Manatees, often referred to as “sea cows,” are large, gentle marine mammals known for their docile nature and unique appearance. These magnificent creatures belong to the order Sirenia, which includes three species: the West Indian manatee, the Amazonian manatee, and the West African manatee. Among these, the West Indian manatee is commonly found in North American waters.
Manatees are well-adapted to their aquatic habitat, with paddle-like flippers, streamlined bodies, and an absence of hind limbs. They are known for their slow and peaceful nature, spending much of their time grazing on aquatic vegetation in shallow coastal areas, rivers, and estuaries. While once heavily endangered, conservation efforts have played a crucial role in safeguarding these gentle giants.
- North American manatees are the same species as the West Indian manatee.
- The manatee in North America is the most prominent member of the aquatic mammal order Sirenia.
- The North American manatee is distinct from the Amazonian and the African manatee.
- Recent genetic research suggests that the West Indian manatee consists of three groups, which are geographically distributed.
- In the 1970s, the North American manatee was listed among the endangered species. At that time, there were only a hundred left.
- To be able to conserve the North American manatee, it has been of significant conservation to federal, state, private, and nonprofit organizations to protect these species from natural and human-induced threats such as collisions with boats.
- The average North American manatee is about 2.7-3.5 m long and weighs 200-600 kg.
- The female North American manatee is different from most mammals because it is larger than the males.
- Manatees are mammals; hence, they breathe air, have warm bodies, have hair, and give birth to live young.
- The North American manatee has adapted fully to aquatic life, having no hind limbs.
- Manatees have a spatula-like paddle for propulsion in the water instead of hind limbs.
- The manatees have decreased resistance in the aquatic environment due to their evolved streamlined bodies, which lack external ear flaps.
- Manatee skin is grey, but this can vary due to coloration with algae and other biotas like barnacles.
- Manatees are easy to identify because their scar tissue is white and persists for decades.
- The manatee is unique in comparison to other mammals. They have a longitudinally oriented diaphragm that splits in half to form two Hemi diaphragms, and each membrane is independent of muscular contractions.
Habitat and Behavior
- The North American manatees live in shallow coastal areas.
- The manatee is known to withstand significant changes in water salinity and has been found in shallow rivers and estuaries.
- The North American manatee can live in fresh, salty, and saline water.
- The North American manatees have a prehensile snout for grabbing vegetation and bringing it into their mouths.
- The manatee has six to eight molariform teeth in each jaw quadrant.
- The manatee’s bone is dense and reliable, which allows them to act as ballast and promote negative buoyancy.
- The manatees can float, as there are two opposing buoyancy in the manatee’s body, negative buoyancy, and positive buoyancy, which comes from their high-fat content. These two buoyancy counterparts and the air in the lungs help manatees achieve neutral buoyancy in the water.
- The North American manatees are limited to the tropics and subtropics due to a meager metabolic rate and lack of a thick layer of insulating body fat.
- The North American manatee is agile in water, and individuals have been seen doing somersaults and even swimming upside-down.
- The manatees have no territory barriers and do not have complex predator avoidance behavior; they have evolved in areas without natural predators.
- The manatees share the characteristic of exceptional communication with their relative, the elephant.
- Scientists say that manatees form long mating periods, heard when wandering males come across estrous females. This indicates the possibility that males can sense estrogen or other chemical indicators from females.
- Manatees communicate information to each other through their vocalization patterns, according to scientists.
- Female and male manatees differ in that there are sex and age-related differences in the vocalization structure of universal squeaks and screeches in adult males, adult females, and juveniles.
- There is an increase in manatee vocalization after a vocal playback stimulus, indicating that they can recognize another individual manatee’s voice.
- The manatees exhibit human characteristics when communicating in a loud environment. They will involuntarily increase their vocal effort when speaking in noisy environments.
- The manatees eat other manatees’ feces. Manatees do so to gather information about their reproductive status or dominance.
Diet and Feeding
- The manatee feeds on plants and is an herbivore. Manatees feed on over 60 species of aquatic plants in both fresh and saltwater.
- Manatees may also feed on grass and leaves when the tide is high enough.
- The North American manatees also feed on some fish and invertebrates.
- The manatee’s eating capacity is dependent on its size and activity level.
- Per day, the manatee will graze for five or more hours consuming anywhere from 4% of their body weight in wet vegetation.
- The manatee is a non-ruminant with an enlarged hindgut.
- The manatee has a large gastrointestinal tract, with contents measuring about 23% of its total body mass.
- The manatee has sensitive tactile hairs that cover their bodies and faces, referred to as vibrissae.
- The vibrissae are blood-filled sinuses bound by a dense connective tissue capsule with sensitive nerve endings that provide haptic feedback to the manatee.
- Most vibrissae in mammals are located on the facial regions of terrestrial and non-sirenian aquatic animals. They are also called whiskers.
- The manatee’s mouth consists of very loose prehensile lips that grasp food and objects.
- The manatee uses the vibrissae on the lips to locate vegetation after turning the whiskers outward when grasping.
- The vibrissae in manatees are essential as they can perform active touch discrimination of textures and navigate the turbid waters of their environment.
- Research shows that the manatee uses the vibrissae to detect hydrodynamic stimuli like fish use their lateral line system.
Reproduction and Family Structure
- Despite North American manatees mostly being solitary creatures, they form mating herds while in estrus.
- The female manatee first breeds successfully between the ages of seven and nine. However, they are capable of breeding as early as the age of four.
- The male manatee reaches sexual maturity at three to four, earlier than female manatees.
