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Uploaded:2016-05-09
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Learn some curious facts about the majestic manatee.

Hosted by: Hank Green
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Sources:
http://animaldiversity.org/accounts/Trichechidae/
http://www.smithsonianmag.com/science-nature/14-fun-facts-about-manatees-180950308/
http://www.livescience.com/27405-manatees.html
http://www.manateebrain.org/index.html
http://www.savethemanatee.org/faq_hair.html
http://www.nytimes.com/imagepages/2006/08/28/science/20060829_MANA_GRAPHIC.html
https://today.duke.edu/2013/10/whiskers
http://www.learner.org/jnorth/tm/manatee/AdaptationsHead.html
http://www.southfloridamuseum.org/TheAquarium/AboutManatees.aspx
http://news.nationalgeographic.com/news/2006/10/061020-manatees_2.html
http://www.nytimes.com/2006/08/29/science/29mana.html?pagewanted=all&_r=1&

Images:
Dugong: https://commons.wikimedia.org/wiki/File:Dugong_Marsa_Alam_PLW_edit.jpg
African Elephant: https://commons.wikimedia.org/wiki/File:African_Elephant_(Loxodonta_africana)_male_(16723147361).jpg
Rock Hyrax: https://commons.wikimedia.org/wiki/File:Yellow-spotted_Rock_Hyrax.jpg
Manatee Fingernails: https://commons.wikimedia.org/wiki/File:Trichechus_manatus_fg01.JPG
Mermaid: https://commons.wikimedia.org/wiki/File:Vilhelm_Pedersen-Little_mermaid.jpg
Manatee Eating: https://commons.wikimedia.org/wiki/File:Hpim0279.jpg
Manatees: https://commons.wikimedia.org/wiki/File:Manatee2.jpg
Manatees Clustering: https://commons.wikimedia.org/wiki/File:Manatee_animals.jpg
Cat Whiskers: https://commons.wikimedia.org/wiki/File:Animal_Abstract_Photo_(By_R.Boroujerdi).JPG
Manatee Whiskers: https://commons.wikimedia.org/wiki/File:Trichechus_manatus.jpg
Elephant Trunk: https://commons.wikimedia.org/wiki/File:Elephant_trunk_(1).jpg
Map Distribution of Manatees: https://commons.wikimedia.org/wiki/File:Mapa_distribuicao_Trichechus.png

[SciShow intro plays]

Hank: This is a manatee -- also sometimes called a sea cow. At first glance, you might think the three species of manatee, along with the closely related dugong, are related to seals or walruses. But their closest living relatives are actually elephants and small, stocky hyraxes. Some species even have fingernails on their flippers, old souvenirs from their ancient days on land.

They live in shallow coastal waters and rivers in tropical areas, and some historians think that some of the old mermaid legends came from really, really lonely sailors mistaking potatoey gray manatees for fish-tailed hot girls.

But even though they aren’t quite mermaids, manatees do have a special set of adaptations that help them get through life. Because it turns out that it isn’t always easy being a sea cow. For one thing, they have to keep growing new teeth. Manatees are herbivores, and eat mostly seagrass and other salt- and freshwater vegetation. And it takes a lot of food to maintain a 3 meter, 500 kilogram body, so, like other large vegetarians, these gentle giants spend a lot of their time foraging.

Because grass salad isn’t exactly packed with calories, manatees need to consume around ten percent of their body weight every day, so, around 50 kilograms, just to maintain that weight. Many of the plants they eat are abrasive and spiced only with sand, and the manatee's constant need to feed quickly wears down their teeth.

Luckily, they can avoid toothless starvation by just growing new ones. As the teeth near the front of the manatee’s jaw wear down and eventually fall out, they’re replaced by so-called “marching molars,” which start out at the back of the jaw and then slowly move forward. This type of conveyor belt tooth replacement is called polyphyodonty, and it's rare in mammals. Only manatees, kangaroos, and elephants have it.

Manatees can afford to eat this poor diet because they have no natural predators, so they’re cool with just slowly bobbing along and munching all day. But they do have to worry about the cold. It takes a heroic digestive system to process all that rough vegetation, so a big part of a manatee’s body is pure guts, and they’ve got a very low metabolism.

Although they look roly-poly and wrapped in blubber, compared with other aquatic mammals, manatees actually have very little body fat. This is in part because of their poor diet, but also because their warm water environments usually keep them warm enough they don’t need that extra fluff. And yet, it’s this lack of insulation that makes them quite sensitive to cold water and seasonal temperature changes.

Manatees are usually solitary animals, but during colder months, they sometimes cluster together in the warmer waters near power plants, or in the warmer parts of rivers. But sometimes even that isn’t enough -- like in 2010, when an unusually cold Florida winter killed hundreds of West Indian manatees. Their tendency to stay in shallow waters near humans also means that a lot of manatees are killed by boats.

When it comes to navigating through the water, though, manatees have a super useful advantage: their hair. They might look pretty bald, but manatees do have hair, just not a lot of it. But what they lack in quantity they make up for in quality. Manatee hair is thick and tactile,each one has its own personal nerve connection wired to the brain’s sensory cortex.

Like your cat’s whiskers, these tactile hairs can sense objects around them. Most other non-human mammals have a smattering of these specialized hairs on their heads and faces, but manatees sprout them all over their bodies. Biologists think that their 3,000 or so tactile body hairs help them navigate through shallow, murky waters, and even detect movement and vibrations.

They also have an additional 2,000 bristly face whiskers, which they use to feel out and even grasp foods while foraging. To help with that foraging, the right and left sides of their upper lips are prehensile, like the tip of an elephant’s trunk, and can move independently of one another to manipulate food. So, if you’re ever in their neighborhood, keep an eye out for manatees. They make for some pretty cool sea cows.

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