Manatee FAQ: Anatomy and Physiology

Q. Do manatees make any audible sounds to communicate with each other, like dolphins?
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Q. Are there ways manatees are identified besides scar patterns?
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Manatees look really fat, but as they are not (after all, they feel the cold), is this "fattiness" actually muscles?
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Q. Are there any interesting facts about the manatee's lungs?
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Q. How long can manatees live?
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Q. Is it true that manatees actually have fingernails?
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Q. About how fast do manatees grow, and at what age do they stop?
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Q. I have heard that adult female manatees are larger than adult males. Is this true and, if so, is it known why?
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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?

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. 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?
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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