West Indian Manatee
Encyclopedia
The West Indian Manatee (Trichechus manatus) is a manatee
, and the largest surviving member of the aquatic mammal
order Sirenia
(which also includes the Dugong
and the extinct Steller's Sea Cow
). The West Indian Manatee, Trichechus manatus, is a species distinct from the Amazonian Manatee, T. inunguis
, and the West African Manatee, T. senegalensis. Based on genetic and morphological studies, the West Indian Manatee is divided into two sub-species, the Florida Manatee (T. m. latirostris) and the Antillean Manatee or Caribbean Manatee (T. m. manatus). However, recent genetic (mtDNA) research suggests that the West Indian manatee actually falls out into three groups, which are more or less geographically distributed as: (1) Florida and the Greater Antilles; (2) Central and Northern South America; and (3) Northeastern South America.
on their thick skin. The average West Indian Manatee is approximately 2.7–3.5 m (8.9–11.5 ft) long and weighs 200–600 kg (440.9–1,322.8 lb), with females generally larger than males. The largest individuals can weigh up to 1500 kg (3,306.9 lb) and measure up to 4.6 m (15.1 ft). The Manatee's color is gray or brown. Their flippers also have either 3 or 4 nails so they can hold their food as they are eating.
, generally in shallow coastal areas. However, it is known to withstand large changes in water salinity
, and so has also been found in shallow river
s and estuaries
. They can live in fresh water, saline water, and even brackish water. It is limited to the tropics and subtropics due to an extremely low metabolic rate and lack of a thick layer of insulating body fat
. In the winter, West Indian Manatees can be found in Florida. During summer, these large mammals have even been found as far north as New York City
, New York
and as far west as Texas.
The Florida manatee (Trichechus manatus latirostris), a subspecies of the West Indian manatee, is the largest of all living sirenians. Florida manatees inhabit the most northern limit of sirenian habitat. Over three decades of research by universities, governmental agencies, and NGOs, have contributed to our understanding of Florida manatee ecology and behavior, which is more than we know about any other sirenian species. They are found in fresh water rivers, in estuaries, and in the coastal waters of the Gulf of Mexico
and the Atlantic Ocean
. Females usually have their first calf when they are about 7 or 8 years old. Normally they only have one calf every three years because manatees nurse their calf for 1 or 2 years, but there are rare occurrences of twins. When a calf is born, they usually weigh between 60 and 70 pounds and are between 4 and 4.5 feet. The family unit consists of mother and calf, which remain together for up to 2 years. Males aggregate in mating herds around a female when she is ready to conceive, but contribute no parental care to the calf. Florida manatees may live to be greater than 60 years old in the wild. In captivity, West Indian Manatees live up to 28 years. The biggest single threat to Florida manatees is death from collisions with recreational watercraft. Large concentrations of Florida manatees are located in the Crystal River area and also Wakulla Springs regions in central and north Florida. The best time to see the Wakulla Springs manatees are in November and December, and in the spring for the Crystal River manatees.
The other subspecies of the West Indian manatee is sometimes referred to as the Antillean manatee (Trichechus manatus manatus). Antillean manatees are sparsely distributed throughout the Caribbean and the Northwestern Atlantic Ocean, from Mexico
, east to the Greater Antilles
, and south to Brazil
. They are found in French Guiana
, Suriname
, Guyana
, Trinidad
(however there has been a lack of recent sightings), Venezuela
, Colombia
, Panama
, Costa Rica
, Nicaragua
, Honduras
, Guatemala
, Belize
, Mexico, Cuba
, Haiti
, Dominican Republic
, Jamaica
, and Puerto Rico
. Historically, Antillean manatees were hunted by local natives and sold to European explorers for food. Today, they are threatened by loss of habitat, poaching, entanglement with fishing gear, and increased boating activity. Several of Sirenian International's scientists study Antillean manatees in Belize, which may be the last stronghold for the subspecies. Funds for research, education, and conservation projects are desperately needed in other Central American nations.
The West Indian Manatee is surprisingly agile in water, and individuals have been seen doing rolls, somersaults, and even swimming upside-down. Manatees are not territorial and do not have complex predator avoidance behavior, as they have evolved in areas without natural predators.
The West Indian Manatee is an opportunistic feeder, with large adults consume 10% to 15% of the body weight in food daily. Manatees feed on about 60 plant species which includes sea grasses as their major food source. They also consume some fish and small invertebrates. Because manatees feed on abrasive plants, their molars are often worn down and are continually replaced throughout life.
