer is a full-time homesteader who started her journey in the foothills of North Carolina in 2010. Currently, she spends her days gardening, caring for her orchard and vineyard, raising chickens, ducks, goats, and bees. Jennifer is an avid canner who provides almost all food for her family needs. She enjoys working on DIY remodeling projects to bring beauty to her homestead in her spare times.

When I first began homesteading I had all of these thoughts of milking daily and making my own cheese. I do these things, just not in the way I had imagined.

You see, I thought if I ever lived this life I would need to have a cow. A big, fat traditional cow.

Yet, when we ended up farming on a smaller amount of acreage, I knew that a traditional dairy cow was out. The reason is that they require so much room to graze.

Now, don’t get me wrong. I’ve seriously considered buying hay and throwing a cow out in my front yard. Thankfully, my husband has talked me out of that idea a few times.

However, I want to share with you a few alternative dairy options. Not all of them will be suitable for a small scale homesteader, but they are interesting none the less.

Also, some of these options for milk animals are common in different parts of the world.

So keep an open mind as we explore the list of milk animals.

1. Small Breed Dairy Cow

These are not cheap options, but I have considered them in years past. They actually make a breed of dairy cow that is known as a micro-miniature. This means that they are 36-inches in height and under, but don’t let their small size fool you.

Though they are smaller breeds, they still give around a gallon each milking session. They do require room to forage and graze but are obviously much more manageable than a full-sized cow.

However, this still means that each cow would need a half-acre to an acre to be fully sustained on your land.

If you have room on your property and in your budget to purchase one of these small cows, it might be a wise investment.

2. Camels

When I first saw this I thought, “What?” However, think about it. In other parts of the world where they don’t have the grazing options, they have to find milk from an animal that can sustain itself in really hot weather.

Why not the camel? It is a very resilient animal and depending upon the breed, you can get anywhere from 5-40 liters of milk per day.

However, you might be thinking, “Is this realistic for me?”

Well, not if you live on a small scale farm like myself. Camels actually need 2-acres of land per camel.

However, you can make quite a bit of money off of owning a camel, and you don’t need to live in a really warm climate.

When I was growing up, my grandparents lived in Kentucky. Sure enough, there was a farm up the road from them that owned camels.

So if you’d like a different dairy source and have the room, you might consider owning a camel.

3. Horses

Maybe you want dairy from your homestead, but you don’t have the funds to invest in a dairy cow. However, you already raise horses.

Well, if you can get past the stigma that we ‘only drink cow’s milk’ then drinking horse milk might be an option for you. It is something that is practiced in Central Asia. People don’t always have the means to support a variety of livestock so they make do with what they have.

Again, this may not be a suitable option for a milk animal for everyone, but if you are feeling adventurous and want to make-do until you can afford to buy a dairy cow, then you might like the idea of utilizing your horses for more than just riding.

4. Yaks

In parts of the world where people live in very high mountainous areas, they raise yaks for dairy. Their milk is very rich and considered quite a delicacy in most parts of the world.

According to my research, most areas do not require you to have a special permit to raise yaks. They are actually considered domesticated animals. They are also great for bringing a profit to your homestead.

Just in case you were curious, people love their meat because of how lean it is. It is a red meat source as well. Yaks also bring a lot of money for their skin. People make nice robes out of them.

However, one of the greatest things about raising a yak is that they are quieter than a dairy cow. Instead of mooing, they simply grunt.

If you have the space to raise a herd of yaks, then you might want to consider it. Some people actually claim that they are the substitute Bovine.

5. Buffaloes

Growing up, there was this great little restaurant near our home that served buffalo burgers. At first, the idea of eating a buffalo burger kind of freaked me out.

However, after I tried it, I still think it was the tastiest burger I had ever eaten.

Still, did you know that buffalos are also raised as a dairy source? I know, getting past some of these stigmas is tough. Still, what if you’d like to raise a meat and dairy product in one that is different from a cow?

Why shouldn’t you consider the buffalo? Not to mention, their milk makes exquisite cheeses because of the high-fat content.

Also, water buffalo are great beyond just meat and dairy. They are slow-moving animals, but they are also very sturdy which makes them great for riding and using around the homestead.

If you have the land and just don’t want to invest in cattle, then you might want to give buffalo a thought.

6. Donkeys

If you ask me, donkeys are truly amazing creatures. They are wonderful livestock protectors and very functional animals around a homestead.

However, have you ever considered keeping them for dairy too? It might not be the most common type of milk, but there are countries around the world that only have this type of milk so they use it.

Well, if you’d like dairy and only have a donkey then you might want to consider giving it a try. The truly interesting thing about donkey’s milk is that it is easier to digest than other types of milk.

Also, it is very close to human milk so many people with milk allergies can digest this type of milk. It is also great for cooking purposes, too.

If you have a donkey, before you go into debt for a milk cow, consider giving their milk a try.

7. Sheep

I’m seriously considering adding sheep to our homestead. Their meat is wonderful, their personalities are great, and you can also use them for milk.

Now, sheep are quite common for dairy usage throughout the world. Actually, they were used for milk long before cows even were.

And their milk is a lot more nutritious than cow’s milk too. It has more vitamins, calcium, phosphorus, potassium, and magnesium than cow’s milk.

So if you like the idea of raising a smaller, multipurpose animal that can also provide healthier milk then you might want to consider sheep.

Plus, if you are shorter on land then sheep might be a good option for you. The reason is that 6 sheep can easily fit on an acre of land. This means you could easily fit a small number of sheep on a small to medium-sized homestead.

8. Nubian Goats

A Nubian goat is another addition that is coming soon to our homestead. The reason is that they are actual dairy goats. Their milk is deemed to be the closest to cow’s milk.

However, goat’s milk is easier to digest just like donkey milk. So if you have an allergy to regular cow’s milk, you might be able to handle goat’s milk.

A Nubian goat will give approximately 1-gallon of milk a day and has around 4-5% in butterfat. Plus, Nubians are always noted for the sweet taste that their milk contains.

This means, if you don’t have room for a cow then you might very well have room for a Nubian goat on your homestead. Then you can have all of the milk your family could possibly need.

9. Boer Goats

I have a Boer goat. She is wonderful and very sweet.

However, when I first bought goats I knew I didn’t want to invest a lot of money in them because I was new to raising them.

I got a great deal on her, and I thought I’d try to milk her.

Now, people thought I was nuts because everyone told me I couldn’t milk a non-dairy breed of a goat. Even so, stubborn me showed them otherwise.

The first time she kidded she gave us twins and made an ample amount of milk to support them and us. The average for a Boer goat is about 4.4 pounds of milk a day.

As far as ease of milking, she had a huge bag and her udders were a good size to make milking easy.

If you can’t afford a Nubian but find a cheaper goat, then go for it. It is still a functional way to get milk, at least in my own experience.

10. Pygmy Goats

I had a lady laugh at me when I told her I have a Pygmy goat for milk. She told me there was no way we could milk them. That their udders were too small.

Well, let me tell you, you can milk a Pygmy goat. Our Pygmy was our very first goat. She is my absolute favorite, and I hope to have more of them in the future.

