Do Manatees Get Cavities?
the Eating Habits of Manatees
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.
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.
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
To see (and
hear) more, watch the video clip below:
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.
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
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.
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?
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?
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.
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?
flippers and a split upper lip to migrating molars, manatees are perfectly
adapted for aquatic dining.
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