American Oceans

Amazonian Manatee

The Amazonian manatee, also known as Trichechus inunguis, is a unique aquatic mammal found exclusively in the freshwater habitats of the Amazon River and its tributaries in South America.

an amazonian manatee swimming underwater

This species of manatee is the smallest of the three extant species of manatee and is a member of the Sirenia order. The Amazonian manatee is a gentle and docile creature that can live up to 60 years in the wild.

The Amazon River Basin is home to one of the most diverse and unique ecosystems in the world.

The Amazonian manatee plays a crucial role in this ecosystem, as it is a primary food source for predators such as jaguars, anacondas, and caimans.

Unfortunately, due to habitat loss and hunting, the population of Amazonian manatees has declined significantly over the years.

As a result, the Amazonian manatee is listed as a vulnerable species by the International Union for Conservation of Nature (IUCN).


Geography and Habitat

The Amazonian manatee (Trichechus inunguis) is found in the Amazon River and associated drainage areas, including seasonally inundated forests.

an amazonian manatee interacting with a boat on the water

This species lives only in freshwater and can be found far inland through Brazil to Ecuador, Peru, and Colombia.

In Brazil, the Amazonian manatee can be found in the Amazon River and its tributaries, including the Rio Negro.

In Peru, it is found in the Amazon River and its tributaries, including the Ucayali and Marañón rivers.

In Colombia, the Amazonian manatee is found in the Amazon River and its tributaries, including the Caquetá and Putumayo rivers.

Habitat

The Amazonian manatee is a freshwater species and is found in a variety of freshwater habitats, including rivers, streams, and blackwater lakes.

They prefer slow-moving or still waters and are often found in areas with dense vegetation.

Amazonian manatees are also known to inhabit flooded forests during the rainy season. These manatees are both nocturnal and diurnal and live their lives almost entirely underwater.

Amazonian manatees are gregarious animals and used to occur in big herds. Due to severe overhunting, however, groups seen today number only 4 to 8 individuals.

Despite their size, Amazonian manatees are excellent swimmers and can swim up to 8 km/h (5 mph) for short distances.

They are also capable of diving to depths of up to 10 meters (33 feet) for several minutes at a time.


Biology and Behavior

The Amazonian manatee is a large aquatic mammal that can weigh up to 590 kg (1,300 lb) and grow up to 2.8 m (9.2 ft) in length. It has a flexible flipper that helps it move through the water with ease.

an amazonian manatee claf taking a breath of air from the surface

The manatee has an upper lip that is prehensile and can grasp vegetation. Its skin has a bristly surface that helps it sense its environment.

The coloration of the Amazonian manatee is brown or gray, which helps it blend in with the murky waters of the Amazon basin.

The Amazonian manatee has cheek teeth that are continuously replaced throughout its life. This adaptation allows it to feed on tough vegetation, which is its primary source of food.

Behavior

The Amazonian manatee is a social animal that lives in small groups of 4 to 8 individuals. It is both diurnal and nocturnal, spending most of its time underwater.

The manatee is a slow-moving animal that spends much of its time grazing on aquatic vegetation.

It can submerge for up to 15 minutes at a time before surfacing to breathe.

The Amazonian manatee is known to vocalize, producing a variety of sounds that are used for communication.

It is also known to be a curious animal, often approaching boats and people in the water.

However, the manatee is threatened by habitat loss and overhunting, which has led to a decline in its population.


Diet and Feeding Habits

As a herbivore, the Amazonian manatee feeds on a variety of aquatic vegetation, such as grasses, water hyacinths, water lettuce (pisitia), and floating palm fruits. They have also been known to crop overhanging branches and consume acorns.

an amazonian manatee eating vegetation in a river

Manatees must eat large amounts of bulky, low-energy food to satisfy their dietary requirements. Captive adults daily consume from 9 – 15 kilograms (20 – 33 pounds) of leafy vegetables.

Method of feeding is also an interesting aspect of the Amazonian manatee’s diet. They feed off the bottom, in the water column, and at the surface.

They use their front flippers and large, flexible lips to manipulate vegetation.

They have even been observed hauling themselves partially out of the water to eat bank vegetation, including the leaves of mangrove trees.


Reproduction and Life Cycle

The Amazonian manatee is a seasonal breeder with a gestational period of 12-14 months and a prolonged calving period.

a baby amazonian manatee swimming underwater

Most births take place between December and July, with about 63% between February and May, during a time of rising river levels in their native region.

Breeding

When a female Amazonian manatee goes into estrus, she is pursued by numerous male manatees throughout the cycle, perhaps for a duration of up to three weeks.

During that time, the female can mate with one or more males in what is known as an estrous or mating herd.

The male Amazonian manatee produces a sperm plug that temporarily blocks the female’s genital tract, which may prevent other males from fertilizing her eggs.

Gestation

The gestation period of the Amazonian manatee is one of the longest among mammals. The female carries the calf for 12-14 months, and the calf is born underwater.

The newborn calf is about 1 meter long and weighs around 20 kg. The calf is able to swim and breathe on its own immediately after birth.

Calf

The Amazonian manatee calf is dependent on its mother’s milk for the first year of its life. The mother produces milk with a high fat content to help the calf grow quickly.

The calf stays close to its mother for the first few months of its life, and the mother provides protection from predators.

The calf will start to eat aquatic plants at around three months old, but it will continue to nurse for up to 18 months.

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