Manatee FAQ: Anatomy and
Physiology
Q. Is it true that manatees
actually have fingernails?
(Click link to get the answer)
Q. About how fast do manatees grow, and at what age do they stop?
(Click link to
get answer)
Q. I have heard that adult female manatees are larger than adult males. Is this true and, if so, is it known why?
(Click link to
get answer)
Q. Are the manatees in Belize the same species found in
Florida? What are the other different types of manatee species around the
world? (Click link to get answer)
Q. Are manatees color blind? (Click link to
get answer)
Q. Do
manatees sweat? (Click link to get answer)
Q. Do manatees have good eyesight?
A. Surprisingly enough, manatees have fairly good visual acuity
and can distinguish between different-sized objects, different colors,
and patterns. Their eyes are small, and they have a nictitating membrane
that can be drawn across the eyeball for protection.
Q. How do manatees communicate with each
other,
and do they hear very well?
A. On the
whole, the sensory systems of the manatee have not been well studied.
Anatomically, manatees have extremely large ear bones and may have a good
sense of hearing. Manatees emit sounds underwater that are used in
communicating with one another. It is not believed they are used for
navigational purposes. Vocalizations may express fear, anger, or sexual
arousal. They are also used to maintain contact, especially when manatees
are feeding or traveling in turbid water. Especially common are
vocalizations between a female and calf.
Manatee sounds can be described as chirps, whistles or squeaks, have
peak energies in the 3-5 kilohertz range, and are probably produced in
the larynx. It has been suggested, but not confirmed, that the most
sensitive location on the manatee's head for sound reception is not the
tiny ear openings located several centimeters behind the eyes, but the
area near the cheek bones, which are large and seem to be quite oily
compared with other bones in the skull and which are in direct contact
with the ear bones. This arrangement is similar to that of dolphins.
In addition, anatomical studies suggest that manatees
are not adapted to hear infrasound, frequencies too low to be heard by
the human ear, generally less than 20 hertz.
Q. What is the
“peduncle” of a manatee?
A. The peduncle is the base of the tail, right where it connects
to the body of the manatee.
Q. What is the average weight of a
manatee?
A. The average adult manatee is about three meters (9.8 feet) long
and weighs between 362-544 kilograms (800-1,200) pounds.
Q. What is the record weight of a
manatee?
A. Adult manatees have been known to exceed lengths of near four
meters (13 feet) and weigh over 1,587 kilograms (3,500 pounds).
Q. What is the record age of a
manatee?
A. Scientists believe that manatees are capable of living for 60
years or more. One manatee living in captivity, Snooty, is now over 50
years old. We know how old he is because he was born in captivity
in 1948. Unless you know when a manatee is born, the only way to
determine their age is by counting growth layer rings in their ear
bones. Obviously this can only happen after a manatee has
died.
Q. How can you tell a female from a male
manatee?
A. If you look at the underside of a manatee, referencing from the
head to the tail, the genital opening in the male manatee is just below
the umbilicus (belly button), and the female's genital opening is just
above the anus. That's how you can tell a female from a male.
Q. Do
manatees have teeth? (click link to get answer)
Q. How do people tell manatees
apart?
A. Sadly enough, most adult manatees living in the wild bear scars
from at least one watercraft collision. In fact, manatee scars are so
commonplace, researchers use them as a method of individual
identification.
Q. What are the kinds and sizes of manatee boat
scars? Are any scars curable, or do they stay on the manatees
forever?
A. Many manatees have "skeg" marks. A skeg is part of a motor on
the boat. It extends slightly below the propeller and can sometimes come
in contact with the manatee without the propeller making contact,
creating a single longitudinal gash. When a manatee gets hit by a boat
propeller, it also creates prop wounds which take the form of a parallel
series of slash marks. If the injury is deep enough, it can be seen on
the manatee forever. If the injury is superficial, it will still be
there, but you wouldn't be able to see it unless you got very close as
skin would grow on top of it.
Q. Does a manatee's skin ever change
color?
A. When manatees are born, they are a gray-black in color. Within
a month they change to gray. Manatee adults range in color from gray to
brownish-gray.
Q. What is the “green stuff” you see
on their bodies?
A. Manatees that are found in fresh water often have algae growing
on their backs. Manatees that are found in salt water sometimes will have
barnacles attached to them -- just like boats found in those
waters!
Q. What is the purpose of a manatee's
whiskers?
A. Although the exact purpose is not clear, it is thought the
“vibrisae” or whiskers on a manatee’s snout are sensory
in function. Researchers have discovered that each whisker has a nerve
connection to a small cluster of cells in the manatee’s brain
devoted exclusively to that whisker! Further research may solve more of
these mysteries.
Q. Do manatees have blowholes?
A. Manatees do not have blowholes. They breathe through
nostrils, like seals. Their nostrils have fleshy "valves" that close when
they are underwater.
Q. Why can't manatees adapt well to cold
water?
A. Modern manatees evolved in the tropics and subtropics. In spite
of their size, they have very little body fat. These factors may account
for their susceptibility to cold water. Because manatees are herbivores,
their metabolic rate is low compared with other aquatic
mammals.
Q. How can manatees go such a long period of
time without taking a breath?
A. Manatees, like other aquatic mammals, do most of their feeding
underwater and must be able to hold their breath long enough to feed
efficiently. Aquatic mammals have a number of adaptations that allow them
to stay under water longer than the average land-dwelling mammal. Both
the lungs and diaphragm of a manatee extend the length of the body cavity
and so are oriented in the same horizontal plane as the manatee in the
water. This arrangement is important for buoyancy control. An unusual
anatomical feature of sirenians is that each lung is in a separate
cavity. Instead of one diaphram like people, manatees have separate
“hemi-diaphragms.” Besides breathing, the lungs help the
manatee with buoyancy control. Manatees replace a large percentage of air
in their lungs with each breath and can therefore prolong intervals
between breaths. In fact, studies have shown that manatees can renew
about 90% of the air in their lungs in a single breath as compared to
humans at rest who generally renew about 10%.
See anatomical drawings and read more about the
Internal Anatomy of the Florida
Manatee
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