The manatee, belongs to the family Trichechidae and is a fully aquatic marine mammal. Sometimes known as sea cows, they make up three of four of the order of Sirenia. The Sirenia currently comprise two distinct families: Dugongidae (the dugong and the now extinct Steller’s sea cow) and Trichechidae.
These wonderful animals are really interesting to look at, and even more interesting to learn about. Keep reading on to find out all you need to know about the manatee.
Despite being nicknamed the sea cow, manatees actually more closely resemble an elephant. Large and gray, the average adult is about 10 feet long and weighs between 800 and 1,200 pounds. Females tend to be larger and heavier than males. At birth, baby manatees weigh about 30 kg (66 lb) each.
Their bodies are round and taper to a flat, paddle-shaped tail, which differentiates them to the dugong, which has a fluked tail, similar to a whale. They have front flippers, each with three to four “fingernails”, except the Amazon manatee, which has no nails (its Latin species name “inunguis” means “without nails”). The bones in the flippers are similar to a human hand, with jointed finger bones.
Manatee skeletons are made of very dense bone, which gives the animal neutral buoyancy, meaning its physical body density is equal to the water in which it swims. They also only have six neck vertebrae, while most other mammals have seven. This means that they cannot turn their head and must turn their entire body to see what’s going on behind or to the side of them.
The female also has two teats, one under each flipper, which is a characteristic that was used to make early links between the manatee and elephants.
A manatee’s eyes appear to be small, but their vision is actually very good. They are able to distinguish different sized objects, colors, and patterns. Their eye muscles close in a circular motion, like an aperture on a camera.
Their mouths contain no more than six teeth at one time, and their teeth are called “marching molars” because they are replaced throughout life as they wear down from the abrasive diet or fall out. They also have no incisor or canine teeth. Their upper lip is large and flexible and allows them to gather food.
While the sensory system of a manatee has not been well studied, it is thought they have excellent hearing. Despite not having outer ear structures, they have large inner ear bones and it is thought these help them to communicate with each other. Manatees emit chirps, whistles, and squeaks, all of which indicate how they are feeling to other manatees, even when the water is murky.
Manatees have a large cecum despite their simple stomach, and their intestines are about 45 meters long, which is unusually long for the manatee’s size. The large cecum allows them to digest tough plant matter.
Amazonian manatees are the smallest of the three species. These are shorter and more slender than the Indian variant. The longest recorded specimen measured 9.2 feet. (2.8 metres). One particularly large specimen weighed 480 kilograms (105 pounds).
Manatees have been known to live for up to 60 years.
Manatees are herbivores and eat over 60 different freshwater and saltwater plants. In fact, they eat between 100 to 150 pounds of underwater greens a day and, because they are large, they must feed for almost half of the day. This equates to them eating around 10 to 15 percent of their body weight every day. Manatees have been known to eat small numbers of fish from nets.
To gather food, they use their flippers to “walk” along the bottom whilst they dig for plants and roots. When they find a plant, they use their flippers to scrape the plant towards their mouth, and their lips, which the upper half of is split, use seven muscles to move.
Manatees are slow-moving animals and are very gentle. They are generally solitary animals and spend their days eating, resting, and traveling. Around 50% of their time is spent sleeping. It has been said that, if you spot a group of manatees, it is likely to be a mating hard because they usually swim alone or in pairs. When they are in pairs or groups, they sometimes use their flippers to touch and soothe each other.
Because they are mammals, they must surface every so often for air. This usually happens every three to five minutes, but if they are using a lot of energy, it could be as often as every thirty seconds. On the flip side, if a manatee is resting, they have been known to stay submerged for as long as twenty minutes! When they do take a breath, 90 percent of the air in their lungs is replaced! Humans only replace about 10 percent.
A manatee usually stays just below the surface of the water, at depths of around 1–2 m (3 ft 3 in–6 ft 7 in), which is often the reason they are hit by boats and have collisions with other vessels.
While these mammals are mostly slow-moving, they can be swift, too. They usually travel as a pace of about 5 miles per hour (8 kilometers per hour), but can go as fast as 15 miles per hour (24 kilometers per hour). They also have a very good long term memory.
Healthy manatees have no natural predators, although alligators, crocodiles and sharks may prey on young or weak manatees. They are also hunted for their meat in West Africa. When threatened, the manatee’s response is to dive as deeply as it can, which suggests that their biggest threat comes from boats and humans instead of other sea creatures.
Manatees breed around once every two years and normally only one calf is born. Their gestation period is around 12 months and it takes around 12 to 18 months to wean a calf. Females may be courted by around 12 different males, and, once a male has mated, he has no part in raising the young.
Newborns can swim about an hour after they are born. They become mature at about five years old.
Manatees live in coastal waters, slow-moving rivers, estuaries, lagoons and saltwater bays, and will migrate to warm waters in the winter. African manatees live along rivers and coasts of western Africa, the Amazon manatee lives in the Amazon River’s drainage, from the headwaters in Colombia, Peru, and Ecuador to the mouth of the Amazon in Brazil, and the West Indian or American manatee lives in the southern and eastern US, often Florida.
Both West African and West Indian manatees need water that is at least 60 degrees Fahrenheit (15.6 degrees Celsius), which is down to the fact they have a low metabolic rate and minimal fat layer. These two species also have an internal regulation system that works with the kidneys to keep salt concentrations at manageable levels, which allows them to live in both salt water and fresh water. On the other hand, Amazon manatees are restricted to fresh water.
Unfortunately, the International Union for Conservation of Nature (IUCN) Red List of Threatened Species lists all three species as vulnerable and decreasing in numbers.
Manatees were actually among the first creatures listed on the Endangered Species Preservation Act of 1966. Luckily, over the years, conservation efforts has decreased the manatee mortality rate and allowed them to be declared as “vulnerable”, which means they are still protected under the Endangered Species Act, but not considered “endangered”.
The population is affected by climate change, pollution, and human activities. They need clean oceans and areas of sea with boat speed zones to continue to help them thrive.
Manatee Fun Fact!
Because algae thrives in wet areas with lots of sunlight and manatees swim just below the surface of the water, the manatee’s back is an ideal breeding ground for algae! Fortunately, algae helps to block out harmful rays from the sun.
- They have a streamlined body – full around the middle and narrowing to a paddle-shaped tail.
- Manatees are a greyish-brown colour, however, Amazonian manatees usually have white or pink patches on the belly and chest. Organisms such as algae, which may grow on the skin of these slow-moving individuals, help determine their colouration.
- They have two small pectoral flippers on their upper body which are used for steering. These flexible flippers may also be used for bringing food to the manatees mouth and for guiding movement along a waterways bottom.
- Manatee flippers have five digits that are covered by a thick layer of skin. This bone structure is similar to that of toothed whales, seals, and sea lions. They have no externally visible neck.
- They do not have external ear flaps and the opening to the ear canal is very small.
- They have two nostrils that lie on top of the head at the end of the snout.
- Manatees have a large flexible upper lip. Their lips help guide vegetation into their mouth. Vibrissae (whiskers) are found on the surface of this lip.
- The only teeth are 24 to 32 molars located in the back of the mouth.
- They swim by moving their large paddle like tail in an up-and-down motion.