Riverine Habitats

• Rivers strongly influence the surrounding landscape by seasonal flooding (up to 15m is not uncommon), supplying a constant water during the dry season, altering the microclimate (e.g. gallery forests), and providing a variety of habitats in the landscape (e.g. swamps, marshes, streams, oxbow lakes, and river islands)

Riverine Habitats

Riverine Habitats

• The Orinoco River is long (2,560km), flowing northeast from the Rio Guaviare in eastern Columbia, bisecting Venezuela before exiting to the Atlantic Ocean

• Although the Orinoco Basin is large, it is still 1/6 the Amazon

• It largely drains the Guianan Shield

Riverine Habitats

Riverine Habitats

• The Orinoco is largely a seasonal river (15m variation not uncommon with flow decreasing to 1/25 of the highest flow)

• It bisects two distinct geologic areas• The right (S) is Precambrian from the

Guianan Sheild (old) and the left (N) bank is geologically young, forming from sediments from the Andes

Riverine Habitats

• These difference extend into the tributaries with N being more stable, constrained by bedrock and filled with rapids and waterfalls

• Te S tributaries are unstable, with shifting channels formed from alluvial deposits

Riverine Habitats

• The Amazon River starts in central Peru at the base of the Andes and drains the Maranon, Ucayali, and Tigre (which themselves are conglomerates of several smaller rivers)

• In Brazil, east of Manuas is Solimões

Riverine HabitatsGee-Whiz Facts

• Once outside the Andes, it has remarkably little drop (1.5cm/km) through the remaining 6,696km

• Although Nile is slightly longer, the Amazon carries a full 16% of the world’s river water (the delta is 320 km wide) and discharges 4.5 trillion gallons/day (or 7.1 M cubic feet per second)

• 4.4x the Congo (2nd highest in the world)

Riverine Habitats Gee-Whiz Facts

• The muddy water can be seen as far as 100km out to see (and can be tracked to Africa by NASA’s ‘color scanner’

Riverine Habitats Gee-Whiz Facts

• The river itself is 10km wide as far as 1,600km up river and large ships can migrate 3,700km (reaching Iquitos)

• Two tributaries, the Negro and Madeira rank as the 5th and 6th largest rivers in the world themselves!

• The MS ranks 10th and has 1/12th the annual discharge of the Amazon

Riverine Habitats

• In relatively recent geologic history (say 15MYA), the Amazon flowed eastward

• Why did it shift?• Many tree species and such were

dispersed (involuntarily) eastward

Riverine HabitatsAmazon Flood Cycle

• You can stand on banks of the Amazon during the rainy season and watch the water drop 1m/day. Why?

• The drainage is so large, it becomes relatively complex in that in some parts it is dry and others very wet

• E.g. rainy season in S. Amazonia O-A, in Manuas N-May, N basin A-June

Riverine HabitatsAmazon Flood Cycle

• Consequently, you can have flooding on one side of the Amazon as the water is low on the other

• Overall the pulses are relatively constant (as in discharge), although the source of said water is variable

• The relatively flat Amazon results in large sediment build up on the banks

Riverine HabitatsAmazon Flood Cycle

• When floods break through these levees, large lakes and swamps form (approximately 100,000 km2 in Amazon)

• Floods can bring water deep and wide• Water can be 7-15m deep and

penetrate 20km into the floodplain• Is this good?

Riverine Habitats

• The river system is dynamic and creates many riverine habitats

Riverine Habitats

• Open Rivers• Relatively little wildlife obvious

Riverine Habitats

• Riverine and stream edge

• For wildlife, it is better to get into some of the smaller tributaries

• Also a unique habitat for plant species

Riverine Habitats

• Riverine and stream edge• For wildlife, it is better to get into

some of the smaller tributaries• Also a unique habitat for plant

species

Riverine Habitats

• Beaches and Sandbars• There is a tremendous amount of

sediment washed from the Andes and deposited along the river edge or as sandbars

Riverine Habitats

• Many shorebirds take advantage of this habitat

Riverine Habitats

• Sandbar Scrub• Good soil (coming

from the Andes) does not stay uninhabited very long

Riverine Habitats

• River Islands• there are places in the Amazon

islands are so dense you cannot see across

• Once the vegetation on sandbars stabilizes, they can easily grow

• These are very popular with human inhabitants…Why?

