The following is an outline of information to be covered for the presentation and topic of “ The vanishing sea cows”. I look forward to meeting you all and for feedback on this topic.
I) What is a manatee?
- It is a marine mammal with no real natural enemies that can live in both salt and fresh water
a) When were they first discovered?
- believed to exist for about 15 million years (ancestors date back to 55 million years ago)
- Columbus and his men in 1493 was the first European to record the sighting
b) Scientific Name
- Family Sirenia
- Florida Species is Trichechus manatus latinostris and is a subspecies of the west Indian manatee (Trichechus manatus) that can be found in Puerto Rico
c) Why were they named this way?
- Manati in Caribbean Indian language means “women’s breast”
d) Why they are sometimes referred to as “mermaids”.
- Sailors thought they looked like them (it is believed that they had been at sea too long, were drunk, insane or something else to believe that.)
- Homer’s “Odyssey” refers to the siren’s song that tried to lure Odysseus and his crew to onto the jagged rocks, was a manatee
a) Evolutionary history
- Scientists used to believe that they were related to the Walrus
- Actually belong to the order of Subungulates that provide for some very unusual offshoots. The order includes: Order Proboscidea (elephant), Hyracoidea (hyraxes that are small furry mammals that resemble rodents) and Tubulidentata (Aardvarks)
- All have the common features of: dental characteristics, lack of a clavicle, and the presence of nails or hooves rather than primitive claws
- Due to their vestigial pelvis, they are believed to have once been land dwelling and then to marine
- Pectoral flippers contain 3-4 vestigial fingernails that look like the elephant’s
b) Bone make-up
- Have only 6 cervical vertebrae as compared to the 7 of most other mammals
- Bones are dense and most lack marrow cavities
c) Life span
- Approximately 50 to 70 years (not really known)
- Mother nuzzles and “talks” to the calf
- Makes squeals, squeaks, chirps, and whistles under the water
- Sound is produced by the larynx
- Most sensitive location for sound is believed to be the area of the cheek bones located behind the eyes
- Also are believed to have adaptations to hear infrasounds (frequencies too low for humans to hear)
- The infrasounds are believed to attract the males when a female is in estrous
- Lack an external ear and the ear opening is very small
- Average 1,000 lbs. however, many are 2,000 lbs. and almost 12 feet in length
- Can get up to 3,500 lbs.
- Lungs are in a separate cavities with separate diaphragms
- They can renew up to 90% of the air in their lungs with a single breath (compared to 10% in humans)
- Have lungs and a diaphragm that allow them to move up and down easily
- Are able to replace their teeth
- Lack front teeth
- Produce Red Blood Cells in the liver, since the bones lack a lot of marrow
- Their eyesight is not good at close range, but can see well up to 100 feet and may be able to detect color.
III) Lifestyle of a manatee
- Warm water as they do not take the cold very well
- Found in water that is at least 1 meter deep and that is connected to a coastal waterway
- Will migrate during warm summer months as far north as Virginia and as far west as Louisiana
- Can be found in the Bahamas on rare occasions
b) Food sources & Diet
- Will eat up to 10% of their body weight (~90 kg)
- Eat up to 6-8 hours a day
- In saltwater mainly eat turtlegrass (Thalassia testudinum), manatee grass (Syringodium filiforme) and shoal grass (Halodule wrightii), they may also eat some algae species, mangrove leaves, and red mangrove seedlings
- In freshwater they mainly eat Hydrilla venticillata, algae, and water hyacinth (Eichhornia crassipes)
- No other competition for food as no other marine animal is an herbivore
- Sometimes they may eat an occasional fish or another manatee’s waste
- Large digestive tract similar to other herbivores
- They have anaerobic bacteria to breakdown cellulose by fermentation
- Food takes seven days to pass through
- Must have access to freshwater periodically to survive
c) How do they live?
- Must rise to the surface to breathe every 4-5 minutes, the longest may be 15-20 minutes
- Newborns will be about 4-ft. long and weigh 60-80 lbs.
- calves nurse by mother’s teats at the base of the flippers
- Usually have a single calf each time (twins are rare)
- Females become sexually mature at 7-8 years
- Males become sexually mature at 9-8 years
- Because of the training involved, they usually only produce calves every 3-5 years
- Gestation period is 13 months
- Males do not help with the raising of the calf
- Polyestrous (more than one cycle a year)
f) Interactions with other manatees
- One animal seldom dominates the other
- They don’t stake out their territory
- The most complex interaction is between the mother and calf
- Calves remain that the mother’s side for 2 years while the mother teaches them to search for food, migratory patterns, etc.
