Sirenian mammals: characteristics and examples

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 short 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, weighing between 250 kg and 1.5 tons.

Fins

These animals do not have a dorsal fin (unlike cetacean mammals) and the tail has been turned into a horizontal fin . 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

It is thick and wrinkled , except in tropical waters, where the epidermis is thin. Adults have 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.

Sirenian mammals today inhabit tropical waters , sometimes in very distant regions between different species. Thus, we have that the only species of the Dugondidae family , the dugong ( Dugon dugon ) can only be found in the waters near the Indian coast, for example, the Red Sea .

As for the Trichechidae family , there are 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 are generally herbivores . They feed on grass, algae, and marine plants. Those that inhabit mangroves also feed on the leaves that may be close to them. Manatees require the intake of 45 to 78 kg of food per day and spend about 6 to 8 hours a day eating, foraging near the surface, while dugongs forage only in the depths of the 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.

The sirenians or sirenians are divided into two families:

Dugondidae or dugongos

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 ‘gifted with hands’ in Latin, as sailors mistook their fins for 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.

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