The West Indian Manatee has a high casualty rate due to thermal shock from cold temperatures. During cold weather many die due to their digestive tract shutting down at water temperatures below 68 degrees fahrenheit. Many manatee deaths are caused by large commercial vessels but are attributed to "recreational watercraft" due to the elimination of that classification.
Due to their low reproductive rates, a decline in manatee population may be hard to overcome. They enjoy protection from the U.S. Endangered Species Act
of 1973, and the U.S. Marine Mammal Protection Act
of 1972. The West Indian Manatee is also protected by the Florida Manatee Sanctuary Act of 1978, the Manatee Recovery Plan, and the Save the Manatee Club. However, in April 2007, the U.S. Fish and Wildlife Service announced that the West Indian manatee population of Florida had rebounded. It advised that the species be reclassified as "threatened" rather than "endangered". A computer model produced for the federal study showed a 50 percent chance that the current statewide manatee population of about 3,300 could dwindle over the next 50 years to just 500 on either coast.
The Florida manatee subspecies (Trichechus manatus latirostris) was listed in October 2007 as Endangered by the IUCN on the basis of a population size of less than 2,500 mature individuals and a population that is estimated to be in decline by at least 20% over the next two generations (estimated at ~40 years) due to anticipated future changes in warm-water habitat and threats from increasing watercraft traffic over the next several decades.
During the winter months, manatees often congregate near the warm water outflows of power plants along the coast of Florida instead of migrating south as they once did, causing some conservations to worry that they 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 are dependent on plants that have closed.
Manatee
Manatees are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows...
, and the largest surviving member of the aquatic mammal
Aquatic mammal
Aquatic and semi-aquatic mammals are a diverse group of mammals that dwell partly or entirely in bodies of water. They include the various marine mammals who dwell in oceans, as well as various freshwater species, such as the Platypus and the European Otter.-Groups:* Order Sirenia: Sirenians**...
order Sirenia
Sirenia
Sirenia is an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. Four species are living, in two families and genera. These are the dugong and manatees...
(which also includes the Dugong
Dugong
The dugong is a large marine mammal which, together with the manatees, is one of four living species of the order Sirenia. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's sea cow , was hunted to extinction in the 18th century...
and the extinct Steller's Sea Cow
Steller's Sea Cow
Steller's sea cow was a large herbivorous marine mammal. In historical times, it was the largest member of the order Sirenia, which includes its closest living relative, the dugong , and the manatees...
). The West Indian Manatee, Trichechus manatus, is a species distinct from the Amazonian Manatee, T. inunguis
Amazonian Manatee
The Amazonian Manatee is a species of manatee that lives in the freshwater habitats of the Amazon basin. They are found in Brazil, Peru, Colombia, Ecuador, Guyana and Venezuela. Amazonian manatees are aquatic animals of the Sirenia order and are also known as "seacows". Their colour is grey but...
, and the West African Manatee, T. senegalensis. Based on genetic and morphological studies, the West Indian Manatee is divided into two sub-species, the Florida Manatee (T. m. latirostris) and the Antillean Manatee or Caribbean Manatee (T. m. manatus). However, recent genetic (mtDNA) research suggests that the West Indian manatee actually falls out into three groups, which are more or less geographically distributed as: (1) Florida and the Greater Antilles; (2) Central and Northern South America; and (3) Northeastern South America.
Physical description
Like other manatees, the West Indian Manatee has adapted fully to an aquatic life style, having no hind limbs. Pelage cover is sparsely distributed across the body, which may play a role in reducing the build-up of algaeAlgae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
on their thick skin. The average West Indian Manatee is approximately 2.7–3.5 m (8.9–11.5 ft) long and weighs 200–600 kg (440.9–1,322.8 lb), with females generally larger than males. The largest individuals can weigh up to 1500 kg (3,306.9 lb) and measure up to 4.6 m (15.1 ft). The Manatee's color is gray or brown. Their flippers also have either 3 or 4 nails so they can hold their food as they are eating.
Habitat and geographic range
As its name implies, the West Indian manatee lives in the West Indies, or CaribbeanCaribbean
The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...
