Manatees
Manatees are large, aquatic mammals belonging to the family Sirenia, characterized by their streamlined bodies and paddle-shaped tails. There are four recognized species, including the Florida manatee (Trichechus manatus latirostris), the Antillean manatee (Trichechus manatus manatus), the West African manatee (Trichechus senegalensis), and the Amazonian manatee (Trichechus inunguis). They inhabit various aquatic environments, with the Florida manatee primarily found in the coastal waters of Florida and occasionally in the southeastern U.S., while other species are distributed across regions from Africa to South America.
Manatees are gentle herbivores, consuming a diet of aquatic plants that constitutes 4 to 9 percent of their body weight daily. They are known for their slow movement, typically traveling at 2 to 6 miles per hour, and can stay submerged for about 20 minutes, although they surface every few minutes for air. Socially, manatees are often seen in small groups, particularly around warm water sites during colder months, and females typically raise their calves for up to two years.
Despite their resilience, manatees are currently listed as vulnerable due to threats such as habitat destruction and injuries from boats. Conservation efforts are essential to ensure the survival of these unique creatures, which can live up to 60 years in the wild.
Manatees
Manatee Facts
Classification:
- Kingdom: Animalia
- Subkingdom: Bilateria
- Phylum: Chordata
- Subphylum: Vertebra
- Class: Mammalia
- Subclass: Eutheria
- Order: Sirenia
- Family: Trichechidae (manatees)
- Genus and species:Trichechus manatus (West Indian manatee or American manatee, with subspeciesT. manatus latirostris, the Florida manatee, andT. manatus manatus, the Antillean manatee);T. senegalensis (African manatee);T. inunguis (Amazonian manatee or South American manatee)
- Geographical location: Florida, Caribbean, and northern South America; West Africa; Amazon River basin
- Habitat: Warm tropical and subtropical water, including shallow coastal waters, estuaries, and rivers
- Gestational period: Approximately twelve months
- Life span: Twenty-eight years in the wild; fifty to sixty years in captivity
- Special anatomy: Flat, paddle-shaped tail; two pectoral flippers; nasal openings at the top of the snout; large, flexible upper lip equipped with vibrissae attached separately to nerve endings and each with its own blood supply
The Florida manatee (Trichechus manatus latirostris) is found primarily in the Florida peninsula, but can occasionally be sighted as far north as Virginia and west to Mississippi. The Antillean manatee (Trichechus manatus manatus) shows a patchy distribution, including northeastern South America, southern Texas, Mexico, and the Caribbean. Trichechus senegalensis, the West African manatee, can be found on the west coast of Africa from Senegal to Angola. The Amazonian manatee, Trichechus inunguis, is found throughout the Amazon river drainage basin.
The species are distinguished by their geographical distributions, and while they are physically very much alike, some differences exist. Manatees all exhibit a streamlined body, full around the middle with no visible neck, tapering to a paddle-shaped tail used for propulsion. They have two small pectoral flippers on their upper bodies that are used for steering and bringing food to the mouth. The lips are long and flexible, and help in funneling plants into their mouths. Manatees are grayish-brown in color and have sparse, bristly hair scattered thinly over their torsos. They have molars at the back of their mouths, and unlike most other mammals, as the front molars wear down they are continually replaced by new teeth from the back of the mouth. Adult West Indian and West African manatees average about ten feet in length and weigh approximately 800 to 1,200 pounds. Amazonian manatees are smaller, shorter, and more slender, averaging about eight feet in length and less than eight hundred pounds.
Adapted for the Aquatic Life
Streamlined bodies and flippers are ideal for the aquatic life of a manatee. They are agile and typically cruise in search of food at speeds of two to six miles per hour, but can swim as fast as fifteen miles per hour. While they have been sighted diving to depths of about thirty-three feet, they primarily forage for food no deeper than ten feet. Manatees can stay underwater for up to twenty minutes, but typically surface every two to three minutes for air.
Manatees spend most of their day foraging for aquatic plants and will consume between 4 and 9 percent of their body weight in wet vegetation daily. The animals are nonaggressive and nonterritorial and spend the rest of their time traveling, investigating objects, and socializing. Manatees are considered semisocial, and the typical social unit is a female and her calf; however, congregations of up to two hundred individuals can be found near warm water sources such as power plant outfalls and hot springs, especially during winter months.
Male manatees are sexually mature at about nine to ten years of age, and females at about seven to eight years. Mating takes place in the water, and the female is accompanied by, and mates with, several males. Gestation takes about twelve months; the newborn calf measures about four feet and weighs sixty to seventy pounds. Calves remain close to their mothers for up to two years. The calf is dependent on its mother for nutrition, and for learning about feeding and resting areas, migratory routes, and warm water refuges. It is believed that manatees can live to sixty years in the wild; however, habitat destruction and injury by boats and fishing lines endanger manatees worldwide. The International Union for Conservation of Nature and Natural Resources has listed all three manatee species as vulnerable since the mid-2000s.
Principal Terms
metazoa: organisms which are multicellular
molars: flat, stout teeth used for grinding food
notochord: longitudinal, flexible rod located between the gut and nerve cord
placenta: structure that connects a fetus to the mother’s womb; indicative of internal gestation of young
sirenian: refers to animals in the family Sirenia, the only completely aquatic herbivorous mammals; the two families, those of the dugongs (Dugongidae) and manatees (Trichechidae), contain five species
vibrissae: whiskers or bristles, used to provide positional information to an animal
Bibliography
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