Manatee
| Manatee | |
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| Manatee with calf. | |
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| Family: | Trichechidae Gill, 1872
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| Genus: | Trichechus Linnaeus, 1758
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| Species | |
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Trichechus inunguis | |
Manatees (family Trichechidae, genus Trichechus) are large aquatic mammals sometimes known as sea cows. The Trichechidae differ from the Dugongidae in the shape of the skull and the shape of the tail. Dugongs have a forked tail, similar in shape to a whale's, while manatees' tails are paddle-shaped. They are herbivores, spending most of their time grazing in shallow waters, and can weigh anywhere from 500 to 1000 kg.
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, African manatee). They spend half of their day sleeping in the water, surfacing for air every 20 minutes.
Vulnerability
All three species of manatee are listed by the IUCN as Vulnerable to extinction. Although it does not have any natural predators, human expansion has reduced its natural habitat in the coastal marsh areas and many manatees are injured or killed by collisions with powerboats. Manatees occasionally ingest fishing gear (hooks, metal weights, etc.) during feeding. These foreign materials do not seem to harm manatees, except for monofilament line or string. This can get clogged in the animal's digestive system and slowly kill the animal. Manatees can also be crushed in water control structures (navigation locks, flood gates, etc.), drown in pipes and culverts, and are occasionally killed from entanglement in fishing gear, primarily crab pot float lines. Manatees are also vulnerable to red tides, blooms of algae which leach oxygen from the water.
Manatees were commonly hunted for their meat by natives of the Caribbean, although this is much less common today. [1] Commercial meat farming of manatees has been suggested as a possible way to support the preservation of the species.
On June 8 2006, the manatee was removed from Florida's endangered species list, and now has a "threatened" status in that state. While none of the state laws protecting manatees have changed, many wildlife conservationists are not pleased with the removal decision.[2]. Manatees remain classified as "endangered" at the federal level.
Habitat
Manatees typically inhabit warm, shallow, coastal estuarine waters. Manatees often congregate near power plants, which warm the waters. Some have become reliant on this source of unnatural heat and have ceased migrating to warmer waters. Some power plants have recently been closing and the U.S. Fish and Wildlife Service is trying to find a new way to heat the water for these manatees.
The main water treatment plant in Guyana has four manatees that keep storage canals clear of weeds.
The natural source for warm waters for manatees during the winter is spring fed rivers. The West Indian Manatee migrates into Florida rivers such as the Crystal River, The Homosassa River and The Chassawohitzka River. The head springs of these rivers maintain a water temperature of 72 degrees year round. During the winter months, November to March, approximately 400 West Indian Manatees (According to the National Wildlife Refuge Service) congretate in the rivers in Citrus County, Florida.
Manatees have been spotted as far north as Rhode Island. [1].
Disposition
Manatees are slow moving, non-aggressive, and generally curious creatures. They enjoy warmer waters and are known to congregate in shallow waters, [3] and frequently migrate through brackish water estuaries to fresh water springs. Their slow moving, curious nature, coupled with the dense concentration of humans along coastlines, has led to the species being damaged or killed by boat propellers. As a result, most all manatees in the wild have propeller scars on their backs. For many, the cuts lead to infections which later prove fatal. Broken ribs and punctured lungs resulting from collisions also cause many deaths. This proximity to humans also frequently leads people to seek out interaction with manatees.
Diet
Manatees are herbivores and eat over 60 different plant species such as mangrove leaves, turtle grass, and types of algae, using their divided upper lip. An adult manatee will commonly eat up to 9% of its body weight (approx 50kg) per day. Antillean manatees have been known to eat fish from nets.
Captivity
The currently oldest manatee in captivity is Snooty who is held at the South Florida Museum. He was born at the Miami Seaquarium on July 21 1948 and came to the South Florida Museum in Bradenton, Florida in 1949, where he still lives.
Manatee Hunting
Manatees have been hunted by Carribean people for hundreds of years. When Christopher Columbus arrived in the region, manatee hunting was already an established trade. Native Americans hunted manatees to make war shields, canoes, and shoes, though the manatee was predominately hunted for its abundant meat, which could often feed a village for days. When Roman Catholic pioneers settled in the region, manatees were a welcome meal for them. This is because due to religious beliefs, they could not eat meat on Fridays. However, the manatee was classified as a fish, as it lived the water- thus it could be eaten on Fridays. Manatees were also hunted for their valuable bones, as they were used to make "Special Potions." Up until the 1800's, museums would pay as much as 100$ for manatee bones or a manatee hide- an astronomical amount at the time. Though it became illegal to hunt manatees in 1893, this did not stop poachers. Nowadays, manatee meat is a delicacy, albeit an illegal one.
Cultural references
- It is thought that sailors created the myth of the mermaid after mistaking manatees for half-fish, half-human creatures.
- Manatees' popularity is steadily growing, as is shown by references to them in popular shows such as South Park, The Simpsons, Family Guy, the popular webcomic Questionable Content and the appearance of many non-profit organizations which benefit manatees.
References
- Shoshani, J. (2005). Wilson, D.E.; Reeder, D.M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 93. ISBN 978-0-8018-8221-0. OCLC 62265494.
- ^ "Massive Manatee Is Spotted in Hudson River". New York Times. August 7, 2006.
External links
- Bagheera An educational website of Earth's endangered animals
- http://www.geocities.com/philgarringer/St_Lawrence_manatee.html A website dedicated to protecting the Northern Manatee