2017-09-01 / Features

I’ve got friends in wet places …

By Escambia County Marine Resources Manager Robert Turpin

A likely origin of the mythical mermaid has been attributed to this month’s Splash! marine life feature: West Indian Manatee (Trichechus matatus). Apparently, some superstitious sailors of centuries past believed in the existence of a half-woman, half-fish. Christopher Columbus also reported mermaid sightings during his early voyages to the Americas.

Sometimes also called “sea cow”-- presumably because of its size, shape and vegetarian diet -- this gentle giant marine mammal may be found in local waters throughout the summer and early autumn.

The Florida Manatee (Trichechus manatus latirostris) is a subspecies of an animal that once ranged throughout the Gulf of Mexico, Western Atlantic Ocean and Caribbean Sea.

Manatee populations significantly declined throughout their original range during the 20th century.

Manatees are protected by state (Florida Manatee Sanctuary Act) and federal (Endangered Species Act and Marine Mammal Protection Act) regulations. These laws prohibit obvious acts such as chasing, disturbing and harassing. It is even against the law to touch manatees.

Robert Turpin Robert Turpin The greatest source of human-caused injury and mortality is vessel strikes. Many manatees bear large scars from encounters with boat propellers. Some researchers use the prop-scars to identify individual manatees.

Many coastal waterways are posted with speed limits for boats to minimize vessel strikes. Some areas have been designated as “Manatee Refuges,” and any entry by humans is prohibitted. These areas are established to allow manatees to rest undisturbed. These areas are particularly important for females with nursing calves. These manatee protection regulations appear to be working, and the Florida manatee population has risen to approximately 6,000.

Manatees are sensitive to cold water temperatures and gather around springs and warm water discharges from power plants in peninsular Florida along the Gulf of Mexico and Atlantic Ocean coasts during the winter. With warming water temperatures in the spring and summer, manatees disperse and migrate up the Florida Gulf of Mexico coast into our local waterways. They are often seen in Santa Rosa Sound, Big Lagoon and in the near-shore Gulf waters as they move westward as far as Texas. Some manatees spend their summers in local waters, feeding on seagrasses and macro-algae. One local species of seagrass (Syringodium filforme) is commonly called “Manatee Grass.” Manatees may consume 5-9 percent of their body weight in vegetation each day.

Some manatees have been fitted with satellite transmitters, allowing researchers to track them throughout their annual migrations. It is during their summer migrations that manatees mate. Female manatees mature at ages 5-7, and males mature at earlier ages (3-5 years). After a 13-month gestation, females usually give birth to a single calf. The calf is provided milk by its mother, and remains with her for one to two years.

Adult manatees achieve a total length of 10-13 feet, weighing 1,000-3,000 pounds. Although only about half of manatees reach ages above 20 years, their maximum lifespan may be 50 years or more.

Manatees are most closely related to elephants. Their only teeth are grinding molars. The front molars are periodically lost and replaced by the ones behind them. Their short, stubby forelimbs have bones remarkably like those of the human hand.

Like all mammals, manatees breathe air. Their long, wide and thin lungs are close to their spines, rather than their ribs, as in other mammals. When resting on the bottom, manatees can remain submerged for 20 minutes. When feeding or swimming at their normal speed of about five miles per hour, manatees surface to breathe about every three to five minutes. Their round, paddle-like tails can propel them at remarkable speeds of 15 miles per hour for short durations.

Their skin is constantly peeling, which may be an adaptation to prevent complete covering by barnacles when manatees inhabit saline waters. They have a translucent nictitating membrane to cover their eyes, but no true eyelids. Instead, their muscles pull the skin around their eyes in a circular pattern.

In late autumn, manatees begin their migration back to their winter habitats. Occasionally, an early cold-snap will cause manatees migrating through our area to seek warmer water in the upper reaches of Pensacola Bay, Escambia Bay, Blackwater Bay or East Bay. If the cold weather is of short duration, the manatees will return to their normal migration routes.

Sometimes, and tragically, manatees succumb to the cold and perish. Cold-stress is one of the leading natural causes of manatee mortality. Harmful algal blooms (also known as “red tides”) are another source of natural mortality.

It is during their winter gatherings that manatees become an important economic resource for some Florida communities. Crystal River, Homosassa Springs, Manatee Springs, Tampa and Fort Myers receive a substantial number of tourists seeking the thrill of snorkeling with manatees.

Manatees are a charismatic species and are true “Florida Natives.” If we can maintain a healthy manatee population, we may also maintain healthy waterways and a healthy

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