Their demeanors are so great, and they are also so easy to handle because of their small stature.

However, don’t let their small stature fool you. Our Pygmy delivered 3 babies her first time kidding.

Plus, she gave us an ample amount of milk and was easier to milk because of her demeanor.

On average a Pygmy goat can produce around a quart of milk per day, but what I love most about goats is that their milk is easier to digest and you don’t have to worry about over milking.

They actually have a way of withholding the milk their babies need. That was a huge relief. You’ll just need to be sure that you don’t milk a goat within 2 months of her kidding (if you are freshening her milk supply) in order for her to store up needed nutrients for the kids.

Well, there you have it, folks. If you have been stuck in a dairy rut and weren’t quite sure where to turn for some unique or smaller options for dairy, well, now you know that you have choices.

Remember, not all of these are common in some corners of the world, but they are practiced in others.

Just do a little research to see which option for a milk animal you think might work best for you. Also, be aware of the animal’s needs before jumping into it.


Seven of the Most Extreme Milks in the Animal Kingdom

A mother’s breastmilk contains a concoction of nutrients—mainly fats, proteins and carbohydrates—essential for a baby’s development. It also contains a cocktail of protective factors that help vulnerable babies fight off harmful microbes.

Related Content

Breastmilk is not a uniquely human feature. All mammals produce milk, and each mammalian species produces its own special blend best suited for its babies. Figuring out how and why milk differs across species can help scientists better understand how human breastmilk influences infant development and growth, which can be especially useful for designing supplemental formulas for babies.

Here are some examples of the most extreme milks found in nature:

Hooded seals (Cystophora cristata)

(JORGE ZAPATA/epa/Corbis)

Hooded seal mothers produce the fattiest known milk. Human breastmilk has about three to five percent fat in it. But with more than 60 percent fat, hooded seal milk would rival some of the richest Häagen-Dazs ice creams out there. Such a high-fat diet is crucial for the seal pups, because these animals are born into the freezing waters of the North Atlantic and Arctic oceans. Seal mothers give birth to pups on floating ice, an environment that is both unstable and unreliable. So the mother seal feeds her pups for only four days, packing a lot of energy-dense fat into her milk.

During this super-short nursing period, the pups can consume about 16.6 pounds of milk every day. By the time they are weaned, they are almost double in weight, researchers have found. The high-fat diet helps the pups put on a thick layer of blubber that serves to insulate their bodies against the harsh, cold environment, says Amy Skibiel, a lactation expert at the University of Florida.

Black Rhinoceros (Diceros bicornis)

(JMWScout/iStock)

By contrast, the black rhinoceros has the skimmest milk on the fat spectrum. A rhino mom produces milk that is watery and has only about 0.2 percent fat. This dilute milk may have something to do with the animals' slow reproductive cycle. Black rhinoceroses become capable of reproducing only once they reach four to five years old. They have long pregnancies that last for over a year, and they give birth to one calf at a time. Then they spend a considerable amount of time—almost two years—nursing their young.

In a 2013 study, Skibiel’s team found that species that lactate for longer durations tend to have lower fat and proteins in their milk. “And that makes sense, because if a female were lactating for a few years and really investing in putting a lot of nutrients into her milk, that’s not really sustainable over a long period of time,” Skibiel says. “That’s probably the reason why we see such low fat in the black rhinoceros milk.”

Tammar Wallabies (Macropus eugenii)

(Wayne Lynch/All Canada Photos/Corbis)

Tammar wallabies, found in southern and western Australia, produce sugar-rich milk for their joeys. Their milk contains about 14 percent sugar, double the amount present in human milk and one of the highest levels among mammals. The types of sugars in their milk are different, too. The predominant sugar in human milk is lactose—a sugar that breaks down into glucose and galactose. However, milk of the tammar wallabies has very little lactose in it, and instead consists of high levels of other complex sugars called oligosaccharides. The reasons for this difference are still under investigation, but one idea is that the milk oligosaccharides may serve an anti-microbial purpose in a developing joey’s gut.

Many marsupials, or pouched mammals, like tammar wallabies also have a unique way of controlling what goes into their milk depending on the ages of their young. For example, a tammar wallaby mother could be suckling an older joey from one nipple and an infant joey still in her pouch from another nipple, and she can produce two different milks for each of them. The younger joey may enjoy milk rich in sugars, while the older one gets milk higher in proteins and fat. “It’s quite incredible that they are capable of producing two entirely different milks that are suited for the stage that that young is in,” Skibiel says. 

Eastern Cottontail Rabbits (Sylvilagus floridanus)

(jmontgomerybrown/iStock)

Milk from the eastern cottontail rabbit has around 15 percent protein in it—the most protein-rich milk researchers have found so far—and is also rich in fats. According to researchers, milk with high levels of both fats and proteins is seen among species that leave their young unattended for extended periods of time, while the mothers go off to forage. Cottontail rabbit mothers, for instance, return to their ground nests to nurse their young only once or twice a day.

“So during those times when they are nursing, the rabbit pups are probably consuming a greater amount of milk,” Skibiel says. “And that milk is going to be higher in density, or richer in nutrients, basically to compensate for the time that they are away from their mothers and are not able to suckle.” Following such a rich diet, the young rabbits mature quickly and are able to fend for themselves after only a few weeks of suckling their mother’s milk.

Pigs (Sus domesticus)

(balwan/iStock)

Pig milk is slightly fattier than cow milk but has similar amounts of proteins and sugars. Why then do we drink cow’s milk but not pig’s? The answer comes down to a physical limitation: sows are very difficult to milk. The female pigs have around 14 small teats, compared with the four large nipples on a cow's udder. Sows also eject milk to their suckling piglets in bursts that last only up to a minute, so you would have to wait for a really long time to collect even half a liter of milk. By contrast, cows store their milk in their udders and can eject milk continuously for several minutes at a time.

However, recently a farm in the Netherlands produced cheese from pig’s milk. The rare product, which reportedly tastes saltier and creamier than traditional cow’s milk cheese, sells at a whopping $1,200 per pound.

Pigeons (Columba livia)

(hila335/iStock)

Mammals may have a monopoly on milk, but some birds, like pigeons, produce a milk-like substance for their babies, too. And unlike mammals, both male and female pigeons produce this milky substance to feed their young squabs. Pigeon parents produce what is known as crop milk, which is secreted into a small sac at the base of their throats that normally stores and moistens food. Once a squab is born, the pigeons regurgitate crop milk into the baby bird's mouth.

Pigeon milk mostly has high levels of proteins and fats, as well as some minerals and other nutrients. Flamingoes and emperor penguins are also known to produce crop milk for their young.

Humans (Homo sapiens)

(jaqy/iStock)

In her 2013 study, Skibiel found that, in general, closely related species have similar patterns of milk composition. For instance, the low-fat, low-protein and high-sugar blend of human milk does follow the typical pattern of most other primate milk. Humans also nurse their babies for long periods of time in general—sometimes up to a few years. And like black rhinoceroses’ milk, the longer nursing period means that humans tend to invest fewer energy-rich nutrients into their milk.

