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Do Manatees Get Cavities?
Explore the Eating Habits of Manatees


Manatee feeding on the marine algae
Credit: USGS-Sirenia

Imagine canoeing down the St. John's River in Florida. Near the riverbank you spot a manatee grazing. Look closely at how the gentle giant pulls plants closer with its front flippers. Do you see the stiff, bristle-like hairs covering the manatee's lips? What else is unique about the manatee's large lips? How do the manatee's bristly lips maneuver plants into its mouth? What kind of teeth do manatees need to grind fibrous plants mixed with sand? In this article discover the physical characteristics that help manatees feed on floating and submerged vegetation.

What's On the Menu?
Manatees feed almost exclusively on plants that grow in fresh and saltwater environments. Freshwater plants include floating hyacinth, pickerelweed, alligator weed, water lettuce, hydrilla, water celery, and musk grass. Saltwater plants include sea grasses, shoal grass, manatee grass, turtle grass, widgeon grass, sea clover, and marine algae.

On average, a manatee feasts on 100-200 pounds of soggy, sandy sea grasses and weeds every day. The hearty herbivore grazes up to seven hours a day, consuming an amount of food equal to 10%-15% of its body weight. Do you think this grazing behavior is what earned this marine mammal the name, "sea cow?".

To see (and hear) more, watch the video clip below:

Hear the Crunching?

Photo Credit: FWC, Audio/Video Credit: SMC, International Film Projects,Inc

Flipper Food
How do manatees graze? Two front flippers pull or gather plants toward the manatee. Manatees also use their flippers to "walk" along the sandy bottom and to dig for roots in the mud. The flippers scoop the gritty vegetation and bring it toward the manatee's lips.

Split Upper Lip
The manatee has prehensile lips. The upper lip pad is split so that the left and right sides can move somewhat independently. The lips use seven distinct muscles to tear at plants. Front flippers and well-muscled, flexible lips guide the plants into the manatee's mouth.

Up On the Roof
The manatee does not have front teeth to cut down plants into small pieces. How does the manatee eat without front teeth? Right behind the lips, on the roof of the mouth, a manatee has dense, ridged pads. These horny ridges, and the manatee's lower jaw, tear through sea grasses. Bite-size morsels are sent to the manatee's teeth for grinding.

Four Sets of Six (Or Seven Or Eight)
What kind of teeth does a manatee need to grind grasses? The manatee's jawbone contains enamel-crowned molars. Manatees have four rows of teeth. There are 6 to 8 high-crowned, open-rooted molars located along each side of the upper and lower jaw. With their twenty-four to thirty-two flat, rough-textured teeth, the manatee chews and grinds gritty vegetation. How do you think a manatee's feeding habits affect its teeth? What happens when abrasive, sandpapery sea grasses wear away the manatee's molars? Do manatees have strong, wear-resistant enamel covering their teeth? Research suggests that manatee molars are weak in enamel structure. What adaptation evolved to help manatees munch on sand-filled vegetation that wears away their teeth?

Lifetime Supply
Scientists discovered that manatee teeth are disposable. Manatee teeth are continually replaced. Eating on gritty vegetation erodes the enamel crown of the molars. How does a manatee grow new teeth throughout its lifetime?

Marching Molars!
Anterior teeth sit in the front of the row. Posterior teeth sit in back. When anterior molars wear down from abrasive vegetation, the teeth are shed. Posterior molars erupt at the back of the row and slowly move forward. Manatee molars move forward horizontally along the jawline like enamel crowns on a conveyor belt. This process continues throughout the manatee's lifetime.

The rate at which the manatee's "marching molars" migrate forward along the jawbone depends on how quickly front row teeth wear out. Some studies indicate that the rate is about a centimeter per month. Other studies suggest the rate is about a millimeter per month. What do you think affects the rate at which molars march forward along the jaw? To investigate this molar mystery, think about the kinds of vegetation found in freshwater, brackish, and saltwater habitats. Which habitat do you think would have the most abrasive vegetation?

From fingerlike flippers and a split upper lip to migrating molars, manatees are perfectly adapted for aquatic dining.

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