The Dugongs and manatees Animal Dugongs and manatees Sirenians – the dugong and manatees are large, slow-moving creatures with a streamlined body. They are the only marine mammals that feed primarily on plants.
Sirenians must rise to the surface to breathe, but they can remain submerged for up to 20 minutes. Even though they have no enemies apart from humans, all the sirenians may number less than 150,000 making them among the least abundant of any mammal order.
- PHYLUM: Chordata
- CLASS: Mammalia
- ORDER: Sirenia
- FAMILIES: 2
- SPECIES: 4
Sirenians have paddle- like front limbs and a flat tail to aid propulsion. Their skin is thick and tough, and they have a relatively small brain. Due to the large volume of gas given off during the digestion of plant matter, sirenians are highly buoyant.
To compensate, their bones are heavy and dense. Under water, sirenians can close their nostrils. They lack well-defined eyelids and protect the eye surface with secretions and by drawing the nictitating membrane across the eye.
Sirenians strip vegetation using their large, mobile upper lip. Food is then crushed between horny plates on the front part of the palate and on the lower jaw, and finally ground between the teeth.
Mother and half
Sirenians are slow breeders: usually only one calf is produced every 2 years. The “mouthing” contact between this manatee mother and calf helps to preserve the family bond.
FORAGING ON THE SEA BED
Sirenians, such as this dugong, frequently search the sea bed for the rhizomes (underground stems) of sea grasses, which have high concentrations of carbohydrates.
In the past, sirenians were hunted extensively for their meat, hide, and oil. Today, they are vulnerable to injury or death caused by boat propellers (below), fishing nets, and the pollution of coastal waters.