The New Neotropical Companion

Swamps

A swamp is generally an area of woody vegetation that

is inundated by standing water for a significant part

of the year. Swamps are typically much lower in tree

species richness than less wet sites, and some swamps

are made up mostly of a single species. Many swamp

tree species have stilt root systems, and buttressing of

the trunk is extremely common as well (chapter 3).

Along the coast, where saltwater incursion is normal,

swamps are composed of various combinations of

mangrove species (mangroves are discussed later in

this chapter). Throughout interior Amazonia the most

characteristic swamp forests are composed of palms,

notably the Moriche Palm (Mauritia flexuosa; plate 12-

12). Commonly called buriti in Brazil, the Moriche is

one of the most distinctive, abundant, and widespread

Neotropical palms, growing in swamps and along wet

areas, often forming pure stands. A Moriche Palm

swamp forest is termed an aguajale. Moriche Palms are

tall and slender, their fronds appearing as spike- tipped

fans on elongate stalks that radiate from a common base

atop the trunk.

Flooded Forests

Floodplain forests within the Amazon Basin cover an

area of approximately 150,000 km^2 (approx. 58,000

mi^2 ). Overall, floodplain forest comprises only about

4% of the total Amazon Basin, the remaining forest all

being terra firme. Floodplain forests are so named, of

course, because they are inundated by the annual flood

cycle. Depending upon location, floodplain forests may

be inundated for anywhere from two to 10 months out

of the year.

Flooded forests have lower tree species richness

than terra firme forests. A few are largely dominated

by a single species. Thus far it is unclear how physical

conditions influence the relative species richness of

trees occupying flooded forests. Perhaps dry- season

effects and wet- season effects combine to affect

survival of swamp-inhabiting species. The ability of

root systems to grow deeply in flooded forests may be

essential in the trees’ surviving drought stress during

dry season as well as inundation in wet season.

Flooded forests may border whitewater, clearwater,

or blackwater rivers (chapter 6). Whitewater flooded

forests, where soil nutrients are abundant, are typically

higher in stature and biomass (and probably species

richness) than clearwater rivers. Flooded forests of

blackwater rivers are typically low in stature, and

species richness tends to be a bit lower and to vary less

from site to site as compared with whitewater rivers;

many species of these forests are important fruit and

seed consumers as well as seed dispersers. There is no

simple explanation for how plant species that may be

flooded for most of the year are able to survive such

conditions. Their roots lack access to oxygen for much

of the year, and yet there are no obvious physiological

or anatomical adaptations that explain how they endure

such immersion. Certain monkey species are restricted

to floodplain forest, as are many species of birds and

arthropods. Some plant species are unique to flooded

forests, though many have closely related species in dry

forests, suggesting a recent speciation between dry and

floodplain species. Perhaps most important, many fish

species are active consumers of fallen fruit during the

wet season when the forests are flooded, and in some

cases are important seed dispersers. One in particular,

the Tambaqui (Colossoma macropomum), is considered

uniquely important in this regard (chapter 10).

Floodplain forest is not an absolute term. Some

forested areas are located immediately adjacent to the

river and flood frequently, while areas further from the

river may be flooded infrequently.

Observing Wildlife along the Rivers

and Tributaries

Two Dolphins and Two Manatees

There are two well- known species of freshwater

dolphins found in the Amazon and its major tributaries,

and both are relatively common and frequently

observed. The largest and most widespread is the Pink

River Dolphin, or Boto (Inia geoffrensis; plate 12- 13).

In Spanish- speaking areas it is usually called bufeo or

tonina, while boto is its name in Portuguese- speaking

Brazil. Pink River Dolphins hunt for fish and other

aquatic animals (turtles, crabs) in muddy waters of the

Amazon and Orinoco Basins, and they forage among

the trees of flooded forests. They are pale in color,

often distinctly pinkish, and range in length from

about 2 to 2.5 m (6.5– 8.2 ft) and have a long, slender

snout, bulbous head, and a modest dorsal fin. Botos

are usually in small groups of two to four animals,

often at the mouth of a tributary or stream. Unlike the

majority of dolphins, Botos have a flexible neck, put

chapter 12 cruising the rivers to the sea 213