Manatee characteristics, habitat, feeding, behavior

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Anthony Golden
Manatee characteristics, habitat, feeding, behavior

The sea ​​cow (Trichechus) is a marine mammal that is part of the Trichechidae family. In this species, the front limbs are transformed into fins and the hind limbs are completely absent. In replacement of these, it has a flat tail, which it uses to propel itself in swimming..

One of its most outstanding characteristics is its teething. First of all, this species does not have incisors or canines, only cheek teeth. These molars are adapted to grind up the highly fibrous plant material you consume.

Sea cow. Source: Cedricguppy - Loury Cédric [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]

On the other hand, because manatees feed on abrasive plants, their molars wear out, so they are continually replaced. The new teeth form at the back and progress as the others fall out..

The species of the genus Trichechus have a seasonal reproduction, with a long duration of the gestation period, between 12 and 14 months. This contributes to the slow growth of their populations, which are threatened with extinction..

In reproduction, the availability of food is an important factor. This is due to the fact that said abundance guarantees a sufficient energy reserve for the maintenance of pregnancy and for the lactation of the young..

Article index

  • 1 Evolution
    • 1.1 Species
  • 2 Features
    • 2.1 Vision
    • 2.2 Breathing
    • 2.3 Thermoregulation
    • 2.4 Whiskers
    • 2.5 Face
    • 2.6 Coloring
    • 2.7 Body
    • 2.8 Size
    • 2.9 Digestive system
    • 2.10 Teething
  • 3 Habitat and distribution
    • 3.1 Amazon manatee
    • 3.2 African manatee
    • 3.3 West Indian manatee
  • 4 Danger of extinction
    • 4.1 - Threats
    • 4.2 - Actions for your protection
  • 5 Taxonomy and subspecies
  • 6 Playback
  • 7 Food
  • 8 Behavior
  • 9 References

Evolution

The manatee is the only living member of the Trichechidae family that is related to the Dugongidae family. The two families make up the order Sirenia, whose closest relatives are the elephants of the Proboscidea group.

Sirenia is made up of a group of marine herbivorous mammals, which are completely aquatic. According to the fossil record, this order existed 50 million years ago, at the beginning of the Eocene and by the end of that period they had already diversified.

One of the most primitive sirenians is the Prorastomus, that lived in the Middle Eocene, around 40 million years ago. This, unlike the current sirenians, was terrestrial.

It had strong legs, a long tail, and was about 150 centimeters long. The characteristic of its teeth indicates that it fed on soft plants.

Another extinct genus is the Pezosiren that inhabited the planet 50 million years ago. Their lifestyle was similar to that of the hippopotamus, representing an example of the transition between land and marine mammals..

In relation to their skull characteristics and body structure, they are closely related to dugongs and manatees. However, they had four well-developed legs, adapted for walking on the ground..

When the Eocene ended, the Dugongidae family appeared, which had a streamlined body. Also, the front legs were fin-shaped, without hindlimbs, and with a caudal fin.

Species

The last of the synergistic families to evolve is the Trichechidae, which possibly arose from the first dugongs. Compared to its ancestors, the modern West Indian manatee has had little variation.

As for the African manatee, it has also preserved its ancestral form. This could have dispersed from South America to Africa, through the transoceanic currents. Amazonian manatees could be the product of isolated populations in an internal basin of South America.

Characteristics

NASA [Public domain]

View

The vision of the sirenians has been little studied. However, some researchers have shown that the Amazon manatee is capable of visually tracking underwater objects..

On the other hand, the Caribbean species has a dichromatic vision, thus distinguishing green and blue colors..

Breathing

Manatees rise to the surface to breathe. They do this by exhaling very hard when the animal comes out of the water and its nose emerges. In each breath, they fill their lungs with approximately 90% air, contrary to the man who only replenishes about 10%.

Thus, they can be kept submerged for up to 20 minutes. In these dives, the nostrils are sealed thanks to special folds. Although they can stay underwater for a long time, it is common for them to move out of the water to breathe approximately every five minutes.

Thermoregulation

To regulate body temperature, the body has special adaptations. Among these is the diversion of the peripheral circulation, which is in close contact with water. It also has a layer of subcutaneous adipose tissue that reduces heat loss..

Vibrisas

Trichechus has sensitive tactile hairs, known as vibrissae. These coat your face and body. Each hair has a capsule of connective tissue with innumerable nerve endings, which provides the animal with information about the environment.