, generally in shallow coastal areas. However, it is known to withstand large changes in water salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
, and so has also been found in shallow river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s and estuaries
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
. They can live in fresh water, saline water, and even brackish water. It is limited to the tropics and subtropics due to an extremely low metabolic rate and lack of a thick layer of insulating body fat
Blubber
Blubber is a thick layer of vascularized adipose tissue found under the skin of all cetaceans, pinnipeds and sirenians.-Description:Lipid-rich, collagen fiber–laced blubber comprises the hypodermis and covers the whole body, except for parts of the appendages, strongly attached to the musculature...
. In the winter, West Indian Manatees can be found in Florida. During summer, these large mammals have even been found as far north as New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
, New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
and as far west as Texas.
The Florida manatee (Trichechus manatus latirostris), a subspecies of the West Indian manatee, is the largest of all living sirenians. Florida manatees inhabit the most northern limit of sirenian habitat. Over three decades of research by universities, governmental agencies, and NGOs, have contributed to our understanding of Florida manatee ecology and behavior, which is more than we know about any other sirenian species. They are found in fresh water rivers, in estuaries, and in the coastal waters of the Gulf of Mexico
Gulf of Mexico
The Gulf of Mexico is a partially landlocked ocean basin largely surrounded by the North American continent and the island of Cuba. It is bounded on the northeast, north and northwest by the Gulf Coast of the United States, on the southwest and south by Mexico, and on the southeast by Cuba. In...
and the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. Females usually have their first calf when they are about 7 or 8 years old. Normally they only have one calf every three years because manatees nurse their calf for 1 or 2 years, but there are rare occurrences of twins. When a calf is born, they usually weigh between 60 and 70 pounds and are between 4 and 4.5 feet. The family unit consists of mother and calf, which remain together for up to 2 years. Males aggregate in mating herds around a female when she is ready to conceive, but contribute no parental care to the calf. Florida manatees may live to be greater than 60 years old in the wild. In captivity, West Indian Manatees live up to 28 years. The biggest single threat to Florida manatees is death from collisions with recreational watercraft. Large concentrations of Florida manatees are located in the Crystal River area and also Wakulla Springs regions in central and north Florida. The best time to see the Wakulla Springs manatees are in November and December, and in the spring for the Crystal River manatees.
The other subspecies of the West Indian manatee is sometimes referred to as the Antillean manatee (Trichechus manatus manatus). Antillean manatees are sparsely distributed throughout the Caribbean and the Northwestern Atlantic Ocean, from Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, east to the Greater Antilles
Greater Antilles
The Greater Antilles are one of three island groups in the Caribbean. Comprising Cuba, Jamaica, Hispaniola , and Puerto Rico, the Greater Antilles constitute almost 90% of the land mass of the entire West Indies.-Greater Antilles in context :The islands of the Caribbean Sea, collectively known as...
, and south to Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. They are found in French Guiana
French Guiana
French Guiana is an overseas region of France, consisting of a single overseas department located on the northern Atlantic coast of South America. It has borders with two nations, Brazil to the east and south, and Suriname to the west...
, Suriname
Suriname
Suriname , officially the Republic of Suriname , is a country in northern South America. It borders French Guiana to the east, Guyana to the west, Brazil to the south, and on the north by the Atlantic Ocean. Suriname was a former colony of the British and of the Dutch, and was previously known as...
, Guyana
Guyana
Guyana , officially the Co-operative Republic of Guyana, previously the colony of British Guiana, is a sovereign state on the northern coast of South America that is culturally part of the Anglophone Caribbean. Guyana was a former colony of the Dutch and of the British...
, Trinidad
Trinidad
Trinidad is the larger and more populous of the two major islands and numerous landforms which make up the island nation of Trinidad and Tobago. It is the southernmost island in the Caribbean and lies just off the northeastern coast of Venezuela. With an area of it is also the fifth largest in...
(however there has been a lack of recent sightings), Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
, Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
, Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...
, Costa Rica
Costa Rica
Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....
, Nicaragua
Nicaragua
Nicaragua is the largest country in the Central American American isthmus, bordered by Honduras to the north and Costa Rica to the south. The country is situated between 11 and 14 degrees north of the Equator in the Northern Hemisphere, which places it entirely within the tropics. The Pacific Ocean...
, Honduras
Honduras
Honduras is a republic in Central America. It was previously known as Spanish Honduras to differentiate it from British Honduras, which became the modern-day state of Belize...
, Guatemala
Guatemala
Guatemala is a country in Central America bordered by Mexico to the north and west, the Pacific Ocean to the southwest, Belize to the northeast, the Caribbean to the east, and Honduras and El Salvador to the southeast...