We still have a long way to go before we completely demystify human milk. For example, human milk, like that of tammar wallabies, has an array of complex sugars called oligosaccharides. Researchers are only beginning to understand the role these sugars play in fortifying human infants. Still, there’s a lot more research going into human milk than into milks of other species, Skibiel says. Scientists know the milk compositions of only 5 percent of the mammals living today.

“So some of the things that we know about human milk may not necessarily be unique. We just don’t know if they exist in the milks of other species yet. And we don’t have the data to make a comparative analysis.” 


Mammals 'Got Milk' for Past 160 Million Years

Moms today are strongly encouraged to nurse their babies. Mother's milk is more nourishing than formula and provides infants with some immune protection.

This makes intuitive sense. Mammals and milk go together — it is produced by all species in this group and apparently has been for at least 160 million years.

A new study looks at the genes that produce milk among seven species of mammals, including us, and finds that all of them share a lot of the same milk-making genes but not all species deliver the same milk. In fact, the milk might be tailored to the specific immune system needs of the animals.

Researchers with the Bovine Lactation Genome Consortium compared 197 milk and mammary genes from cattle, (Bos taurus aka European cattle), and more than 6,000 mammary-related genes, with other genes in the bovine genome.

They also compared these milk and mammary genes with similar ones from a platypus (one of only two species of mammals that lay eggs rather than giving birth to live young), opossum (a marsupial, which carries young in a pouch after birth), human, dog, mouse and rat.

By comparing the genes of these species of mammals, the team discovered that, compared to other cattle genes, the individual milk and milk-production genes are more likely to be found in all mammals, despite the wide diversity of lactation strategies. Milk-production genes also are less likely to have changed as news species evolved.

"The most recent common ancestor of these seven mammals would have lived around 160 million years ago," said Danielle Lemay, the lead author on the milk genome study and a bioinformatician and nutrition scientist in the University of California, Davis, Department of Food Science and Technology. "Therefore, it is expected that these genes existed in the common ancestor 160 million years ago."

Mammals' origins go back to mammal-like reptiles called synapsids. The first synapsids occur in the fossil record about 310 million years ago.

The milk genome

The milk-genome researchers focused on cattle genes involved with milk and the lactation process because of the role that milk plays in the lives of cattle, humans and all other mammals.

"Because milk is produced for offspring at great physiological expense to the mother, we can theorize that there are few superfluous components in milk," said UC Davis professor and food scientist Bruce German, a member of the consortium. "Generation after generation, those animals that are able to produce more nourishing milk perpetuate their genes through the survival and reproductive success of their offspring."

The researchers narrowed the search for genes that affect milk traits by overlaying the genetic data on existing information regarding 238 DNA segments that are known to be associated with particular traits.

"Overall, the findings of our study support the hypothesis that the biological roots of milk production in mammals are quite ancient and that the evolution of milk has been constrained in order to maximize the survival of both mother and offspring," said Juan Medrano, a professor of animal genetics at the University of California, Davis, and also a consortium member.

Secreting milk v. immune boosting

The researchers also found that the milk proteins that remained the same across species were those proteins related to secreting milk in mammals. Conversely, those milk proteins that had diverged the most from species to species were those associated with the nutritional and immunological components of milk.

This suggests that the immunological component of milk is tailored to the particular needs of each species and highlights the need for future nutrition research to examine how foods might be tailored to meet individual immunological needs, the researchers noted.

The results were detailed in the April 24 issue of the online journal Genome Biology, timed to come out the same day that the entire cattle genome was published in the journal Science. That project took six years and involved more than 300 scientists from 25 countries. It was coordinated by the Baylor College of Medicine Human Genome Sequencing Center.


Contents

Extant species

Image Common name Scientific name Distribution
Bactrian camel Camelus bactrianus domesticated Central Asia, including the historical region of Bactria.
Dromedary / Arabian camel Camelus dromedarius domesticated the Middle East, Sahara Desert, and Afghanistan introduced to Australia
Wild Bactrian camel Camelus ferus Remote areas of northwest China and Mongolia

The average life expectancy of a camel is 40 to 50 years. [12] A full-grown adult dromedary camel stands 1.85 m (6 ft 1 in) at the shoulder and 2.15 m (7 ft 1 in) at the hump. [13] Bactrian camels can be a foot taller. Camels can run at up to 65 km/h (40 mph) in short bursts and sustain speeds of up to 40 km/h (25 mph). [14] Bactrian camels weigh 300 to 1,000 kg (660 to 2,200 lb) and dromedaries 300 to 600 kg (660 to 1,320 lb). The widening toes on a camel's hoof provide supplemental grip for varying soil sediments. [15]

The male dromedary camel has an organ called a dulla in its throat, a large, inflatable sac he extrudes from his mouth when in rut to assert dominance and attract females. It resembles a long, swollen, pink tongue hanging out of the side of its mouth. [16] Camels mate by having both male and female sitting on the ground, with the male mounting from behind. [17] The male usually ejaculates three or four times within a single mating session. [18] Camelids are the only ungulates to mate in a sitting position. [19]

Ecological and behavioral adaptations

Camels do not directly store water in their humps they are reservoirs of fatty tissue. When this tissue is metabolized, it yields more than one gram of water for every gram of fat processed. This fat metabolization, while releasing energy, causes water to evaporate from the lungs during respiration (as oxygen is required for the metabolic process): overall, there is a net decrease in water. [20] [21]

Camels have a series of physiological adaptations that allow them to withstand long periods of time without any external source of water. [23] The dromedary camel can drink as seldom as once every 10 days even under very hot conditions, and can lose up to 30% of its body mass due to dehydration. [24] Unlike other mammals, camels' red blood cells are oval rather than circular in shape. This facilitates the flow of red blood cells during dehydration [25] and makes them better at withstanding high osmotic variation without rupturing when drinking large amounts of water: a 600 kg (1,300 lb) camel can drink 200 L (53 US gal) of water in three minutes. [26] [27]

Camels are able to withstand changes in body temperature and water consumption that would kill most other mammals. Their temperature ranges from 34 °C (93 °F) at dawn and steadily increases to 40 °C (104 °F) by sunset, before they cool off at night again. [23] In general, to compare between camels and the other livestock, camels lose only 1.3 liters of fluid intake every day while the other livestock lose 20 to 40 liters per day (Breulmann, et al., 2007). [28] Maintaining the brain temperature within certain limits is critical for animals to assist this, camels have a rete mirabile, a complex of arteries and veins lying very close to each other which utilizes countercurrent blood flow to cool blood flowing to the brain. [29] Camels rarely sweat, even when ambient temperatures reach 49 °C (120 °F). [30] Any sweat that does occur evaporates at the skin level rather than at the surface of their coat the heat of vaporization therefore comes from body heat rather than ambient heat. Camels can withstand losing 25% of their body weight to sweating, whereas most other mammals can withstand only about 12–14% dehydration before cardiac failure results from circulatory disturbance. [27]

When the camel exhales, water vapor becomes trapped in their nostrils and is reabsorbed into the body as a means to conserve water. [31] Camels eating green herbage can ingest sufficient moisture in milder conditions to maintain their bodies' hydrated state without the need for drinking. [32]