Generally, animals that have these sensory structures have them in the face area, and they are called whiskers. However, in manatees they are found throughout the body. Those in the facial area are around 30 times denser than those in the rest of the body..

The vibrissae located on the lips turn outward during the grasping of the food and are used to locate the vegetation. Research indicates that vibrissae are highly sensitive, allowing manatees to discriminate tactile textures.

Thanks to these specialized hairs, this mammal can detect different hydrodynamic stimuli, which allow it to navigate efficiently in the murky waters of its environment..

Expensive

The brain is small, compared to the rest of the mammals that have a similar body size. The head of this Trichechus is small and its neck cannot be distinguished. It has a short, thickened and square muzzle. In the front are two semicircular nostrils.

As for the mouth, it has fleshy and prehensile lips. The upper one is larger and more flexible. Furthermore, it is deeply divided. Thus, you can move each side independently, while the animal feeds.

The lips are used to grasp food and other objects. In addition, they are used to communicate and in different social interactions.

Coloration

Generally, the skin is gray in color. However, many organisms and algae often grow in the body of this mammal, due to which the coloration may have a brown or greenish tint.

Externally, the African manatee cannot be distinguished from the American, since they have the same skin tones. However, the Amazonian manatee is different in that it has a bright pink or white patch on its chest..

Body

The manatee's body is sturdy and conical in shape. It ends in a flat, rounded tail, similar to a pallet, which is used to propel itself forward. The front limbs are modified in the form of fins and the hind limbs are not present.

The fins are flexible and contribute to the movement of the animal. Likewise, they use them to scratch themselves, to touch objects, to move food from one side to the other and to clean their mouths. Even with these, they can hug each other.

Each fin has three or four fingers on the tip, except the Amazonian manatee, which lacks these.

In relation to the cervical vertebrae, Trichechus has only six, unlike almost all other mammals that have seven. This difference in the number of vertebrae may be due to mutations in homeotic genes..

Size

Manatee weigh between 400 and 550 kilograms, although the Trichechus manatus it could weigh 1590 kilograms. In relation to the length, they measure from 2.8 to 3 meters, however, the African manatee can measure up to 4.5 meters.

The smallest of the three species is the Amazonian manatee (Trichechus inunguis), weighing about 120 to 170 kilograms and with an approximate length of 162 to 230 centimeters.

Digestive system

The manatee's digestive system is characterized by having a simple stomach, with a large cecum, in which the digestion of the hardest plant matter is carried out. As for the intestines, they are approximately 45 meters long, something unusual for an animal of its size..

Dentition

The adults of this species do not have canines or incisors, only a group of cheek teeth, which are not differentiated. Thus, in this set of teeth, premolars and molars cannot be distinguished..

On each side of the jaw it has between 6 and 8 high crown and open root teeth, for a total of 24 to 32 teeth.

The type of vegetation that forms their diet erodes the enamel of the teeth, which particularly in the manatee is quite weak. To compensate for this situation, teeth are continually replaced. Thus, when anterior molars wear out, they fall out.

The new molars emerge at the back and slowly advance to replace the others. This process occurs throughout the life of the animal.

The speed with which the teeth migrate forward will depend on how quickly the other teeth wear out. Research indicates that this rate can be 0.1 to 1 centimeter per month.

Habitat and distribution

Chris Muenzer [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)]

Members of the genus Trichechus are found throughout the subtropical and tropical Atlantic coasts and in the associated inland waters, including the hydrographic basins of the Niger and Amazon rivers.. 

Amazonian manatee

The Amazon manatee (Trichechus inunguis) lives in the Amazon River in northern South America and in related drainage areas, encompassing seasonally flooded forests.

This species lives only in fresh water and can be found from the Marajó Islands, in Brazil, to Colombia, Ecuador and Peru. Occasionally, its habitat may overlap, off the coast of Brazil, with that of the West Indian manatee.

Contrary to the other subspecies, the Amazonian manatee is never in contact with salt water, so it is the only one that lives exclusively in fresh water. It has several favorite habitats, such as lagoons connected to rivers rich in aquatic vegetation and backwater lakes..

It can carry out seasonal migrations, moving from flooded areas, in the wet season, to rivers or deep lakes, during the dry season.

African manatee

The species Trichechus senegalensis, Known as the African manatee, it lives in coastal areas and in slow-moving rivers, from Senegal to Angola. In addition, it usually extends inland, in some rivers of these regions.

