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Dive Dry with Dr. Bill

#415: Mermaid or Wo-Manatee?

There is a legend of sorts associated with sailors who entered subtropical and tropical waters after long voyages of discovery or trade. They would claim to have encountered beautiful females, some said mermaids, in the waters they sailed. Later, historians and scientists would suggest that these early explorers and men of commerce were actually seeing manatees rather than mermaids. Now, I always attributed their error in judgment to the long voyages with little other than rum to drink... or perhaps the fact that few vessels sailed with an on-board optometrist. I also questioned why these mammals would be referred to as "man"atees when they were mistaken for women. Why not wo-manatees?

During my stay with Mom in sunny Florida, I spent a fair bit of time observing and filming the five manatees in the boat harbor below her condo. I wore my glasses, and my lips have not touched unadulterated rum since the night I got violently ill on it freshman year in college. Anyone who would mistake these marine mammals for a lovely woman was truly deranged... or extremely desperate! It reassured me that I was not either of these. They didn't receive their other common name, sea cow, in a beauty contest.

There are only three living species of manatee in the world. All are in the genus Trichechus and order Sirenia along with the dugongs. They include the Amazonian manatee, the West African manatee and the West Indian manatee which I observed. It is interesting to note that they are distant relatives of the elephant. The name "manati" comes from the Taino, a people residing in the Caribbean prior to the arrival of Columbus in the New World. The word means "breast."

The manatee is Florida's state marine mammal. They are largely herbivorous, feeding on plant life in both fresh and salt water using their lips to tear it from the bottom. In captivity they are often fed heads of lettuce. A manatee may consume as much as 10% of its body weight per day. Cellulose from their plant food is digested using bacteria in the hind gut. To ensure they extract the greatest amount of nutrition from their diet, the intestines may be as long as 150 feet. The plant food is somewhat abrasive, causing their grinding molars to have to be replaced frequently.

Despite this rather selective diet, an individual manatee may weigh up to 1,800 pounds and reach 10-12 feet in length. Their lifespan is believed to be 50-60 years in the wild. Their coloration is gray. They have flattened flippers and a broad, rounded tail used for propulsion at speeds up to 20 mph although the normal cruising speed is only two to six. The population in Florida is believed to be about 3,000.

During winter, these manatees reside in the warmer, coastal waters including bays and estuaries as well as shallow rivers. They prefer temperatures above 68 F (20 C), and will move further south during cold spells. These gentle creatures are usually very slow moving, spending much of their time feeding or resting. Boaters in Mom's condo development told me the manatees often surfaced to be scratched by humans, and a diver who cleaned boat hulls in the dark, murky waters there said they would occasionally bump into him and rub their bodies against him. He didn't mistake them for women... but he did think they might be alligators

There were two young manatees in the group of five I observed. Apparently there is no specific mating season. The poor female may be pursued for weeks by potential suitors, and they compete for her affection. Mating takes place in the water and may be accomplished using a number of different positions (none of which can be found in the Kama Sutra). Generally only a single calf three to four feet long and weighing 60-70 pounds is born after a 12-13 month gestation period. Twins are occasionally delivered. The cows nurse their young underwater, so I guess they must be somewhat modest. Sea cows communicate with one another underwater using chirps and squeals when excited, stressed or sexually aroused. Mothers also communicate with their young using sound. The ones I observed were silent at the surface except when one would sharply exhale through its nostrils before taking another breath.

When not actively feeding near the bottom, the manatees often "logged" or rested at the surface with only a part of their body exposed. This activity makes them difficult for boaters to see them, and they are occasionally struck and killed when mortal wounds are inflicted by a boat's propeller or hull. Non-lethal wounds that have healed are almost always evident on their bodies. Another threat comes from toxic algal blooms including red tides which killed as many as 150 manatees in 1996. These are linked to global warming in the Gulf of Mexico. Development and other alteration of their coastal and river habitat also impacts the health of these populations. The manatee is recognized as endangered under the federal Endangered Species Act, and they are also protected by the 1972 Marine Mammal Protection Act.

© 2010 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Cow and calf "logging" near the surface and taking a breath before submerging; the manatee's paddle
shaped tail and the head of one as seen in an aquarium at Mote Marine Lab

This document maintained by Dr. Bill Bushing.
Material and images © 2010 Star Thrower Educational Multimedia