The camel's thick coat insulates it from the intense heat radiated from desert sand a shorn camel must sweat 50% more to avoid overheating. [33] During the summer the coat becomes lighter in color, reflecting light as well as helping avoid sunburn. [27] The camel's long legs help by keeping its body farther from the ground, which can heat up to 70 °C (158 °F). [34] [35] Dromedaries have a pad of thick tissue over the sternum called the pedestal. When the animal lies down in a sternal recumbent position, the pedestal raises the body from the hot surface and allows cooling air to pass under the body. [29]

Camels' mouths have a thick leathery lining, allowing them to chew thorny desert plants. Long eyelashes and ear hairs, together with nostrils that can close, form a barrier against sand. If sand gets lodged in their eyes, they can dislodge it using their transparent third eyelid. The camels' gait and widened feet help them move without sinking into the sand. [34] [36] [37]

The kidneys and intestines of a camel are very efficient at reabsorbing water. Camels' kidneys have a 1:4 cortex to medulla ratio. [38] Thus, the medullary part of a camel's kidney occupies twice as much area as a cow's kidney. Secondly, renal corpuscles have a smaller diameter, which reduces surface area for filtration. These two major anatomical characteristics enable camels to conserve water and limit the volume of urine in extreme desert conditions. [39] Camel urine comes out as a thick syrup, and camel faeces are so dry that they do not require drying when the Bedouins use them to fuel fires. [40] [41] [42] [43]

The camel immune system differs from those of other mammals. Normally, the Y-shaped antibody molecules consist of two heavy (or long) chains along the length of the Y, and two light (or short) chains at each tip of the Y. Camels, in addition to these, also have antibodies made of only two heavy chains, a trait that makes them smaller and more durable. These "heavy-chain-only" antibodies, discovered in 1993, are thought to have developed 50 million years ago, after camelids split from ruminants and pigs. [44] Camels suffer from surra caused by Trypanosoma evansi wherever camels are domesticated in the world, [45] and resultantly camels have evolved trypanolytic antibodies as with many mammals. In the future, nanobody/single-domain antibody therapy will surpass natural camel antibodies by reaching locations currently unreachable due to natural antibodies' larger size. Such therapies may also be suitable for other mammals. [46]

Genetics

The karyotypes of different camelid species have been studied earlier by many groups, [47] [48] [49] [50] [51] [52] but no agreement on chromosome nomenclature of camelids has been reached. A 2007 study flow sorted camel chromosomes, building on the fact that camels have 37 pairs of chromosomes (2n=74), and found that the karyotype consisted of one metacentric, three submetacentric, and 32 acrocentric autosomes. The Y is a small metacentric chromosome, while the X is a large metacentric chromosome. [53]

The hybrid camel, a hybrid between Bactrian and dromedary camels, has one hump, though it has an indentation 4–12 cm (1.6–4.7 in) deep that divides the front from the back. The hybrid is 2.15 m (7 ft 1 in) at the shoulder and 2.32 m (7 ft 7 in) tall at the hump. It weighs an average of 650 kg (1,430 lb) and can carry around 400 to 450 kg (880 to 990 lb), which is more than either the dromedary or Bactrian can. [54]

According to molecular data, the wild Bactrian camel (C. ferus) separated from the domestic Bactrian camel (C. bactrianus) about 1 million years ago. [55] [56] New World and Old World camelids diverged about 11 million years ago. [57] In spite of this, these species can hybridize and produce viable offspring. [58] The cama is a camel-llama hybrid bred by scientists to see how closely related the parent species are. [59] Scientists collected semen from a camel via an artificial vagina and inseminated a llama after stimulating ovulation with gonadotrophin injections. [60] The cama is halfway in size between a camel and a llama and lacks a hump. It has ears intermediate between those of camels and llamas, longer legs than the llama, and partially cloven hooves. [61] [62] Like the mule, camas are sterile, despite both parents having the same number of chromosomes. [60]

Evolution

The earliest known camel, called Protylopus, lived in North America 40 to 50 million years ago (during the Eocene). [18] It was about the size of a rabbit and lived in the open woodlands of what is now South Dakota. [63] [64] By 35 million years ago, the Poebrotherium was the size of a goat and had many more traits similar to camels and llamas. [65] [66] The hoofed Stenomylus, which walked on the tips of its toes, also existed around this time, and the long-necked Aepycamelus evolved in the Miocene. [67]

The ancestor of modern camels, Paracamelus, migrated into Eurasia from North America via Beringia during the late Miocene, between 7.5 and 6.5 million years ago. [68] [69] [70] Around 3–5 million years ago, the North American Camelidae spread to South America as part of the Great American Interchange via the newly formed Isthmus of Panama, where they gave rise to guanacos and related animals, and to Asia via the Bering land bridge. [18] [63] [64] Paracamelus continued to exist in the Canadian high Arctic into the Pleistocene, around 1 million years ago. [71] [72] This creature is estimated to have stood around nine feet (2.7 metres) tall. [73] The Bactrian camel diverged from the dromedary about 1 million years ago, according to the fossil record. [74]

The last camel native to North America was Camelops hesternus, which vanished along with horses, short-faced bears, mammoths and mastodons, ground sloths, sabertooth cats, and many other megafauna, coinciding with the migration of humans from Asia. [75] [76]

Like horses, camels originated in North America and eventually spread across Beringia to Asia. They survived in the Old World, and eventually humans domesticated them and spread them globally. Along with many other megafauna in North America, the original wild camels were wiped out during the spread of the first indigenous peoples of the Americas from Asia into North America, 10 to 12,000 years ago although fossils have never been associated with definitive evidence of hunting. [75] [76]

Most camels surviving today are domesticated. [43] [77] Although feral populations exist in Australia, India and Kazakhstan, wild camels survive only in the wild Bactrian camel population of the Gobi Desert. [12]

History

When humans first domesticated camels is disputed. The first domesticated dromedaries may have been in southern Arabia around 3000 BCE or as late as 1000 BCE, and Bactrian camels in central Asia around 2500 BCE, [18] [78] [79] [80] [81] as at Shahr-e Sukhteh (also known as the Burnt City), Iran. [82]

Martin Heide's 2010 work on the domestication of the camel tentatively concludes that humans had domesticated the Bactrian camel by at least the middle of the third millennium somewhere east of the Zagros Mountains, with the practice then moving into Mesopotamia. Heide suggests that mentions of camels "in the patriarchal narratives may refer, at least in some places, to the Bactrian camel", while noting that the camel is not mentioned in relationship to Canaan. [83]

Recent excavations in the Timna Valley by Lidar Sapir-Hen and Erez Ben-Yosef discovered what may be the earliest domestic camel bones yet found in Israel or even outside the Arabian Peninsula, dating to around 930 BC. This garnered considerable media coverage, as it is strong evidence that the stories of Abraham, Jacob, Esau, and Joseph were written after this time. [84] [85]

The existence of camels in Mesopotamia—but not in the eastern Mediterranean lands—is not a new idea. The historian Richard Bulliet did not think that the occasional mention of camels in the Bible meant that the domestic camels were common in the Holy Land at that time. [86] The archaeologist William F. Albright, writing even earlier, saw camels in the Bible as an anachronism. [87]

