Trichechus manatus (West Indian Manatee/ Sea Cow)
The manatee is classified as an Environmentally Sensitive Species in Trinidad and Tobago.
2007 IUCN Red List Category – Vulnerable

SCIENTIFIC CLASSIFICATION

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Sirenia
Family: Trichechidae
Genus: Trichechus
Species: T. manatus
Gill (1872)

DESCRIPTION

Identification: West Indian manatees are large, gray aquatic mammals with bodies that taper to a flat, paddle-shaped tail. They have two forelimbs, called flippers, with three to four nails. Their head and face are wrinkled with whiskers on the snout. The manatee's closest land relatives are the elephant and the hyrax, a small, gopher-sized mammal. Manatees are believed to have evolved from a wading, plant-eating animal. The West Indian manatee is related to the West African manatee, the Amazonian manatee, the dugong, and to the Steller's sea cow, which was hunted to extinction in 1768. The manatee can grow up to four metres (13 feet) long and weighs between 362-544 kilograms (800-1,200 pounds).

Manatees are gentle and slow-moving. Most of their time is spent eating, resting, and in travel. Manatees feed primarily on sea grasses and sometimes, on small invertebrates. They can consume 10-15% of their body weight daily in vegetation.

The West Indian sea cow has evolved in areas with no natural predators and as a result the members of this species have had no need to develop complex behaviours for predator avoidance. It is believed they can live 60 years or more.

The Florida manatee (Trichechus manatus latirostris) is a subspecies of the West Indian manatee. The other subspecies of the West Indian manatee is sometimes referred to as a Caribbean/Antillean manatee (Trichechus manatus manatus).

Behaviour: They graze for food along water bottoms and on the surface. They may rest submerged at the bottom or just below the surface, coming up to breathe on the average of every three to five minutes. When manatees are using a great deal of energy, they may surface to breathe as often as every 30 seconds. When resting, manatees have been known to stay submerged for up to 20 minutes.

The areas inhabited by this species have fairly constant temperatures year-round and an abundant food source, and without the need for group foraging techniques or group defence, this species is largely solitary, occasionally forming loose aggregations.

Manatees are not territorial and do not observe any social hierarchy. Most groups are temporary associations, without regard to sex or age. One exception is herds of juvenile males, which are temporary groups that arise from the exclusion of such individuals from reproductive activities. In addition temporary mating herds develop when a female is in oestrus (estrus).

Manatees use their tail to propel themselves forward and are surprisingly agile in the water. They are capable of complex manoeuvring including somersaults, rolls, and swimming upside-down. They are active day and night, resting for several hours at a time near the surface of the water or at the bottom. While resting on the bottom, they rise to the surface to breathe every few minutes.

Manatees use various forms of communication in the water. Individuals rub themselves against hard surfaces, possibly secreting a scent to convey information about the reproductive state of the resident females. Manatees also have an acute ability to hear and squeals are often used to keep contact between a mother and calf. Vision seems to be the preferred method of navigation.

Reproduction: The reproductive rate for manatees is slow. Young females lack the skills necessary to raise calves and are less successful breeders. Most females breed successfully between the ages of 7 and 9. Female manatees are not sexually mature until about 5 years of age, and males are mature at approximately 9 years of age. The only stable group within the manatee population is that of a mother and her calf. Other than that, at breeding time, males will join in groups and follow the receptive female.

Gestation period lasts from 12 to 14 months. Normally, one calf is born, although on rare occasions two have been recorded, every two to five years. Mothers nurse their young for 1 to 2 years, so a calf may remain dependent on its mother during that time even though the young are born with molars and premolars, which allow them to consume sea grass within the first 3 weeks of birth. The family unit consists of mother and calf, which remain together for up to 2 years. Males usually contribute no parental care to the calf.

RANGE AND POPULATION

Population estimate: 25 - 30 (UNEP/CEP 1995)
Very little information is available on the current manatee population.
Population trend: Decreasing
Country endemic: No
Range: Manatees inhabit warm waters of the Caribbean from Florida to Brazil where they live in coastal waters, freshwater inlets, and river mouths. During summer, these large mammals have even been found as far north as Rhode Island.

Although their range is quite large, manatees today exist only in a few small, isolated populations. They once were widespread in rivers and along coasts in their range, but they were hunted extensively in the 18th and 19th centuries. Coastal development has further reduced their populations.

The destruction of the swampland habitat for development and agricultural uses has annihilated local populations. Now, less than a hundred manatees live in the Nariva Swamp, a protected area.

THREATS

Most manatee mortalities are human-related and usually occur from collisions with watercraft. Other causes of human-related manatee mortalities include ingestion of fish hooks, litter and monofilament line; and entanglement in crab trap lines. Ultimately, however, loss of habitat is the most serious threat facing manatees today.

CONSERVATION MEASURES

Current measures: As identified on the CITES (Convention on International Trade in Endangered Species) Appendix I listing, which has been updated as recently as February 2008 – the Pipile pipile has been legally protected since 1963. There were conservation and education campaigns in the 1980s, but more recent initiatives in the late 1990s appeared to start a changing of attitudes. Much of the present range is within forest reserves and state forests, but the laws protecting both species and areas are generally not enforced. The Matura National Park is protecting a large area since 2006 when the necessary legislation was passed. Species-specific ecotourism is having a positive effect in the northern area of Grande Riviere, providing financial support for local communities and developing a sense of collective responsibility.
Proposed measures: There are plans to use radio-telemetry to learn more about the species’ biology. There are also plans to survey areas of historic occurrence to determine its status in these areas as well as monitor the population in areas of known occupancy. Ecological requirements and breeding biology are also to be determined. The protection of current forest reserves are to be more stringently enforced. Further education/public awareness campaigns are also to be developed in order to ensure the success of site protection.
References
Shoshani, Jeheskel (November 16, 2005). in Wilson, D. E., and Reeder, D. M. (eds): Mammal Species of the World, 3rd edition, Johns Hopkins University Press, 93. ISBN 0-801-88221-4.
Deutsch, C.J., Self-Sullivan C. & Mignucci-Giannoni, A. (2007). Trichechus manatus. 2007 IUCN Red List of Threatened Species. IUCN 2007. Retrieved on 2007-09-13. Listed as Vulnerable (VU C1 v3.1)
Domning and Hayek (1986) "Interspecific and intraspecific morphological variation in manatees (Sirenia: Trichechus)". Marine Mammal Science 2 (2): 87-144.
Hatt (1934) "The American Museum Congo Expedition manatee and other recent manatees". Bulletin of the American Museum of Natural History 66: 533-566.
Garcia-Rodriguez, B W. Bowen, D. Domning, A. A. Mignucci-Giannoni, M. Marmontel, R. A. Montoya-Ospina, B. Moreales-Vela, M. Rudin, R. K. Bonde, and P. M. McGuire (1998). "Phylogeography of the West Indian manatee (Trichechusmanatus): How many populations and how many taxa?". Molecular Ecology 7: 1137-1149.
Vianna et al. (2006) "Phylogeography, phylogeny and hybridization in trichechid sirenians: implications for manatee conservation". Molecular Ecology 15: 433-47.
Manatees May Lose Status St. Petersburg Times, 2007-04-10,  Retrieved on 10 May 2007
Deutsch, C.J., Self-Sullivan, C. & Mignucci-Giannoni, A. (2007) Trichechus manatus ssp. latirostris. 2007 IUCN Red List of Threatened Species. IUCN 2007. Retrieved on 2007-12-03.
(FPL 1989, Nowak 1999, Rathbun 1990)