Subject: Manatee questions! (fwd)

Mike Williamson (pita@www1.wheelock.edu)
Mon, 8 Sep 1997 12:46:10 -0400 (EDT)

---------- Forwarded message ----------
Date: Mon, 8 Sep 1997 11:40:57 +0000
From: manatee@america.com
To: sshirley@dcd.pvt.k12.ma.us
Cc: pita@whale.wheelock.edu
Subject: Many manatee questions!

Dear Ms. Shirley and Dedham Country Day School students,

Thanks for all your great questions about manatees!  Here's the 
answers:

Q. How many bones do manatees have?
A. Manatees have the following bones (starting at the top of the head 
and moving backwards): 
Cranium
6 Cervical Vertebrae
17-19 Thoratic Vertebrae
23-29 Lumbocaudal Vertebrae
7-9 Paired Chevron Bones
Paired Pelvic Bones
17-19 Paired Ribs
Sternum
Flipper Assembly
Hyoid Bones
Mandible

An interesting fact is that manatees and sloths are the only mammals 
that have six cervical (neck) vertebrae.  All other mammals 
(including giraffes!) have seven cervical vertebrae.

Q. Why are manatees so fat?
A.  Although manatees look fat, they actually have very little body 
fat for an aquatic mammal.  Remember, they are a tropical species and 
have no need for body fat to keep them warm.  A large percentage of 
the manatee's body is taken up by the gut tract which contains the 
stomach and intestines etc.  Researchers believe that the manatee's 
large size probably evolved as a result of being aquatic and having a 
herbivorous (plant-eating) diet. The plants manatees eat have a low 
nutritional value, so they make up for that by eating large 
quantities of them.

Q. How long do manatees live?
A. Scientists believe that manatees are capable of living for 60
years or more.  One manatee living in captivity is now over 49 years
old.


Q.  Can you tell us something about the evolution of manatees?
A.  Actual manatee fossils found all over the world go back as far as 
60 million years.  Modern manatees evolved from four-footed land 
mammals. Manatee fossils found in Florida's springs date back about 
45 million years.


Q.  What do manatees eat?
A.  Manatees are herbivores (plant-eaters), feeding on a large 
variety of submerged, emergent, and floating plants.  Seagrass beds 
are important feeding sites for manatees.  Some favorite foods of 
manatees include:

Marine vegetation: Manatee grass, turtle grass, 
shoal grass, widgeon grass. 

Freshwater vegetation: Hydrilla, 
eelgrass, water hyacinth, and water lettuce.


Q.  Where are manatees mostly found?
A.  In the winter, usually November through March, manatees are
concentrated primarily in Florida.  Manatees are susceptible to
cold-related disease, and in the winter, gather near warm water
sources such as natural springs or warm water effluents of power
plants.  Water temperatures below 68 degrees usually cause manatees to
move into these warm water refuge areas.  Individual manatees often
return to the same wintering areas year after year.  In the summer
months, manatees are much more widely distributed and can be found as
far west as Lousiana and as far north as Viginia and the Carolinas.


Q.  Why do manatees live in such shallow waters?
A.  Manatees prefer waters that are 3 to 7 feet deep because this is 
where their food is found. Manatees are found in both salt and fresh 
water.  Along the coast, manatees tend to travel in water that is 
10-16 feet deep, and they are rarely seen in areas over 20 feet deep.

Q.  How many manatees get hit by boats a  day?
A.  Last year, a total of 60 manatees were killed from watercraft 
collisions.  We don't know exactly how many manatees get hit by boats 
every day, but we do know that many adult manatees living in the wild 
bear scars from watercraft collisions.  In fact, manatee scars are so
commonplace, researchers use them as a method of individual
identification.


Q.  How much does the average manatee weigh?
A.  The average adult manatee is about 10-12 feet long and weighs 
about 1,500-1,800 pounds.  However, adult manatees have been 
known to exceed lengths of 13 feet and weigh over 3,500 pounds.  
 
Q.  How big is the world's manatee population?
A.  The last aerial survey of the Florida manatee population was done 
in February of 1997.  The survey showed a population count of 2,229
manatees.  A synoptic survey is a statewide aerial survey designed to
get a head count of individual manatees.  The success of synoptic
surveys is very dependent on weather conditions.  If the weather is
cold and clear, then manatees are gathered around warm water sites,
making it easier to get a "nose" count.  They are not the most
reliable way to determine overall manatee population because so much
depends on weather conditions, but they are the only available method
at present.
     Outside of Florida, little is known about the population of West
Indian manatees or other sirenians in the world. By far, the largest
population of West Indian manatees is found in the U.S. (Florida). 
Elsewhere, they are found in small population pockets throughout their
range.  All sirenian species in the world are considered endangered.


Q.  Are manatees are related to whales? 
A.  Although manatees have similar body shape and overlap in some 
habitat areas, they are not related to dolphins, whales, or sea 
lions.  Surprisingly, the manatee's closest relatives are the 
elephant and the hyrax ( a small, furry animal resembling a rodent.) 

Sincerely,
Nancy Sadusky
Save the Manatee Club