Manatee – Part 3

Ecology

Range and habitat

Manatees inhabit the shallow, marshy coastal areas and rivers of the Caribbean Sea and the Gulf of Mexico (T. manatus, West Indian manatee), the Amazon basin (T. inunguis, Amazonian manatee), and West Africa (T. senegalensis, West African manatee).[

West Indian manatees prefer warmer temperatures and are known to congregate in shallow waters. They frequently migrate through brackish water estuaries to freshwater springs. They cannot survive below 15 °C (60 °F). Their natural source for warmth during winter is warm, spring-fed rivers.

Underwater photo of three manatees swimming along bottom

A group of three manatees

West Indian

The coast of the state of Georgia is usually the northernmost range of the West Indian manatees because their low metabolic rate does not protect them in cold water. Prolonged exposure to water below 20 °C (68 °F) can cause “cold stress syndrome” and death.[

Florida manatees can move freely between fresh water and salt water.

Manatees have been seen as far north as Cape Cod, and in 1995 and again in 2006, one was seen in New York City and Rhode Island’s Narragansett Bay. A manatee was spotted in the Wolf River harbor near the Mississippi River in downtown Memphis in 2006, and was later found dead 10 miles downriver in McKellar Lake.

The West Indian manatee migrates into Florida rivers—such as the Crystal, the Homosassa, and the Chassahowitzka rivers, whose head springs are 22 °C (72 °F) all year. In November to March, about 400 West Indian manatees (according to the National Wildlife Refuge) gather in the rivers in Citrus County, Florida.

In winter, manatees often gather near the warm-water outflows of power plants along the Florida coast, instead of migrating south as they once did. Some conservationists are concerned that these manatees have become too reliant on these artificially warmed areas.[ The U.S. Fish and Wildlife Service is trying to find a new way to heat the water for manatees that depended on plants that have closed. The main water treatment plant in Guyana has four manatees that keep storage canals clear of weeds; there are also some in the ponds of the national park in Georgetown, Guyana.

Studies suggest that Florida manatees need access to fresh water for proper regulation of water and salts in their bodies.

Accurate population estimates of the Florida manatee (T. manatus) are difficult. They have been called scientifically weak because they vary widely from year to year, some areas showing increases, others decreases, and little strong evidence of increases except in two areas. Manatee counts are highly variable without an accurate way to estimate numbers: In Florida in 1996, a winter survey found 2,639 manatees; in 1997, a January survey found 2,229, and a February survey found 1,706. A statewide synoptic survey in January 2010 found 5,067 manatees living in Florida, the highest number recorded to that time.[

As of January 2016, the USFWS estimates the range-wide manatee population to be at least 13,000; as of January, 2018, at least 6,100 are estimated to be in Florida.[

Population viability studies conducted in 1997 found that decreasing adult survival and eventual extinction were a probable future outcome for Florida manatees unless they got more protection. The U.S. Fish and Wildlife Service proposed downgrading the manatee’s status from endangered to threatened in January 2016 after more than 40 years of the manatee’s being classified as on the endangered.[

Fossil remains of Florida manatee ancestors date back about 45 million years.[c

Amazonian

The freshwater Amazonian manatee (T. inunguis) inhabits the Amazon River and its tributaries, and never ventures into salt water.[

West African

They are found in coastal marine and estuarine habitats, and in freshwater river systems along the west coast of Africa from the Senegal River south to the Cuanza River in Angola. They live as far upriver on the Niger River as Koulikoro in Mali, 2,000 km from the coast.

Conservation

All three species of manatee are listed by the World Conservation Union as vulnerable to extinction.

It is illegal under federal and Florida law to injure or harm a manatee. They are classified as “endangered” by both the state and the federal governments.

The MV Freedom Star and MV Liberty Star, ships used by NASA to tow space shuttle solid rocket boosters back to Kennedy Space Center, are propelled only by water jets to protect the endangered manatee population that inhabits regions of the Banana River where the ships are based.

Brazil outlawed hunting in 1973 in an effort to preserve the species. Deaths by boat strikes are still common.

In January 2016, the U.S. Fish and Wildlife Service proposed that the West Indian manatee be reclassified from an “endangered” status to “threatened” as improvements to habitat conditions, population growth and reductions of threats have all increased. The proposal will not affect current federal protections.[

As of February 2016, 6,250 manatees were reported swimming in Florida’s springs.[

Hunting

Underwater profile photo of light-colored animal with small flippers

T

Manatees were traditionally hunted by indigenous Caribbean people. When Christopher Columbus arrived in the region, hunting was already an established trade, although this is less common today.[

The primary hunting method was for the hunter to approach in a dugout canoe, offering bait to attract it close enough to temporarily stun it with a blow near the head from an oar-like pole. Many times the creature would flip over, leaving it vulnerable to further attacks.

From manatee hides, Native Americans made war shields, canoes, and shoes, though manatees were predominantly hunted for their abundant meat.

Later, manatees were hunted for their bones, which were used to make “special potions”. Until the 1800s, museums paid as much as $100 for bones or hides. Though hunting was banned in 1893, poaching continues today.

More about Mantees in Part 4 of this series!

(Information obtained from Wikipedia.com)