Is Hippo Milk Really Pink?
The pink hippo milk rumor has been spreading across the web for some time, but it really gained footing in 2013, when National Geographic posted about the hippo's rose-colored milk on both its Facebook and its Twitter pages. Is the rumor true? Let's examine the facts.
Do Hippos Produce Pink Milk?
Like all mammals, hippos (Hippopotamus amphibius) produce white or off-white milk for their babies.
Despite this fact, it's easy to see where some of the color confusion comes from. Hippos have no actual sweat glands, but they do have mucus glands, which release an oily secretion people frequently refer to as "blood sweat."
What Is Hippo Blood Sweat?
Despite its name, this secretion is neither blood nor sweat; instead, it's a blend of hipposudoric acid and norhipposudoric acid.
In combination, these two acids play an important role in the health of a hippopotamus. They serve as a natural form of sunscreen and moisturizer for the animal's sensitive skin, and they have antibiotic properties that protect hippos from harmful bacteria while they're in the water.
That means hippos can live in some pretty toxic spots with minimal risk of infection.
Now here's where it gets weird: This special secretion comes out colorless like human sweat, but it turns to a bright orange-red in the sun so that it looks like blood. A few hours later, it loses its blood-like luster and shifts into a dirty brown color.
Hippo Sweat Mixing With Hippo Milk: Common or Uncommon?
During the period that the hippo's secretions are at their orange-red peak, some could mix with the milk, giving it a pinkish hue.
While this is possible, it's also pretty unlikely, as baby hippos are very efficient eaters. A baby hippo grips its mother's nipple between the tongue and the roof of its mouth, forming such a tight bond that it can even nurse underwater if it wishes.
Reports of pink hippo milk are limited not only by the low odds that these two fluids will mingle, but also thanks to the difficulty of getting a close look at the hippo's feeding process. Female hippos are most likely to attack when they are pregnant or taking care of their young, and few people are brave enough to tangle with a mad 3,000-pound (1,361-kilogram) female hippo just to get a glimpse of her milk.
The Pink Milk Rumor Persists
Despite a lack of evidence to support the pink milk theory, this rumor continues to spread; thousands of people have liked this fun "fact" on National Geographic's Facebook page.
While countless commenters have expressed exasperation that such an esteemed source has helped to perpetuate this myth, truth-seekers can take comfort in the fact that the site's official hippopotamus page doesn't make any mention of bright pink milk.
Lots More Information
Sources
Hashimoto Kimiko, Saikawa, Yoko and Nakata, Masaya. "Studies on the Red Sweat of the Hippopotamus Amphibius." Journal of Pure and Applied Chemistry. 2007. (Oct. 15, 2014). http://pac.iupac.org/publications/pac/pdf/2007/pdf/7904x0507.pdf
Mason, Kassandra. "Hippopotamus Amphibius." University of Michigan Museum of Zoology. 2013. (Oct. 15, 2014). http://animaldiversity.ummz.umich.edu/accounts/Hippopotamus_amphibius/#reproduction
Ritchie, Mark."Do Hippopotamuses Actually Have Pink Sweat?" Scientific American. May 6, 2002. (Oct. 15, 2014). http://www.scientificamerican.com/article/do-hippopotamuses-actuall/
Wynick, David. "Ask a Biologist." Jan. 4, 2012. (Oct. 15, 2014). http://askabiologist.org.uk/answers/viewtopic.php?id=7675
Original article: Is Hippo Milk Really Pink?
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