Animal Info - Amazonian Manatee

(Other Names: Amazon Manatee, Lamantin d'Amérique du Sud, Lamantin de l'Amazone, Lamantino Amazónico, Lamantine, Manatí Amazónico, Peixe-boi, Peixe-Boi-da-Amazônia, South American Manatee, Vaca Marina Amazónica)

Trichechus inunguis

Status: Vulnerable

1. Profile (Picture)
2. Tidbits
3. Status and Trends (IUCN Status, Countries Where Currently Found, Taxonomy, Population Estimates, History of Distribution, Threats and Reasons for Decline)
4. Data on Biology and Ecology (Size, Habitat, Gestation Period, Birth Season, Birth Rate, Maximum Age, Diet, Behavior, Social Organization)
5. References

Profile

Pictures: Amazonian Manatee #1 (5 Kb JPEG); Amazonian Manatee #2 (19 Kb JPEG)

Manatees are large, cylindrically shaped mammals, with forelimbs modified into flippers, no free hindlimbs, 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 manatee's upper lip is modified into a large bristly surface, which is deeply divided. It can move each side of the lips independently while feeding. The general coloration is gray, and most Amazonian manatees have a distinct white or bright pink patch on the breast. The largest recorded Amazonian was a male with a length of 2.8 m (9.2'). In contrast, the other two manatee species both range in length from 2.5 m (8.2') up to more than 4.5 m (14.8').

The Amazonian manatee occurs exclusively in fresh water. It prefers blackwater lakes, oxbows, and lagoons with deep connections to large rivers and abundant aquatic vegetation. The Amazonian manatee is a herbivore that feeds on aquatic vegetation near lake edges, such as aquatic grasses, and floating vegetation such as water lilies. The Amazonian manatee is both diurnal and nocturnal. It is entirely aquatic and never leaves the water. Amazonian manatees do most of their feeding during the wet season, when they eat new vegetation in seasonally flooded backwaters. During the dry season (September - March), when they congregate in the main river channels or in deep parts of larger lakes, they may fast for weeks or months for lack of available food plants. There have been reports of larger aggregations of manatees in the middle reaches of the Amazon, but the largest groups of manatees observed currently generally include only 4 - 8 animals. Most manatees observed are either solitary or a female with her young.

The Amazonian manatee ranges throughout the Amazon River Basin of northern South America. Its range sometimes has been said to include the Orinoco River Basin, but such reports apparently are based on misidentification of the American manatee in the early 19^th century. The Amazonian manatee has long been hunted by subsistence and commercial hunters. Its populations continue to decline, mainly due to hunting. Other threats include accidental drowning in commercial fishing nets and degradation of food supplies by soil erosion resulting from deforestation.

Tidbits

*** "The manatee, or lamantine, is a very strange-looking creature, appearing like a curious mixture of several dissimilar animals, the seal and the hippopotamus being predominant." (Wood 1860)

*** The manatee does not have incisors or canine teeth, only cheek teeth (molars). Molars designed to crush vegetation form continuously at the back of the jaw and move forward as older ones wear down. The older ones eventually fall out, while new ones come in at the rear of the jaw to replace them.

*** The three species of manatees, and the closely related dugong, are unique in that they are the only plant-eating marine mammals in modern times.

Status and Trends

IUCN Status:

1960's - 1970's: Endangered
1980's - 1994: Vulnerable
1996 - 2004: Vulnerable (Criteria: A1cd) (IUCN 2004)

Countries Where the Amazonian Manatee Is Currently Found:

2004: Occurs in Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela. (IUCN 2004)

Taxonomy:

There are three species of manatees: the Amazonian manatee (Trichechus inunguis), the American manatee (Trichechus manatus), and the West African manatee (Trichechus senegalensis). The American manatee and the West African manatee are all gray and do not have the distinct white or bright pink patch on the breast characteristic of most Amazonian manatees. The Amazonian manatee is smaller and more slender than both of the other two manatee species.

Population Estimates:

[Note: Figures given are for wild populations only.]

WORLD
- 1977: A minimum population of 10,000 (Husar 1977)

History of Distribution:

The Amazonian manatee ranges throughout the Amazon River Basin of northern South America. Its range sometimes has been said to include the Orinoco River Basin, but such reports apparently are based on misidentification of the American manatee in the early 19^th century. It is also unlikely that it reaches the waters that connect the Orinoco and Amazon basins. It occurs at the mouth of the Amazon on the Atlantic coast. (Nowak 1999)

The Amazonian manatee has long been hunted by the Amazonian Indians, and during the 1930's and 1940's, exploitation was extensive (Husar 1977). Nonetheless, in 1942, it was reported to be found in good numbers in the Amazon River and its larger tributaries (Allen 1942). During the second half of the 20th century, it continued to decline due to hunting (IUCN 1966, Curry-Lindahl 1972, Emmons & Feer 1997).