The official report by Sapir-Hen and Ben-Joseph notes:

The introduction of the dromedary camel (Camelus dromedarius) as a pack animal to the southern Levant . substantially facilitated trade across the vast deserts of Arabia, promoting both economic and social change (e.g., Kohler 1984 Borowski 1998: 112–116 Jasmin 2005). This . has generated extensive discussion regarding the date of the earliest domestic camel in the southern Levant (and beyond) (e.g., Albright 1949: 207 Epstein 1971: 558–584 Bulliet 1975 Zarins 1989 Köhler-Rollefson 1993 Uerpmann and Uerpmann 2002 Jasmin 2005 2006 Heide 2010 Rosen and Saidel 2010 Grigson 2012). Most scholars today agree that the dromedary was exploited as a pack animal sometime in the early Iron Age (not before the 12th century [BC])

Current data from copper smelting sites of the Aravah Valley enable us to pinpoint the introduction of domestic camels to the southern Levant more precisely based on stratigraphic contexts associated with an extensive suite of radiocarbon dates. The data indicate that this event occurred not earlier than the last third of the 10th century [BC] and most probably during this time. The coincidence of this event with a major reorganization of the copper industry of the region—attributed to the results of the campaign of Pharaoh Shoshenq I—raises the possibility that the two were connected, and that camels were introduced as part of the efforts to improve efficiency by facilitating trade. [85]

A camel serving as a draft animal in Pakistan (2009)

A camel in a ceremonial procession, its rider playing kettledrums, Mughal Empire (c. 1840)

Petroglyph of a camel, Negev, southern Israel (prior to c. 5300 BC)

Joseph Sells Grain by Bartholomeus Breenbergh (1655), showing camel with rider at left

Textiles

Desert tribes and Mongolian nomads use camel hair for tents, yurts, clothing, bedding and accessories. Camels have outer guard hairs and soft inner down, and the fibers are sorted [ by whom? ] by color and age of the animal. The guard hairs can be felted for use as waterproof coats for the herdsmen, while the softer hair is used for premium goods. [88] The fiber can be spun for use in weaving or made into yarns for hand knitting or crochet. Pure camel hair is recorded as being used for western garments from the 17th century onwards, and from the 19th century a mixture of wool and camel hair was used. [89]

Military uses

By at least 1200 BC the first camel saddles had appeared, and Bactrian camels could be ridden. The first saddle was positioned to the back of the camel, and control of the Bactrian camel was exercised by means of a stick. However, between 500 and 100 BC, Bactrian camels came into military use. New saddles, which were inflexible and bent, were put over the humps and divided the rider's weight over the animal. In the seventh century BC the military Arabian saddle evolved, which again improved the saddle design slightly. [90] [91]

Military forces have used camel cavalries in wars throughout Africa, the Middle East, and into the modern-day Border Security Force (BSF) of India (though as of July 2012, the BSF planned the replacement of camels with ATVs). The first documented use of camel cavalries occurred in the Battle of Qarqar in 853 BC. [92] [93] [94] Armies have also used camels as freight animals instead of horses and mules. [95] [96]

The East Roman Empire used auxiliary forces known as dromedarii, whom the Romans recruited in desert provinces. [97] [98] The camels were used mostly in combat because of their ability to scare off horses at close range (horses are afraid of the camels' scent), [19] a quality famously employed by the Achaemenid Persians when fighting Lydia in the Battle of Thymbra (547 BC). [54] [99] [100]

19th and 20th centuries

The United States Army established the U.S. Camel Corps, stationed in California, in the late 19th century. [19] One may still see stables at the Benicia Arsenal in Benicia, California, where they nowadays serve as the Benicia Historical Museum. [101] Though the experimental use of camels was seen as a success (John B. Floyd, Secretary of War in 1858, recommended that funds be allocated towards obtaining a thousand more camels), the outbreak of the American Civil War in 1861 saw the end of the Camel Corps: Texas became part of the Confederacy, and most of the camels were left to wander away into the desert. [96]

France created a méhariste camel corps in 1912 as part of the Armée d'Afrique in the Sahara [102] in order to exercise greater control over the camel-riding Tuareg and Arab insurgents, as previous efforts to defeat them on foot had failed. [103] The Free French Camel Corps fought during World War II, and camel-mounted units remained in service until the end of French rule over Algeria in 1962. [104]

In 1916, the British created the Imperial Camel Corps. It was originally used to fight the Senussi, but was later used in the Sinai and Palestine Campaign in World War I. The Imperial Camel Corps comprised infantrymen mounted on camels for movement across desert, though they dismounted at battle sites and fought on foot. After July 1918, the Corps began to become run down, receiving no new reinforcements, and was formally disbanded in 1919. [105]

In World War I, the British Army also created the Egyptian Camel Transport Corps, which consisted of a group of Egyptian camel drivers and their camels. The Corps supported British war operations in Sinai, Palestine, and Syria by transporting supplies to the troops. [106] [107] [108]

The Somaliland Camel Corps was created by colonial authorities in British Somaliland in 1912 it was disbanded in 1944. [109]

Bactrian camels were used by Romanian forces during World War II in the Caucasian region. [110] At the same period the Soviet units operating around Astrakhan in 1942 adopted local camels as draft animals due to shortage of trucks and horses, and kept them even after moving out of the area. Despite severe losses, some of these camels came as far West as to Berlin itself. [111]

The Bikaner Camel Corps of British India fought alongside the British Indian Army in World Wars I and II. [112]

The Tropas Nómadas (Nomad Troops) were an auxiliary regiment of Sahrawi tribesmen serving in the colonial army in Spanish Sahara (today Western Sahara). Operational from the 1930s until the end of the Spanish presence in the territory in 1975, the Tropas Nómadas were equipped with small arms and led by Spanish officers. The unit guarded outposts and sometimes conducted patrols on camelback. [113] [114]

Food uses

Dairy

Camel milk is a staple food of desert nomad tribes and is sometimes considered a meal itself a nomad can live on only camel milk for almost a month. [19] [40] [115] [116]

Camel milk can readily be made into yogurt, but can only be made into butter if it is soured first, churned, and a clarifying agent is then added. [19] Until recently, camel milk could not be made into camel cheese because rennet was unable to coagulate the milk proteins to allow the collection of curds. [117] Developing less wasteful uses of the milk, the FAO commissioned Professor J.P. Ramet of the École Nationale Supérieure d'Agronomie et des Industries Alimentaires, who was able to produce curdling by the addition of calcium phosphate and vegetable rennet in the 1990s. [118] The cheese produced from this process has low levels of cholesterol and is easy to digest, even for the lactose intolerant. [119] [120]

Camel milk can also be made into ice cream. [121] [122]

