Subject: Manatees

Martine Berube (mberube@ulb.ac.be)
Tue, 12 May 1998 15:26:50 +0200 (MET DST)

Dear Teresa McClure,
I am not an expert in manatees but I have found this site which can help you
and your students a lot (http://www.objectlinks.com/manatee/faq.htm). 

1-We want to know how a manatee hears if it does not have any outside ears? 
AND
2-Do manatees seem to have a kind of communication like whales do? 

Answer:
"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 indirect contact with the ear bones. This
arrangement is similar to that of dolphins. 

In addition, anatomical studies suggest that manatees are adapted to hear
infrasound, frequencies too low to be heard by the human
ear, generally less than 20 hertz." 

3-Also, where are the ears located? 

Answer: They are located several centimeters behind the eyes.

4-We were also wondering if manatees live anywhere besides Florida?  

Answer: Yes, they live in other part of the world. Please look at this
website, there is a very good map showing where in the world you can see
manatees (http://www.objectlinks.com/manatee/sirenian.htm).

5-How long do manatees live?  

Answer: Scientists believe that manatees are capable of living for 60 years
or more. One manatee living in captivity is now over 48 years
old. 

6-What are some other enemies manatees have besides motorboats and humans? 

Answer: The only other ennemy to the manatees would be the loss of their
habitat which is very serious today.

7-In our story, Sam likes to eat water hyacinths - what other kinds of
plants do 
they like? 

Answer: Some favorite foods of manatees in Florida include: manatee grass, 
turtle grass, shoal grass, widgeon grass, hydrilla, tapegrass, water 
hyacinth, and water lettuce.

8-Are there different kinds of manatees? 

Answer: The manatees are members of the order Sirenia, a group of aquatic
mammals popularly known as the sea cows. Only four living species in two
genera currently exist: three manatees and one dugong. These include the
Amazon Manatee, the West Indian Manatee, the West African Manatee, and the
dugong. Another Dugongid, the Stellers sea cow, was exterminated by North
Pacific sealers in the 18th century.


9-Can manatees jump out of the water?

Answer: I don't think so. But to tell you the truth I don't know if anyone
as seen one jumping out of the water.   

>
>Obviously, I have a VERY curious class! :-)  The children generated all 
>these questions - I think some of them are pretty good.  Thanks for 
>taking the time to answer our questions about manatees.
>
>Teresa McClure
>2nd grade teacher
>Chimneyrock Elementary
>Cordova, TN  (a suburb of Memphis)
>
>
Martine Berube
Unit of Evolutionary Genetics
Department of Molecular Biology
Free University of Brussels (ULB)
CP 244
Bld du Triomphe
B-1050 Brussels, Belgium
Tel: +32 2 650 5427
Fax: +32 2 650 5421
Email: mberube@ulb.ac.be