Endangered Florida manatee (Trichechus manatus)
Apart from mothers with their young, or males following a receptive female, manatees are generally solitary animals. Manatees spend approximately 50% of the day sleeping submerged, surfacing for air regularly at intervals of less than 20 minutes. The remainder of the time is mostly spent grazing in shallow waters at depths of 1–2 metres (3.3–6.6 ft). The Florida subspecies (T. m. latirostris) has been known to live up to 60 years.
Generally, manatees swim at about 5 to 8 kilometres per hour (3 to 5 mph). However, they have been known to swim at up to 30 kilometres per hour (20 mph) in short bursts.[
Intelligence and learning
Manatees are capable of understanding discrimination tasks and show signs of complex associative learning. They also have good long-term memory. They demonstrate discrimination and task-learning abilities similar to dolphins and pinnipeds in acoustic and visual studies.
Manatees typically breed once every two years; generally only a single calf is born. Gestation lasts about 12 months and to wean the calf takes a further 12 to 18 months.[
Manatees emit a wide range of sounds used in communication, especially between cows and their calves. Their ears are large internally but the external openings are small, and they are located four inches behind each eye. Adults communicate to maintain contact and during sexual and play behaviors. Taste and smell, in addition to sight, sound, and touch, may also be forms of communication.[
Manatees are herbivores and eat over 60 different freshwater ( e.g. floating hyacinth, pickerel weed, alligator weed, water lettuce, hydrilla, water celery, musk grass, mangrove leaves) and saltwater plants (e.g. sea grasses, shoal grass, manatee grass, turtle grass, widgeon grass, sea clover, and marine algae). Using their divided upper lip, an adult manatee will commonly eat up to 10%–15% of their body weight (about 50 kg) per day. Consuming such an amount requires the manatee to graze for up to seven hours a day. To be able to cope with the high levels of cellulose in their plant based diet, manatees utilize hindgut fermentation to help with the digestion process. Manatees have been known to eat small numbers of fish from nets.[
Manatees use their flippers to “walk” along the bottom whilst they dig for plants and roots in the substrate. When plants are detected, the flippers are used to scoop the vegetation toward the manatee’s lips. The manatee has prehensile lips; the upper lip pad is split into left and right sides which can move independently. The lips use seven muscles to manipulate and tear at plants. Manatees use their lips and front flippers to move the plants into the mouth. The manatee does not have front teeth, however, behind the lips, on the roof of the mouth, there are dense, ridged pads. These horny ridges, and the manatee’s lower jaw, tear through ingested plant material.
Manatees have four rows of teeth. There are 6 to 8 high-crowned, open-rooted molars located along each side of the upper and lower jaw giving a total of 24 to 32 flat, rough-textured teeth. Eating gritty vegetation abrades the teeth, particularly the enamel crown; however, research indicates that the enamel structure in manatee molars is weak. To compensate for this, manatee teeth are continually replaced. When anterior molars wear down, they are shed. Posterior molars erupt at the back of the row and slowly move forward to replace these like enamel crowns on a conveyor belt, similarly to elephants. This process continues throughout the manatee’s lifetime. The rate at which the teeth migrate forward depends on how quickly the anterior teeth abrade. Some studies indicate that the rate is about 1 cm/month although other studies indicate 0.1 cm/month.
More about these gentle sea creatures in Part 3 of this series!
from Wikipedia, the free encyclopedia)