| 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? |
| A.
|
They
do, and one of the interesting things about manatees is that
they have what is known as "marching molars." In
fact, molars are the only type of teeth that manatees have.
Their teeth are also unique because they are constantly replaced.
They form at the back of the jaw, wear down as they move forward,
and eventually fall out! Tooth replacement is an adaptation
to the manatee's diet of abrasive plants that are often mixed
with sand.
|
| 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%. |