- Manatees have a gestation period of 12 to 14 months.
- The female manatee usually gives birth to one calf, but on rare occasions, they give birth to two.
- The newborn calf already has molars and can consume seagrass within the first three weeks of birth.
- Manatees will have an average of five and seven offspring between the ages of 20 to 26.
- The newborn calf weighs 60-70 lbs and grows up to 4 to 4.5 ft.
- The manatee lives in a family unit consisting of a mother and calf, and they remain together for up to two years.
- The male manatee gathers in mating herds around a female when she is ready to breed but contributes no parental care to the calf.
Threats and Conservation Efforts
- The North American manatee has been hunted for hundreds of years. They are hunted for meat and hide.
- The manatee is in danger due to environmental stress, such as red tide and cold waters, which cause health problems to manatees, such as immunosuppression and even death.
- The manatee’s death is also a result of both large and small boats. Boats hit them, and they can die instantly.
- Manatees are not able to quickly move away from an oncoming boat.
- The manatee is found mainly in shallow coastal areas and rivers. They live in these areas because they can discover seagrass, mangrove leaves, and algae to eat.
- North American manatees spend their lives on the cusp between salty and fresh water. They can maintain the correct balance in their bodies through an internal regulation system that works with the kidneys to ensure salt concentrations never get too high.
- North American manatees live in warm water, which is essential.
- Manatees have metabolic rates and minimal fat to protect them from cold water; they stick to 60 degrees or warmer water.
- Although manatees look insulated, the most significant part of their body comprises their stomach and intestines.
- During cold seasons, the manatees find their way to warm river tributes or water outputs from local power plants.
- Manatees go to the surface of the water every three to five minutes to breathe. They can remain under the water for up to 20 minutes.
- The manatees have no natural predators in the wild. Humans are the only species that have endangered the existence of manatees.
- Manatee’s brains are smooth, and the ratio of their brain to their body size is the lowest of any mammal.
- Manatees are believed to be sirenians. Out of that, Sirenians are animals in the Order Sirenia, which includes manatees and extinct sea cows.
- The manatee communicates with squeaking, squealing sounds. They are vocal animals with individual vocalizations.
- The manatee makes sounds to communicate fear or anger when socializing and finding each other, such as a calf looking for its mother.
- Manatees communicate through touch, sound, smell, taste, hearing, and sight.
- Manatees have an average lifespan of 40 years.
- Scientists believe that the manatee has evolved from a four-legged land mammal that lived sixty million years ago.
- Manatees have good sight and excellent hearing capabilities. They can hear something approaching while it is far away. They can easily see sea plants under the water.
- Their eyes are small and have a special membrane to protect their eyes. The seawater vegetation does not easily damage their eyesight.
- Manatees lack outer ear structures, but they have large inner bones, which assist in their excellent hearing ability.
- The manatee cannot quickly turn their heads sideways. Unlike other mammals, the manatee has six neck vertebrae, whereas most have seven.
- Manatee comes from the Carib word MANTI, meaning breast or udder.
- The manatee has a powerful tail they use to swim for short bursts at 15 mph.
- Manatees are nearsighted and can see in blue, green, and gray but not in red or blue-green combinations.
- Manatees utilize most of their time eating, resting, and traveling.
- North American manatees are protected under federal law by the Marine Mammal Protection Act of 1972 and the Endangered Species Act of 1973.
- Manatee hunting is illegal in North America. No one is allowed to hunt, capture, or kill a manatee. Violating these laws could lead to a conviction for civil or criminal acts.
- Manatees cannot survive in cold water. Therefore when it is hard, manatees migrate to shallow, slow-moving rivers, bays, estuaries, and coastal waters.
- Manatees move freely around the Florida rivers and coastal waters in the summer. This is because of the warmer waters.
- The manatee is one of the marine animals, and its skeleton is available for tourists to view at the North Carolina Museum OF Natural Science in Raleigh, North Carolina.
- Manatees will eat up to 1/10th of their body weight in 24 hours, around 59 kilos.
- Manatees are also called sea cows.
- Manatees are sizeable marine mammals with strange egg-shaped heads, flat tails, and flippers. Their flippers are essentially their forearms.
- The manatee has a close relative on land, the elephant.
- The manatee can grow big. They can grow up to 13 feet long, but usually, they are up to 8 feet long.
- The manatee can weigh as much as 200 to 600 kilograms.
- The North American manatees are primarily found in sea and ocean waters and rarely in river-flowing waters.
- The manatees are not territorial by nature and do not have a group leader. They prefer to stay alone or sometimes in pairs.
- When manatees come together in one place, it is usually to enjoy an abundant supply of food and enjoy warmer waters.
- Manatee conservation is advocated for as their population could be at risk.
- Humans contribute significantly to the endangerment of manatees through activities conducted in their habitats.
- There are dedicated organizations and rescue teams that work tirelessly to rescue and rehabilitate injured or stranded manatees. These efforts play a crucial role in the conservation of the species.
- Archaeological discoveries have revealed that manatees have been a part of human history for a long time. Artifacts like ancient pottery and carvings depict manatees, showing their significance in various cultures.
- Manatee tourism has become a significant industry in some regions where these gentle creatures are prevalent. Tourists have the opportunity to observe manatees in their natural habitat while following guidelines to ensure their safety and protection.
For information on the West Indian Manatee, please click here.
Bryan Harding is a member of the American Society of Mammalogists and a member of the American Birding Association. Bryan is especially fond of mammals and has studied and worked with them around the world. Bryan serves as owner, writer, and publisher of North American Nature.