They provide food in the form of meat and milk. [123] Approximately 3.3 million camels and camelids are slaughtered each year for meat worldwide. [124] A camel carcass can provide a substantial amount of meat. The male dromedary carcass can weigh 300–400 kg (661–882 lb), while the carcass of a male Bactrian can weigh up to 650 kg (1,433 lb). The carcass of a female dromedary weighs less than the male, ranging between 250 and 350 kg (550 and 770 lb). [18] The brisket, ribs and loin are among the preferred parts, and the hump is considered a delicacy. [125] The hump contains "white and sickly fat", which can be used to make the khli (preserved meat) of mutton, beef, or camel. [126] On the other hand, camel milk and meat are rich in protein, vitamins, glycogen, and other nutrients making them essential in the diet of many people. From chemical composition to meat quality, the dromedary camel is the preferred breed for meat production. It does well even in arid areas due to its unusual physiological behaviors and characteristics, which include tolerance to extreme temperatures, radiation from the sun, water paucity, rugged landscape and low vegetation. [127] Camel meat is reported to taste like coarse beef, but older camels can prove to be very tough, [13] [18] although camel meat becomes tenderer the more it is cooked. [128] The Abu Dhabi Officers' Club serves a camel burger mixed with beef or lamb fat in order to improve the texture and taste. [129] In Karachi, Pakistan, some restaurants prepare nihari from camel meat. [130] Specialist camel butchers provide expert cuts, with the hump considered the most popular. [131]

Camel meat has been eaten for centuries. It has been recorded by ancient Greek writers as an available dish at banquets in ancient Persia, usually roasted whole. [132] The Roman emperor Heliogabalus enjoyed camel's heel. [40] Camel meat is mainly eaten in certain regions, including Eritrea, Somalia, Djibouti, Saudi Arabia, Egypt, Syria, Libya, Sudan, Ethiopia, Kazakhstan, and other arid regions where alternative forms of protein may be limited or where camel meat has had a long cultural history. [18] [40] [125] Camel blood is also consumable, as is the case among pastoralists in northern Kenya, where camel blood is drunk with milk and acts as a key source of iron, vitamin D, salts and minerals. [18] [125] [133]

A 2005 report issued jointly by the Saudi Ministry of Health and the United States Centers for Disease Control and Prevention details four cases of human bubonic plague resulting from the ingestion of raw camel liver. [134]

Australia

Camel meat is also occasionally found in Australian cuisine: for example, a camel lasagna is available in Alice Springs. [132] [133] Australia has exported camel meat, primarily to the Middle East but also to Europe and the US, for many years. [135] The meat is very popular among North African Australians, such as Somalis, and other Australians have also been buying it. The feral nature of the animals means they produce a different type of meat to farmed camels in other parts of the world, [136] and it is sought after because it is disease-free, and a unique genetic group. Demand is outstripping supply, and governments are being urged not to cull the camels, but redirect the cost of the cull into developing the market. Australia has seven camel dairies, which produce milk, cheese and skincare products in addition to meat. [137]

Religion

Islam

Camel meat is halal (Arabic: حلال ‎, 'allowed') for Muslims. However, according to some Islamic schools of thought, a state of impurity is brought on by the consumption of it. Consequently, these schools hold that Muslims must perform wudhu (ablution) before the next time they pray after eating camel meat. [138] Also, some Islamic schools of thought consider it haram (Arabic: حرام ‎, 'forbidden') for a Muslim to perform Salat in places where camels lie, as it is said to be a dwelling place of the Shaytan (Arabic: شيطان ‎, 'Devil'). [138] According to Abu Yusuf, the urine of camel may be used for medical treatment if necessary, but according to Abū Ḥanīfah, the drinking of camel urine is discouraged. [139]

The Islamic texts contain several stories featuring camels. In the story of the people of Thamud, the Prophet Salih miraculously brings forth a naqat (Arabic: ناقة ‎, 'she-camel') out of a rock. After the Prophet Muhammad migrated from Mecca to Medina, he allowed his she-camel to roam there the location where the camel stopped to rest determined the location where he would build his house in Medina. [140]

Judaism

According to Jewish tradition, camel meat and milk are not kosher. [141] Camels possess only one of the two kosher criteria although they chew their cud, they do not possess cloven hooves: "But these you shall not eat among those that bring up the cud and those that have a cloven hoof: the camel, because it brings up its cud, but does not have a [completely] cloven hoof it is unclean for you." [142]

Depictions in culture

Shadda (cover,detail), Karabagh region, southwest Caucasus, early 19th century

Vessel in the form of a recumbent camel with jugs, 250 BC – 224 AD, Brooklyn Museum

Maru Ragini (Dhola and Maru Riding on a Camel), c. 1750, Brooklyn Museum

The Magi Journeying (Les rois mages en voyage)—James Tissot, c. 1886, Brooklyn Museum

There are around 14 million camels alive as of 2010 [update] , with 90% being dromedaries. [143] Dromedaries alive today are domesticated animals (mostly living in the Horn of Africa, the Sahel, Maghreb, Middle East and South Asia). The Horn region alone has the largest concentration of camels in the world, [22] where the dromedaries constitute an important part of local nomadic life. They provide nomadic people in Somalia [18] and Ethiopia with milk, food, and transportation. [116] [144] [145] [146]

Around 700,000 dromedary camels are now feral in Australia, descended from those introduced as a method of transport in the 19th and early 20th centuries. [133] [143] [147] This population is growing about 8% per year. [148] Representatives of the Australian government have culled more than 100,000 of the animals in part because the camels use too much of the limited resources needed by sheep farmers. [149]

A small population of introduced camels, dromedaries and Bactrians, wandered through Southwestern United States after having been imported in the 19th century as part of the U.S. Camel Corps experiment. When the project ended, they were used as draft animals in mines and escaped or were released. Twenty-five U.S. camels were bought and exported to Canada during the Cariboo Gold Rush. [96]

The Bactrian camel is, as of 2010 [update] , reduced to an estimated 1.4 million animals, most of which are domesticated. [43] [143] [150] The Wild Bactrian camel is a separate species and is the only truly wild (as opposed to feral) camel in the world. The wild camels are critically endangered and number approximately 1400, inhabiting the Gobi and Taklamakan Deserts in China and Mongolia. [12] [151]


The Strangest, Most Amazing Lactation Methods Ever Seen in Mammals

I should explain that I’m talking about her mammary glands, in particular. (All mammals have mammary glands, though not all mammals have breasts. Some of them don’t even have nipples. But we’ll get to that.)

A few weeks ago, my wife and I welcomed our second child into the world—a wee little squeaker named June. After nearly nine months of sipping her meals through a straw in her belly, this bitty baby popped out, threw some shade at the doctor, and immediately began to suckle from my wife’s breast.

And I guess that’s when it struck me—not only did my wife’s body just funnel all of its resources into the creation of this animal, rearranging organs and increasing its blood supply by 50 percent in the process, but once it had expelled her, my wife’s body shifted modes like a Transformer to further accommodate its mewling creation.

In the hours and days to come, my daughter’s near-constant stimulation would trigger hormones to wash over my wife’s body, initiating lactation. Her mammary glands would produce colostrum, a concentrated proto-milk full of immune cells, antibodies, and protein that kick-starts the infant’s digestion and growth. The colostrum would give way to a more regular supply of milk composed of thousands of bioactive molecules that ward off infection, prevent inflammation, promote immunity, spur organ development, and cultivate a healthy microbiome.