Thus, it is located throughout the west coast of Africa, from the Senegal River to the Cuanza River, located in Angola. It can be found both on the Niger River, and in Koulikoro, in Mali, about 2,000 km from the coast.

The African manatee is found in Angola, Benin, Chad, Cameroon, the Republic of the Congo, Ivory Coast, the Democratic Republic of the Congo and Equatorial Guinea It also lives in Gabon, Ghana, Gambia, Guinea, Liberia, Guinea Bissau, Mali, Mauritania , Nigeria, Niger, Sierra Leone, Senegal and Togo.

This species inhabits estuaries and coastal marine regions, as well as freshwater rivers. So it can be found from brackish to sweet water, with temperatures above 18 ° C. Thus, it lives in lakes, rivers, coastal estuaries, lagoons, mangroves, reservoirs and coastal bays..

African manatees have been sighted up to 75 kilometers from the coast, where there are mangrove streams with abundant sea grasses. During the drought, the flow of the rivers varies, so it can connect with some lakes such as the Volta and the Léré. In this way, these bodies of water become shelters until the river waters return to their normal level..

Some of the river systems where manatees live are: Senegal, Gambia, Casamance, Mansôa, Buba, Cacine, Congo, Kondou, Sierra Leone, Sherbro, and Malem. These mammals swim through these rivers until they cannot advance, due to the shallow water or the presence of strong waterfalls..

West Indian manatee

As for the West Indian manatee (Trichechus manatus) is distributed in brackish areas, in coastal marine and freshwater zones, located in the subtropical and tropical southeast of the Gulf of Mexico, the United States, the Caribbean Sea and the Atlantic coast, in the southeast of South America.

Subspecies Trichechus manatus latirostris, Called the Florida manatee, it lives from Louisiana to Virginia, in the northern Gulf of Mexico area. It is also found in the southeastern United States. The other subspecies, Trichechus manatus manatus, inhabits from northern Mexico to Brazil and the Caribbean islands.

In this way, it is found in French Guiana, Bahamas, Suriname, Trinidad, Guyana, Venezuela and Panama. It is also in Colombia, Nicaragua, Costa Rica, Honduras, Belize, Guatemala, Mexico, Haiti, the Dominican Republic, Puerto Rico and Jamaica.

The West Indian manatee lives in shallow coastal areas. However, studies indicate that it has the ability to withstand changes in water salinity. Because of this, it also inhabits rivers and shallow estuaries. Thus, this species can live in brackish, sweet and saline water.

Motivated by its low metabolic rate and a thin layer of insulating fat, its habitat is limited to the subtropics and the tropics. This is why they prefer shallow and warm waters.

Frequently, the West Indian manatee migrates through the brackish water estuary to the freshwater spring. Studies indicate that Florida manatees need access to fresh water in order to regulate salts in their bodies..

Likewise, this mammal does not tolerate waters with temperatures below 15 ° C, so during the winter it seeks refuge in warm rivers, which are fed by springs..

Danger of extinction

Since the 1980s, the three species of manatees have been categorized by the IUCN as vulnerable to extinction. According to research carried out by this international organization, it is expected that, in the next 20 years, their populations will decrease by up to 30% more.

- Threats

Collision with ships

The curious nature and the slow movements, together with the great development of the coasts, bring as a consequence the collision of these animals against the boats.

These accidents can mutilate some parts of your body and even cause death. Even tears in your skin could cause serious infections that could be fatal.

Species of the genus Trichechus can hear sounds located at a high frequency. Some large boats emit low frequencies, which can confuse the manatee and lead to colliding with ships.

Research carried out on this topic indicates that when the boat has a high frequency, the animal moves away quickly.

In Florida, motorboat collisions and smashing into canal gates are the leading causes of death. Some specialists estimate that around 25 to 35 percent of manatee deaths in that North American state are caused by this reason..

Red tide

Another factor that causes manatee death is red tide, a term that refers to the proliferation of algae. Karenia brevis. This microscopic dinoflagellate produces brevetoxins that could affect the central nervous system of animals, due to their toxicity..

In 1996, this resulted in the death of 151 manatees. The algae bloom occurred from the first days of March through April, killing about 15% of the manatee population on the south coast of Florida. Other blooms, in 1982 and 2005, triggered approximately 37 and 44 deaths, respectively.

