Trinidad and Tobago are continental islands with a geologically very recent history of direct land bridge connection to South America. As a result, unlike most of the Caribbean Islands, Trinidad and Tobago supports a primarily South American flora and fauna and has greater diversity of plant and animal species than the Antilles. However, rates of endemism are lower than in the rest of the Caribbean because there has been less time for genetic isolation from mainland populations because of the history of land bridge connections and hence fewer opportunities for speciation, and so a greater proportion of the species in Trinidad and Tobago are also found on the South American mainland. Trinidad is nearer to mainland South America and has been directly connected to the mainland via land bridges more often and for longer periods than Tobago. This, as well as Trinidad's larger size and more varied topography and hydrology compared to that of Tobago allow greater species and ecosystem diversity on the former compared to that on the later of the islands.
Plant communities
The standard description of plant communities follows John Beard's work (Beard, 1946). He classified natural vegetation in a hierarchical fashion on the basis of the physiognomy of the dominant trees.
Seasonal formations
Evergreen seasonal forest
Semi-deciduous seasonal forest
Deciduous seasonal forest
Dry evergreen formations
Littoral woodland
Montane formations
Lower montane forest
Montane forest
Elfin woodland
Edaphic formations
Mangrove forest
Palm swamp
Seasonal swamp forest
Seasonal swamp savanna
Herbaceous swamp
Terrestrial animal communities
Mammals
Trinidad and Tobago is home to about 99 species of terrestrial mammals. About 65 of the mammalian species in the islands are bats (including cave roosting, tree and cavity roosting bats and even foliage-tent-making bats; all with widely differing diets from nectar and fruit, to insects, small vertebrates such as fish, frogs, small birds and rodents and even those that consume vertebrate blood). The next most diverse group of mammals in the islands are the rodents. The largest of these rodents are the lowland paca, the Brazilian porcupine, and the red-rumped agouti (of these, only the agouti remains extant on Tobago). One squirrel (the red-tailed squirrel) and several native rats and mice are also part of the rodent fauna. A few species of opossums including the common opossum may be found on both islands. Two anteaters, the southern tamandua and the silky anteater are found in Trinidad (but not in Tobago). The nine-banded armadillo can still be found on both islands. Native mammals of the order Carnivora include the ocelot, the tayra, the Neotropical river otter and the crab-eating raccoon (all four being found on Trinidad, with only the raccoon still extant on Tobago). The small Indian mongoose was introduced to Trinidad (but not to Tobago) during the later part of the 19th century and is now naturalized. The two native hoofed-mammals still found in Trinidad include the red brocket deer and the collared peccary (in Tobago, the deer is thought to be extirpated and the peccary is now fairly rare). The Guyanan red howler monkey and the white-fronted capuchin are Trinidad's two native non-human primate species. The tufted capuchin monkey was introduced to the northwestern peninsula of Trinidad during World War II and is now naturalized there. No monkeys remain extant on Tobago. For comments on native aquatic mammals (namely manatees) and native marine mammals (whales and dolphins), see the appropriate sections below.
Birds
472 species of birds have been recorded in Trinidad and Tobago (and the list of recorded species seems be still slowly increasing from year to year). There are few places in the world where so many birds can be seen in such a small area (with probably one of the highest bird species to area ratios of any country). Many of the species are very rare or are of particular interest. They range from the many species of hummingbirds to the primitive cave-dwelling oilbird (that uses sonar to fly in the dark) to the spectacularly beautiful scarlet ibis. The islands are within a few miles of Venezuela, and the species are therefore typical of tropical South America. However, the variety (although quite exceptional for such a small geographic area) is somewhat impoverished compared to the mainland, as would be expected with small islands.
The resident breeding birds are augmented in the northern winter by migrants from North America.