- Body contact is important as they may nuzzle nose to nose or touch flippers
IV) Endangered Species since 1966
- Protected by the Marine mammal act of 1972
- Endangered Species Act of 1975
- Florida manatee sanctuary act of 1978
- A violation to harass, harm, pursue, hunt, shoot, wound, kill, capture, or collect with a maximum fine of $20,000 and/or one year in prison
a) Reasons for being on the list
- 85-90 die each year
- Indians used as a food source that is said to be tender like veal and one manatee could feed an entire village
- Also meat could be stored in its oil and not spoil for a year
- Their oil burns cleaner than putrid whale oil
- Have different amounts of myoglobin in different parts of their body making it taste difference
- Roman Catholics could eat manatees on Friday, as they were considered fish
- Inner ear bones were believed to be a medicine for curing side pains
- Their bones are considered “good luck” charms
- 1800’s museums paid good money for the skeletons and hides
2) Being hit by boats
- Usually lay in the water at the propeller level as they must come to the surface for air
- Fishing is popular in their habitat
- It is hard for them to determine with the way their hearing works, as to where the boats are located
3) Habitat being changed by coastal development
- Power plants produce warm water that they are drawn to and then there is no food source for them or a cold weather spell in the area could kill them
- 80% of the seagrass beds have been destroyed from runoffs of oil, pesticide, and toxic substances
4) Red Tide
5) Global changes in the weather
- Cold weather is a threat to them as they do not have a thick layer of fat
- Prolonged exposure to less than 60 degrees they often die
- Teeth are only made for eating and they have no claws so their only defense is to swim away
- Reproduction is a slow rate
- The metabolic rate is slow for a marine animal
b) What can be done to save them from extinction?
- Restore their feeding areas
- They are hard to hand raise as they need the mother’s teaching to survive
c) Protected areas (see population)
- Blue Springs State Park
- Crystal River on the Gulf Coast
V) Study of the population
- Florida has the only resident population in the U.S.
- West Indian manatee is found in Puerto Rico, parts of South America and Mexico
- Also the Amazonian species lives in the fresh water of the Amazon and Orinoco River
- West African manatee lives on the west coast of Africa
- Dugong is scattered thoughout Indo-pacific and northern Australia (these once lived in Florida and was displaced by the manatee)
b) Numbers believed to exist
- Hard to tell, but scientists believe there is a minimum of 1200 in Florida
c) Tracking them
- Radiotrasmitters are attached to their tail with a belt that will break if caught, thus allowing scientists to track them.
d) In Florida
- Crystal River (80 miles N of Tampa) from December to mid February is a place where they winter and snorkelers can swim with them
- Blue Springs State Park (in Deland , N or Orlando) winter from mid-November to mid-March
- Miami Seaquarium helps with recovery and rehabilitation
- Sea World in Orland also has rescue and rehab
- Epcot Center
- Lowry Park Zoo in Tampa (funded by Pepsi) and also has a critical care facility
- South Florida museum and Bishop planetarium has Snooty the first manatee born in captivity
- Homosassa Springs is a half-way house for injured manatees to be later released back into the wild
- Many artificial warm-water areas around power plants
Darling, Kathy. Manatee on Location. Lothrop, Lee and Shepard Books. 1991
Dietz, Tim. The Call of the Siren. Fulcrum Publishing. 1992.
Hartman, Daniel. Ecology and Behavior of the Manatee (Tricheschus manatus) in Florida. Special publication #5 The American Soceity of the Mammologists. 1979.
O’Keefe, Timothy M. Manatees Our Vanishing Mermaids. Larsen’s outdoor publishing. 1993.
O’Shea, Thomas; Ackerman, Bruce; & Percival, Franklin H. Population Biology of the Florida Manatee. U. S. Department of the Interior: National Biological Service. August 1995.
Reynolds, John E. and Daniel Odell. Manatees and Dugongs. Facts on File. 1991.
Silverstein, Robert, Virginia, & Alvin; Nunn, Laura Silverstein. The Manatee. The Millbrook Press. 1995.
Zeiller, Warren. Introducing the Manatee University Press of Florida. 1992.
Online Zooligists: Sirends www.rtis.com/nat/user/elberry/marspec/pms_siren_spc.html
The wonderful world of the Manatee www.manateeworld.net/
Manatees: A Seaworld Education Department Resource www.seaworld.org/manatee/manatees.html
Manatee: The call of the Siren www.aol.com/carynbol/index.html/homepage.html
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