Hunting

The manatee has been hunted in a traditional way, even since pre-Hispanic times. Currently it continues to be caught in South America and Central America. The main products marketed are the skin and its meat.

Native Americans used the skin to make war shields and shoes. However, the main reason for their hunting is their meat.

Environmental conditions

The manatee is affected by low water temperatures, which could lead to thermal shock. During winter, the water can be below 20 ° C, which could cause the death of this mammal, since its body does not tolerate this temperature.

To try to warm themselves, some tend to congregate on the Florida coast, very close to the outlets of the hot waters coming from the power plants. This has strongly drawn the attention of experts, because that group of manatees no longer migrates south as they previously did..

In 2010, the Florida Fish and Wildlife Conservation Commission noted that of the 237 deaths, 42% were as a result of this cold stress syndrome..

Environmental pollution

One of the risks that increasingly affects the survival of Trichechus are oil spills that degrade their natural habitat. Likewise, said economic activity brings with it an increase in vessel traffic..

- Actions for your protection

The Society for Conservation Biology proposes that the objectives of manatee conservation plans should contemplate the education of the population, in addition to protectionist policies and efforts..

Although this animal is under legal protection in the countries where it lives, its population continues to decline. This is because the reproductive rate is much lower than the losses it suffers from the various threats that afflict it..

Members of this genus are included in Appendix I of CITES, so their international trade is prohibited, with the exception that this is not for commercial purposes..

Taxonomy and subspecies

Animal Kingdom.

Subkingdom: Bilateria.

Phylum: Chordate.

Subfilum: Vertebrate.

Superclass: Tetrapoda.

Class: Mammal.

Subclass: Theria.

Infraclass: Eutheria.

Order: Sirenia.

Family: Trichechidae.

Genus: Trichechus.

Species:

Trichechus inunguis.

Trichechus senegalensis.

Trichechus manatus.

Reproduction

The female manatee reaches sexual maturity at three years of age, but can reproduce successfully between seven and nine years. However, the male is apt to conceive much later, around 9 or 10 years..

Generally, mating can occur year-round, although the highest reproductive peaks may occur in the spring and the lowest during the winter..

A female usually mates with several males. They will fight each other by pushing each other, so that the victor has the opportunity to join the female. Likewise, these form mating herds around the female in heat..

The gestation period lasts between 12 and 14 months, normally one calf is born, although occasionally two may be born..

The calf weighs between 27 and 32 kilograms and can be 1.2 to 1.4 meters long. The family is made up of the mother and her young, the male does not contribute to the care of this.

The newborn is born with molars, which allows him to consume seagrass when he is three weeks old. However, still at that age he is breastfed by his mother, whom he accompanies for up to two years.

Feeding

The manatee is a herbivore with a voracious appetite, spending almost a quarter of its time feeding. The amount of food you eat will depend on the size of your body. Thus, you could consume between 4 and 10% of your body weight daily.

Among the species it consumes there is a diversity of aquatic macrophytes. In relation to those that live in fresh waters, there are water lettuces, water lilies, grasses, alligator beds, hydrilla, musk grass, mangrove leaves and floating hyacinth..

As for the plants that live in salty waters are algae, sea grasses, turtle grass, sea clover and manatee grass. When the water level is high, it can eat grasses and leaves, as well as palm fruits that fall into the water..

Also, it could eat clams, fish, and mollusks. This is probably associated with the need to meet your mineral requirements. However, some research indicates that the African manatee is the only siren that likely intentionally includes animals in its diet..

Behaviour

The manatee usually swim in pairs or alone. When it forms groups, it is usually a mating herd or simply a group that is sharing a warm area with an abundance of food..

Specialists have studied the behaviors of these mammals and claim that they use various vocalization patterns to communicate. These can vary with sex and age, indicating a vocal individuality among manatees. Thus, when a breeding pair recognizes each other, vocalizations increase.

Although calls occur frequently between the mother and her calf, it is also part of social interactions. In the event that the environment becomes noisy, the manatee increases the vocal effort to emit the sounds.

According to anatomical and acoustic tests, the vocal folds could be responsible for the mechanism of sound production.

To get around, he can swim at 5 to 8 kilometers per hour, although he could make short and quick movements, reaching up to 30 kilometers per hour. Its fins are used to travel the seabed and to dig in it, when it finds plants or roots that it can consume..

References

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