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The sirenians are an order of marine placental mammals with four known living species. The name of this group denotes mermaids, due to their resemblance to these beings when they are nursing their young. The truth is that mermaids have never existed, but their legend comes from this ancient confusion. Currently, there are only two living families: Dugongidae Y Trichechidae.
The main Characteristics of Sirenian Mammals and Examples, as well as other data about this group, are treated in this Green Ecology article.
Physical characteristics of the sirenians or sirenids
Here we explain the main characteristics of sirenian mammals:
Sirenians size
Sirenians are mammals completely adapted to marine life, with front legs completely transformed into fins and very reduced hind legs. Its size is extremely large, measuring between 2.5 and 4 meters, and its body is cylindrical in shape. They are also very heavy animals, with a weight that oscillates between 250 kg and 1.5 tons.
Fins
These animals do not have a dorsal fin (as distinguished from cetacean mammals) and the tail has been turned into a fin horizontal. They have a modified skin muscle as the main propellant of the caudal fin. The shape that this fin acquires is variable and is the main differential characteristic between both families, dugongs have a crescent shape, while manatees have a circular or shovel shape.
Skin
Is thick and wrinkled, except in those of tropical waters, in which the epidermis is thin. Adults possess little hair, limited to a region near the mouth and some on the trunk, while embryos and neonates have more fur.
Teething and digestive system
Teething is one of the differences between sirenian families. In manatees, the incisor teeth are very reduced, while in dugongs, they form a small tusk in males (in females they do not protrude from the jaw). They do not have canine teeth.
With regard to the digestive system, it is extremely long (it measures 20 times the body length. Digestion takes place in the intestine, while chewed food is stored in the stomach and the bulb (protrusion of the stomach).
Skull and skeleton
Sirenian bones are very dense and heavy, with few channels and pores. They have little flexibility, so it is very easy for them to break. The skull gives them an elongated face formed by the incisor bone.
Distribution, behavior and feeding of sirenians
Sirenian mammals today live in tropical waters, sometimes in very distant regions between the different species. Thus, we have that the only species of the family Dugondidae, the dugongDugon dugon) can only be found in the waters near the Indian coast, for example, the Red Sea.
Regarding the family Trichechidae, exist 3 species of manatees:
- Caribbean manatee: can be found in an area of the Mexican Gulf, in the southeastern United States, off the coast of Florida and on the northern coast of South America
- Amazonian manatee: can be found in the Amazon River region and South America
- African manatee- Can be found in the Niger River and other rivers in western Africa
Sirenians are very large, heavy, and slow-moving marine mammals. Regarding their behavior, they stand out for their docility. This fact makes them easy prey for hunting, in which their meat and skin are sought, and has led them to the danger of extinction, which is why they are currently protected species.
Sirenian animals they are generally herbivores. They eat grass, algae, and marine plants. Those that inhabit mangroves, also feed on the leaves that may be close to them. Manatee require the intake of between 45 and 78 kg of food daily and they spend about 6 to 8 hours a day eating, foraging near the surface, while dugongs feed only in the deep sea. It is possible that they involuntarily ingest small invertebrates, from which they extract the necessary proteins. In addition, in the specimens that have been born and raised in captivity, they include fish in their diet without major problem.
Examples of sirenians or sirenids
The sirenians or sirenians are divided into two families:
Dugondidae or dugongs
Only one current species, the dugong, is known to live specifically in the Indian Ocean and northern Australia, including the Red Sea. They do not live in waters with temperatures below 20 ºC or in fresh waters.
Trichechidae or manatees
Only three species of manatees are known, although a fourth is believed to exist (without scientific consensus), the dwarf manatee, whose length is approximately 1.3 meters. Manatees are also called sea cows and their name means 'gif.webpted with hands' in Latin, as sailors confused their fins with hands.
Without a doubt, the sirenians are a very amazing order of marine mammals and it is important to know them and raise awareness for their protection.
If you want to read more articles similar to Sirenian mammals: characteristics and examples, we recommend that you enter our Wild Animals category.
