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The West Indian Manatee
In warmer months manatees spend most of
their time at sea and out of harm's way, but from October
31st to March 31st, the colder weather drives them inland
to places where can find warm water. Florida's Crystal
River National Wildlife Refuge supports the largest
concentration. During the summer months the best time to
catch them is in the morning when they are frolicking and
sunning. They usually stay in one area when they are in
the "morning mode" and can be approached quite
easily. In the afternoon, when the sun is hot they stay
mainly on the bottom or are on the move for food. When
the air temperature drops below the water temperature of
72 degrees (72 degrees is the year round temperature for
Crystal River) for several days, hundreds upon hundreds
of manatee are in river. Best sightings are on the
coldest days of the year. The West Indian manatee (Trichechus manatus
latirostris) is a large, gray-brown, aquatic mammal with
a body that tapers to a flat, paddle-shaped tail. It has
two flippers with 3 to 4 nails on each, and it's head and
face are wrinkled, with whiskers on the snout. The
manatee's closest relatives are the elephant, hyraxes,
and aardvarks than any other marine mammal. Manatees are
believed to have evolved from a wading plant-eating
animal. The West Indian manatee is related to the West
African manatee, the Amazonian manatee, the dugong and
the Steller's sea cow, which was hunted to extinction in
1768, just 27 years after it was discovered in 1741. The
average, adult manatee is about 10 feet long and weighs
about 1000 pounds. They can reach up to 13 feet in length
and weigh up to 3,000 pounds. Manatees belong to the order Sirenia. The
word "Sirenia" came from the word "siren."
"Sirens" are legendary Greek sea beauties that
lured sailors in to the sea. It is thought that old-time
mermaid sightings were actually sirenians rather than
mythical half women, half fish. Manatees are a migrant species, concentrated
in Florida in the winter, but can be found as far west as
Louisiana and as far north as Virginia and the Carolinas
in the summer months. The Manatee lives in warm, shallow
rivers, bays, estuaries and coastal waters. Because
manatee have an unusually low metabolic rate, they
usually don't live in waters that are below 68 degrees
Fahrenheit. They often live in the warm run off water of
power plants. They prefer shallow waters (3 to 6 feet
deep) that produce the salt and fresh water plants that
they eat. During the winter months as many as 500
manatees can be found in the Crystal River area. During
the summer as few as 50 remain in the river. The West
Indian manatee can also be found in the coastal and
inland waterways of Central America and along the
northern coast of South America, although distribution in
these areas may be spotty. Manatees are gentle, slow-moving graceful
swimmers. Most of their time is spent eating, resting and
in travel. Manatees are completely herbivorous. They eat
aquatic plants and can consume 10-15% of their body
weight daily. Upon occassion they will consume shell fish.
They graze for food along water bottoms and on the
surface. They may rest submerged at the bottom or just
below the surface, coming up to breathe on the average of
every three to five minutes and twenty minutes and longer
when asleep. Manatee bones are very dense, lacking marrow.
Because of this, manatees are negatively buoyant and can
lie on the sea bottom without exerting any energy to stay
down. The less energy they use, the longer manatees can
remain submerged between breaths making feeding more
efficient. Manatees have the ability to control the
volume of air their lungs, enabling them to rise to the
surface, take a breath, and return to the bottom with no
noticeable effort. Manatees have no natural enemies, and it is
believed they can live 60 years or more. Most human
related manatee mortalities occur from collisions with
watercraft. Other causes of human related mortalities
include being crushed and/or drowned in canal locks and
flood control structures; ingestion of fish hooks, litter
and monofilament line; entanglement in crab trap lines;
and vandalism. Ultimately, however, loss of habitat is
the most serious threat facing the manatee today. There
are approximately 3000 West Indian manatees left in the
United States. In 2001 Florida recorded 325 manatee
deaths. In 2002, 305 have perished. Scientists from the
Florida Fish and Wildlife Conservation Commission’s
Florida Marine Research Institute suspect that 27 manatee
carcasses brought in from four southwest counties between
March 15 and April 16 2002 died as a result of exposure
to red tide. The 2003 count, counted only 2, 568 manatess,
down 17.5% from last year, a loss of 545 manatees. The Florida Fish and Wildlife Conservation
Commission and the Florida Marine Research Institute have
submitted a report envolving a complex scientific process
that included compiling the best available data on the
manatee and developing a population viability analysis
model to project the probability of a population decline
and extinction in the next 45 and 100 years. Among the
data incorporated into the model were survival rates, age
of maturity, age of first reproduction, and potential
catastrophic events such as red tide and cold weather.
Eighteen FMRI and other FWC staff contributed to the 151-page
report. It represents the most comprehensive analysis of
manatee population data to date. The manatee is protected under federal law
by the Marine Mammal Protection Act of 1972 and the
Endangered Specials Act of 1973, which make it illegal to
harass, hunt, capture or kill any marine mammal. The
manatee is also protected by the Florida Manatee
Sanctuary Act of 1978, which states: "It is unlawful
for any person, at any time, intentionally or negligently,
to annoy, molest, harass or disturb any manatee."
Anyone convicted of violating Florida's
state law faces a possible maximum fine of $1,000 and/or
imprisonment for up to 60 days. Conviction on the federal
level is punishable by a fine of up to $100,000 and/or
one year in prison. Additional
information on the Manatee: http://www.floridamarine.org/ |