Distribution Map for Amazonian Manatee (23 Kb JPEG)
Distribution Map for all Sirenia (Dugong and Manatee Species) (22 Kb GIF) (Wildl. Trust)

Threats and Reasons for Decline:

The Amazonian manatee has been heavily hunted by subsistence and commercial hunters. It has been sought for meat, oil and fat, and at one time for its hide, which was in demand for use as water hoses and machine belts. Other threats include accidental drowning in commercial fishing nets and degradation of food supplies by soil erosion resulting from deforestation. (IUCN 1966, Husar 1977, Nowak 1999)

Data on Biology and Ecology

Size:

The largest recorded specimen was a male with a length of 2.8 m (9.2'). In contrast, the other two manatee species, the American manatee and the West African manatee, both range in length from 2.5 m (8.2') up to more than 4.5 m (14.8').

Habitat:

The Amazonian manatee occurs exclusively in fresh water. It prefers blackwater lakes (pH 4.5 - 6.5), oxbows, and lagoons, and it has been maintained successfully in waters with temperatures of 22 - 30 deg C (72 - 86 deg F). Its key requirements in the wild seem to be large blackwater lakes or lagoons with deep connections to large rivers and abundant aquatic vegetation. (Nowak 1999)

Gestation Period:

Approximately a year.

Birth Season:

Breeding has been reported to occur throughout the year in some areas. However, it has been reported that births occur mainly in January in one part of Amazonian Ecuador and in June in another. Evidence also indicates that in the central Amazon Basin, breeding is seasonal, with nearly all births taking place from December to July (mainly from February - May, the period of rising river levels). (Nowak 1999)

Birth Rate:

One is the usual number born. The calving interval may be 2 years.

Maximum Age:

Two individuals lived 12.5 years (captivity).

Diet:

The Amazonian manatee is a herbivore that feeds on aquatic vegetation near lake edges, such as aquatic grasses, and floating vegetation such as water lilies. Captive adults daily consume from 9 - 15 kg (20 - 33 lb) of leafy vegetables.

Behavior:

The Amazonian manatee is both diurnal and nocturnal. It is entirely aquatic and never leaves the water. It lives entirely under the water; only its nostrils break the surface when it rises to breathe. It usually surfaces several times per minute to breathe, although the longest recorded submergence is 14 minutes.

Amazonian manatees do most of their feeding during the wet season, when they eat new vegetation in seasonally flooded backwaters. Manatee populations of the central Amazon Basin make an annual movement in July - August, when water levels begin to fall. Some return to the main river channels, where, when the rivers shrink in the dry season (September - March), they may fast for weeks for lack of available food plants. Others become restricted to deep parts of larger lakes during the dry season, where they do not have obvious food sources until water levels rise 1 - 2 m (3 - 6'). Available evidence suggests that the latter populations fast for nearly 7 months, though they may take some vegetation. The manatee's large fat reserves and low metabolic rate, only about 1/3 of the usual rate for most mammals, allow it to survive at this time. (Emmons & Feer 1997, Nowak 1999)

Female manatees carry calves on their backs or clasped to their side.

One Amazonian manatee was radio-tracked for several days. Its rate of movement was 2.6 km/day (1.6 mi/day) (Eisenberg & Redford 1999).

Social Organization:

In a study conducted in the early 1980's at Lago Amana, 500 -1000 manatees were observed congregating during the dry season. There have been other reports of large aggregations of manatees in the middle reaches of the Amazon, but such gatherings appear rare today. Currently, groups of 4 - 8 manatees can be seen in feeding areas, but most manatees observed are either solitary or a female with her young. The mother-calf bond seems to be long-lasting. (Husar 1977. Emmons & Feer 1997, Nowak 1999)

References

Allen 1942, Curry-Lindahl 1972, Eisenberg 1989, Eisenberg & Redford 1999, Emmons & Feer 1997, Husar 1977, IUCN 1966, IUCN 1994, IUCN 1996, IUCN 2000, IUCN 2003a, IUCN 2004, Nowak 1999, Wildl. Trust, Wood 1860

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Last modified: January 9, 2005;