The Amazonian manatee (Trichechus inunguis), commonly referred to as cowfish in Brazil, is a species of manatee that lives in the Amazon Basin in Brazil, Peru, Colombia and Ecuador. It is the smallest of the three extant species of manatee.

Taxonomy

The specific name, inunguis is Latin for "nailless". The genus name Trichechus, comes from Latin meaning "hair", referencing the whiskers around the manatee's mouth.

Amazonian manatees are large, cylindrically shaped mammals, with forelimbs modified into flippers, no free hind-limbs, and the rear of the body in the form of a flat, rounded, horizontal paddle. The flexible flippers are used for aiding motion over the bottom, scratching, touching, and even embracing other manatees, and moving food into and cleaning the mouth.

The Amazonian manatee lacks nails on its flippers, setting it apart from other manatees.

Behavior and biology

The Amazonian manatee is the only sirenian that lives exclusively in freshwater habitat. The species relies on changes in the peripheral circulation for its primary mechanism for thermoregulation by using sphincters to deflect blood flow from areas of the body in close contact with water. They also rely on subcutaneous fat to reduce heat loss.

Manatees have nostrils, not blowholes like cetaceans, which close when underwater to keep water out and open when above water to breathe. Although manatees can remain under water for extended periods, surfacing for air about every five minutes is common. The longest documented submergence of an Amazonian manatee in captivity is 14 minutes. Only its nostrils protrude from the surface of the water while it searches river and lake bottoms for vegetation.

Diet

The manatees themselves feed on a variety of aquatic macrophytes, including aroids (especially Pistia, aka "water lettuce"), grasses, bladderworts, hornworts, water lilies, and particularly, water hyacinths. They are also known to eat palm fruits that fall into the water.

During the July–August dry season when water levels begin to fall, some populations become restricted to the deep parts of large lakes, where they often remain until the end of the dry season in March. After the calf is born, it will begin to eat while staying with its mother for 12 – 18 months.

Wild individuals have a lifespan of about 30 years.

Population and distribution

As of 1977 the population count of the Amazonian manatee was estimated to be around 10,000.

Amazonian manatees occur through most of the Amazon River drainage, from the headwaters, in Colombia, Ecuador and Peru to the mouth of the Amazon (close to the Marajó Island) in Brazil over an estimated seven million square kilometers.

The Amazonian manatee is completely aquatic and never leaves the water. They are mainly solitary but sometimes they will gather in small groups consisting of up to eight individuals.

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Further reading

  • ARKive - images and movies of the Amazonian manatee (Trichechus inunguis)
  • Amazonian Manatee article at sirenian.org
  • Multiple new species of large, living mammals (part III) - Tetrapod zoology. Accessed March 16, 2008.