Riverine Habitats

Riverine Habitats

• River inhabitants (ribereños) actively manage these islands removing undesirable exotics, cultivating desireables (e.g. cacao, mango, rubber trees), and removing firewood

• They also are active agriculturalists planting many species of ag crop

Riverine Habitats

• Oxbows (resacas) provide another aquatic habitat (stagnation can occur)

Current Amazon

Riverine Habitats

Riverine Habitats

• Floating Meadows• There are giant floating masses of

grasses on large rivers• Largely ephemeral

Riverine Habitats

• Swamps (a woody vegetation that is innundated by standing water for a significant portion of the year)

• Most have limited sp richness..Why?

Riverine Habitats

Riverine Habitats

• There are several other bird species which have become ‘moriche specialists’

• M oriole, sulphury flycatcher, f-t palm swift, point-t palmcreeper

Riverine Habitats

• Floodplain Forests within the Amazon Basin cover 150,000km2 (e.g. FL)

• May border any type of river (which will influence the soil quality of forest)

• Fish are important fruit and seed consumers (and dispersers)

Riverine Habitats

• Many species are restricted to floodplain forests

Riverine Habitats

• Floodplain Forest is a relative term– Permanently water-logged swamp (oxbow)– Seasonally water-logged swamp (oxbow…)– Lower floodplain (low, but recognizable for)– Middle floodplain (tall for, occ flooded)– Upper floodplain (tall for, rarely flooded)– Old floodplain (within last 200 yrs)– Previous floodplain (ancient floodplain)

Riverine HabitatsNatural History

• Many wildlife species directly depend on riverine habitats

• It is estimated that 15% of nonaquatic Amazonian birds are directly dependent upon riverine habitats

Riverine HabitatsNatural History

• The fish diversity of the Amazon is tremendous

• Consider 2,400 sp (with 800 more likely there and not described)

• E.g. Tocantis (34 of 72 unnamed) • Almost 40% in two groups: characins

and catfish

Riverine HabitatsNatural History

• characins

Riverine HabitatsNatural History

• Catfish

Riverine HabitatsNatural History

• Other interesting fish

• Piranha can be somewhat controlled by the use of ‘timbo’, a local plant containing rotenone

Riverine HabitatsNatural History

• Other scary fish…

Riverine Habitats

• Interesting Fish• Pirarucu lungfish arawana

Riverine Habitats

• Around 200sp are fruit/seed eaters• Tambaqui (a characin) eat fruit (not

seeds…why?) exclusively for 5 mo

• Breed in black water, juveniles live in whitewater feeding on zooplankton

Riverine Habitats

• Aquatic Mammals

Riverine Habitats

Riverine Critters

• Giant Otter (1.5m)• Frequent oxbow lakes• Mean carnivores

Riverine Critters

• Capybaras (1.2m 55kg) are ecological equivalents to hippos

• Food source for caimen, jaguars, anacondas

Riverine Critters

• Anaconda (not a good pet)• Can reach 10m

Riverine Critters

• Crocodilians (9sp in Neotropics)

• There are caimans and alligators

• Many enemies as juveniles, only humans as adults

• Throughout the Amazon• Can impact food chain

Riverine Critters

• Turtles found in the Amazon belong to a family of side-necked turtles (Pelomedusidae)

Riverine Critters

• Giant Arran turtles can be found on river banks

• Considered end due to overhunting

Riverine Birds

• Going down (or up) the river, you could see 4 sp of vultures soaring, hawks, caracaras, and falcons perched in trees, flocks of parakeets, parrots and macaws flying overhead

Riverine Birds

• The hoatzin may be the most unique bird on the river

• Found in slow backwaters• Poor fliers• Usually in groups• Folivores • Claws and escape

Riverine Birds

• Sunbittern hunt small aquatic insects, vertebrates, and crustaceans

• Only sp in family

Riverine Birds

• Three sp of screamers are in slow waters

• Related to ducks• Excellent fliers

Riverine Birds

• Storks, herons and egrets

Riverine Birds

• Chestnut-bellied heron, elegant capped heron & tiger heron(s)

Riverine Birds

• Boat-billed Heron is an odd bird of the mangroves and riverbanks

• A noctural heron, bill may be sensitive

Riverine Birds

• Eight sp (2 Neotropical) of jacana (Charadriiformes) walk delicately on lily pads in marshlands and riversides

• Only males incubate eggs

Riverine Birds

• Kingfishers are one of the most visible birds on the rivers

• 5 sp in 5 sizes 38, 28, 23, 20, 14cm

• Their odd shape make them rather distinctive

Riverine Birds

• The 16 jacamars (Piciformes) are exclusively Neotropical (green or brown)

• While many nest in riverbanks, some nest in termite mounds

• Sally