My wife’s body would produce just as much milk as my daughter could drink, replenishing the supply in between feedings, and tweaking the recipe as the baby grew. Human milk is made to order depending on the time of day, the length of the feed, and the diet of the mother.

Like I said: absolutely sucking amazing.

So in honor of my daughter, my wife, and amazing mammary glands, I did some digging into the wonder that is mammalian lactation.

More than 200 million years before the “Got Milk?” campaign, the first mammals crawled onto the scene. Mammary glands are the main unifier of all us mammals—from moles, dogs, and koalas to tigers, lemurs, and platypuses.

“There are over 5,600 species of mammal, probably closer to 6,000 once they all get described, and they all start life on a diet of milk,” says George Feldhamer, professor emeritus at Southern Illinois University and author of the widely used textbook Mammalogy. But as Feldhamer points out, lactation can differ greatly among those of us in the milk-maker tribe.

Human milk, for instance, is a watery brew with just 3.8 percent fat and 1.2 percent protein. Compare that with the milk of a blue whale, which is 38.1 percent fat and 12.8 percent protein. Blue whale milk has the consistency of “loose, runny cheese” and smells like it was made in a Bass-O-Matic.

As the largest creatures to ever live, blue whales also hold the record for the biggest bazookas—each mammary gland is nearly 5 feet long and weighs almost 250 pounds. Like humans, blue whales have two such glands, which means each adult female is carrying around a quarter of a ton of milk-producing machinery. Of course, all this milk-making power is what helps the blue whale calf pack on 37,500 pounds during its suckling period.

But the leviathans aren’t even the fattiest milk producers in the animal kingdom. That prize goes to hooded seals. Their milk can reach 61 percent fat, a richness even Paula Deen would find excessive.

But decadence in nature is never needless—hooded seal mothers nurse their pups for just four days on pack ice before returning to the sea to find food. This is the shortest lactation period of any mammal. That means the pups must pack on as much weight as possible, as quickly as possible, or die alone on the ice. Drinking nearly 45,000 calories of liquid butter each day is the only way such an arrangement can work.

While we’re talking about marine mammals, I should probably clarify that neither seals nor whales are swimming around with anything resembling cleavage. All marine mammals lack breasts as we know them and keep their working parts inside the body proper.

The pinnipeds (seals, sea lions, and walruses) have retractable nipples, which sounds like a burn straight out of the junior-high locker room but in truth just means the nipples tuck inside when they’re not in use. This likely cuts down on drag in the water and protects the tidbits from the cold.

The cetaceans (whales, dolphins, porpoises, narwhals, and the like) take this trick a step further by burying their nursing parts below a fold of skin called the “mammary slit.” These nipple-housing envelopes are found on either side of another, longer slit, which contains the genitals.

Because dolphins and whales don’t really have lips like most mammals, it’s been posited that the mother’s abdominal muscles actually squeeze the mammary glands and eject milk into the calf’s mouth. There’s some evidence that the babies can assist the process by curling their tongues into troughs, the better to create suction and gulp down their liquid lunches.

Of all the sucklers though, opossums are the most committed. Following a gestation period of just 12 days, baby opossums emerge from their mother’s vaginas blind, deaf, naked, and with brains that are only 9 percent developed, which isn’t much of a brain even for an opossum. About the only thing these marsupials have going for them is a massive set of claws, which they use to climb up the mother’s body and into her pouch. Once inside, those who find a teat latch on and don’t let go for two straight months.

The nipples swell inside the babies’ mouths, creating a lock so tight that scientists have found that trying to forcefully separate a baby from its mother can result in torn lips and nips. (I think I just heard my wife shudder from the next room.)

Over the course of 60 days, the opossum’s nipple will stretch and grow up to 35 times its original length. This creates a tether between mother and child not unlike an umbilical cord and every bit as vital. A baby opossum that does not find a nipple after birth will be dead in minutes. And the same goes for any offspring that become detached before they’re ready to wean.

Nipples—what strange little bio-valves they are. For all the time we spend talking about nip slips and Instagram’s nipple censorship policies, we pay scarcely little attention to the wild nipples all around us.

According to the 2015 edition of Guinness World Records, the animal with the most nipples is the female shrewish short-tailed opossum, which can boast a 27-gun salute. When scientists dart and collar female polar bears, they can determine an approximate age by nipple size, since the teats get longer and wider as the animals become teenagers. Kangaroos nurse two different generations of joeys at a time, which means one nipple is devoted to carbohydrate-rich milk for the neonate in its pouch and another nipple delivers fat-rich milk for the yearling living outside. (Kangaroos are baby-making machines.)

In porcupines, bleached fur around the nipples is proof that the female has reared young in the past. Uldis Roze, porcupine expert and author of The North American Porcupine tells me that porcupettes (really, that’s what they’re called) have also been documented to play a little game of Simon with their mother’s nipples. They first tug at one nipple, then another, then another, suckling milk from each gland in an order that they will repeat throughout their nursing months.

Anyone who has owned a cat or dog knows that nipple placement also varies throughout Mammalia. Ours are near our armpits, as are elephants’. But many other animals—cows, squirrels, giraffes—keep theirs toward the hindquarters.

And then there are bats. Bats are already pretty special when it comes to mammals, because they’re the only ones that said, “Eff it, we’re conquering the sky!” Bats also have fascinating sex lives. So perhaps it’s not so surprising that they have awesome nipples.

Like us, bats nurse from teats on the upper body. But reports kept coming in over the years from scientists seeing another set of nipples located down on the pelvis of some species. In many cases, the “pubic teats” did not seem to be attached to functioning mammary glands. So what possible purpose could these extra nipples serve? Oh, an awesome one.

Pubic teats “are used as devices for the young to hold onto when the mother is flying,” says Nancy Simmons, curator-in-charge of mammals at the American Museum of Natural History.

The pup simply latches onto the mom’s pubic teat, wraps its legs around her neck like it’s doing a reverse-hurricanrana, and then the two fly off into the night.

All of this is described in Simmons’ 1993 paper in which she examined the nipples on 1,723 bat specimens representing 206 species. Her work remains the definitive word on bat nipples—which one can only hope affords her plenty of free drinks in every bar on Earth.

While we’re talking about lactating Chiropterans, I should at least mention that the only male mammal that has been shown to produce milk in the wild is also a bat.

Dayak fruit bats captured in Malaysia have been shown to express a relatively small amount of what appears to be milk. However, before you start lauding these guys for being some sort of male milk nurses, I should also say that there’s no evidence that they help nurse the pups. And their drippy nips may be more of an effect of their diet than some sort of evolutionary advance.

“It is likely that Dayak fruit bats ate leaves or fruits containing plant estrogens, which stimulated their mammary tissue, which then produced some secretion,” says Paul Racey, professor emeritus at the University of Aberdeen and author of a dissenting opinion on whether male bats truly lactate.

Whatever the case, there’s a yet more impressive feat than males making use of their nipples—and that’s nursing young without any nipples at all.

I refer of course to the monotremes, the only mammals left alive that lay eggs.

Photo by ROMEO GACAD/AFP/Getty Images

“The platypus and echidnas don’t actually have nipples,” says Feldhamer. “They have mammary glands, they secrete milk, but it just drips out onto tufts of fur.”