, Belize
Belize
Belize is a constitutional monarchy and the northernmost country in Central America. Belize has a diverse society, comprising many cultures and languages. Even though Kriol and Spanish are spoken among the population, Belize is the only country in Central America where English is the official...
, Mexico, Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
, Haiti
Haiti
Haiti , officially the Republic of Haiti , is a Caribbean country. It occupies the western, smaller portion of the island of Hispaniola, in the Greater Antillean archipelago, which it shares with the Dominican Republic. Ayiti was the indigenous Taíno or Amerindian name for the island...
, Dominican Republic
Dominican Republic
The Dominican Republic is a nation on the island of La Hispaniola, part of the Greater Antilles archipelago in the Caribbean region. The western third of the island is occupied by the nation of Haiti, making Hispaniola one of two Caribbean islands that are shared by two countries...
, Jamaica
Jamaica
Jamaica is an island nation of the Greater Antilles, in length, up to in width and 10,990 square kilometres in area. It is situated in the Caribbean Sea, about south of Cuba, and west of Hispaniola, the island harbouring the nation-states Haiti and the Dominican Republic...
, and Puerto Rico
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
. Historically, Antillean manatees were hunted by local natives and sold to European explorers for food. Today, they are threatened by loss of habitat, poaching, entanglement with fishing gear, and increased boating activity. Several of Sirenian International's scientists study Antillean manatees in Belize, which may be the last stronghold for the subspecies. Funds for research, education, and conservation projects are desperately needed in other Central American nations.
Behavior and food
The West Indian Manatee is an opportunistic feeder, with large adults consume 10% to 15% of the body weight in food daily. Manatees feed on about 60 plant species which includes sea grasses as their major food source. They also consume some fish and small invertebrates. Because manatees feed on abrasive plants, their molars are often worn down and are continually replaced throughout life.
The West Indian Manatee has a high casualty rate due to thermal shock from cold temperatures. During cold weather many die due to their digestive tract shutting down at water temperatures below 68 degrees fahrenheit. Many manatee deaths are caused by large commercial vessels but are attributed to "recreational watercraft" due to the elimination of that classification.
Reproduction
Although female West Indian manatees are mostly solitary creatures, they form mating herds while in estrus. Most females breed successfully between ages of seven and nine; they are, however, capable of reproduction as early as four years of age. The gestation period (pregnancy) lasts from twelve to fourteen months. Normally, one calf is born, although on rare occasions two have been recorded. The young are born with molars, allowing them to consume sea grass within the first three weeks of birth. On average, manatees that survive to adulthood will have between five and seven offspring between the ages of 20 and 26.Manatee interaction with humans
The West Indian Manatee has been hunted for hundreds of years for meat and hide, and continues to be hunted to this day in Central and South America. Illegal poaching, as well as collisions with speeding motorboats, are a constant source of manatee fatalities.Due to their low reproductive rates, a decline in manatee population may be hard to overcome. They enjoy protection from the U.S. Endangered Species Act
Endangered Species Act
The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...
of 1973, and the U.S. Marine Mammal Protection Act
Marine Mammal Protection Act
The Marine Mammal Protection Act of 1972 was the first article of legislation to call specifically for an ecosystem approach to natural resource management and conservation. MMPA prohibits the taking of marine mammals, and enacts a moratorium on the import, export, and sale of any marine mammal,...
of 1972. The West Indian Manatee is also protected by the Florida Manatee Sanctuary Act of 1978, the Manatee Recovery Plan, and the Save the Manatee Club. However, in April 2007, the U.S. Fish and Wildlife Service announced that the West Indian manatee population of Florida had rebounded. It advised that the species be reclassified as "threatened" rather than "endangered". A computer model produced for the federal study showed a 50 percent chance that the current statewide manatee population of about 3,300 could dwindle over the next 50 years to just 500 on either coast.
The Florida manatee subspecies (Trichechus manatus latirostris) was listed in October 2007 as Endangered by the IUCN on the basis of a population size of less than 2,500 mature individuals and a population that is estimated to be in decline by at least 20% over the next two generations (estimated at ~40 years) due to anticipated future changes in warm-water habitat and threats from increasing watercraft traffic over the next several decades.
During the winter months, manatees often congregate near the warm water outflows of power plants along the coast of Florida instead of migrating south as they once did, causing some conservations to worry that they 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 are dependent on plants that have closed.