Still, there’s a lot to be said in support of nipples. In addition to guiding the milk directly into the baby’s yawning maw, nipples minimize the milk’s exposure to microbes. Perhaps this is why scientists have found the presence of an antibacterial agent that occurs exclusively in monotreme milk.

This is far from an exhaustive list of everything interesting about mammalian lactation. The Stejneger’s beaked whale, for instance, has milk that’s blue-green in color. Rodents and many other mammals (including humans) tend to have half as many offspring per brood as they do nipples. The dwarf mongooses of Tanzania are one of the only wild mammals in which females that have never been pregnant will spontaneously lactate to cooperatively care for other young in the pack.

Every way you look at it, lactation is biological alchemy. That jug of cow’s milk in your fridge or breast milk in the freezer? It’s evolution in a bottle.


Characteristics of Mammals

Two characteristics are used to define the mammal class. They are mammary glands and body hair (or fur).

  1. Female mammals have mammary glands. The glands produce milk after the birth of offspring. Milk is a nutritious fluid. It contains disease-fighting molecules as well as all the nutrients a baby mammal needs. Producing milk for offspring is called lactation.
  2. Mammals have hair or fur. It insulates the body to help conserve body heat. It can also be used for sensing and communicating. For example, cats use their whiskers to sense their surroundings. They also raise their fur to look larger and more threatening (see Figurebelow).

Cat Communicating a Warning. By raising its fur, this cat is &ldquosaying&rdquo that it&rsquos big and dangerous. This might discourage a predator from attacking.

Most mammals share several other traits. The traits in the following list are typical of, but not necessarily unique to, mammals.

  • The skin of many mammals is covered with sweat glands. The glands produce sweat, the salty fluid that helps cool the body.
  • Mammalian lungs have millions of tiny air sacs called alveoli. They provide a very large surface area for gas exchange.
  • The heart of a mammal consists of four chambers. This makes it more efficient and powerful for delivering oxygenated blood to tissues.
  • The brain of a mammal is relatively large and has a covering called the neocortex. This structure plays an important role in many complex brain functions.
  • The mammalian middle ear has three tiny bones that carry sound vibrations from the outer to inner ear. The bones give mammals exceptionally good hearing. In other vertebrates, the three bones are part of the jaw and not involved in hearing.
  • Mammals have four different types of teeth. The teeth of other vertebrates, in contrast, are all alike.

Dolphins are mammals that have adapted to swimming and reproducing in water.


How human breast milk compares to other mammals

All mammals feed their young with their mammary glands, known to us as breasts, though the makeup of that milk varies depending on the animal, Sinnott says. While human newborns are dependent on their caregivers for everything, other mammals must run or walk hours after birth, so their composition of milk is different.

For example, cow's milk contains more protein and fat than human milk because calves must walk soon after birth and follow their mothers for food and protection. Human babies, on the other hand, are the most immature mammals at birth, and they must be fed frequently, so human milk contains lower levels of protein and fat, Sinnott says.


Composition and properties of milk

Milk can be regarded as an emulsion of fat globules in a colloidal solution of protein together with other substances in true solution. Two constituents of milk—the protein casein and milk sugar, or lactose—are not found elsewhere in the body.

Breastfeeding is particularly advantageous because of the nutritional, immunologic, and psychological benefits. Human breast milk is superior to modified cow’s milk formulas, which may lack essential and beneficial components and are not absorbed as easily or as quickly by the infant. Maternal breast milk provides vitamins, minerals, protein, and anti-infectious factors antibodies that protect the infant’s gastrointestinal tract are supplied, resulting in a lower rate of enteric infection in breast-fed than in bottle-fed babies. The bonding that is established through breast-feeding is advantageous to building the parent-child relationship.

The nutritional status of the mother is important throughout this period. The mother’s daily caloric intake must increase significantly in order to replenish the mother’s nutrient and energy stores. The use of drugs or smoking by the mother can adversely affect the infant many drugs are secreted in breast milk, and smoking reduces breast milk volume and decreases infant growth rates.

The milk released from the breast when lactation starts differs in composition from the mature milk produced when lactation is well established. The early milk, or colostrum, is rich in essential amino acids, the protein building blocks essential for growth it also contains the proteins that convey immunity to some infections from mother to young, although not in such quantity as among domestic animals. The human infant gains this type of immunity largely within the uterus by the transfer of these antibody proteins through the placenta the young baby seldom falls victim to mumps, measles, diphtheria, or scarlet fever. For a short time after birth, proteins can be absorbed from the intestine without digestion, so that the acquisition of further immunity is facilitated. The growth of harmful viruses and bacteria in the intestines is probably inhibited by immune factors in human milk. After childbirth the composition of milk gradually changes within four or five days the colostrum has become transitional milk, and mature milk is secreted some 14 days after delivery.

Some variations between human colostrum, transitional milk, and mature milk and cow’s milk are shown in Table 2. The greater amount of protein in unmodified cow’s milk is largely responsible for its dense, hard curd, which the infant cannot digest the difficulty can be avoided by heat treatment or dilution of the milk. Ordinarily, when cow’s milk is fed to young infants, it is modified so as to match its composition as far as possible to breast milk.

Some constituents of human colostrum, transitional, and mature milk and of cow's milk
(average values per 100 millilitres whole milk)
colostrum (1–5 days) transitional (6–14 days) mature (after 14 days) cow's milk
*Kilocalorie sufficient energy to raise the temperature of 1 kilogram of water 1 degree Centigrade.
energy, kcal* 58 74 71 69
total solids, g 12.8 13.6 12.4 12.7
fat, g 2.9 3.6 3.8 3.7
lactose, g 5.3 6.6 7.0 4.8
protein, g 2.7 1.6 1.2 3.3
casein, g 1.2 0.7 0.4 2.8
ash, g 0.33 0.24 0.21 0.72
calcium, mg 31 34 33 125
magnesium, mg 4 4 4 12
potassium, mg 74 64 55 138
sodium, mg 48 29 15 58
iron, mg 0.09 0.04 0.15 0.10

The annual impact from eating a specific food is calculated by multiplying the impact of one serving of that food by the times it is eaten in a year, based on the weekly estimates submitted by the user.

These are then compared with the emissions of other daily habits. The European Environment Agency estimates that driving a regular petrol car produces 392g of CO2eq/mile over its entire lifecycle, including emissions from the vehicle's production, fuel production and exhaust emissions per mile.

Heating the average UK home produces 2.34 tonnes of CO2eq annually, according to data from the Committee on Climate Change, and a passenger's carbon footprint for a return flight from London to Malaga is 320kg CO2eq, based on figures from the Carbon Neutral calculator.

The land used to produce the annual consumption of each food is compared with the size of a double tennis court, 261 metres squared.

The annual amount of water used is compared with a shower, based on figures suggesting the average shower lasts eight minutes and uses up 65 litres. Only "blue water", i.e. water taken out of rivers or the ground, is included in the data.

Update 22nd February 2019: This article has been updated to include more detail about the methodology used. A chart has also been added showing the environmental impact of cow's milk, broken down by region.