La Plata River Dolphin

Pontoporia blainvillei

FIELD MARKS:

dolphinlike
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very small (~1.5m)
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cresent shaped blowhole
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long, distinct beak with many teeth
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small triangular dorsal fin
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Fresh and salt water habitats

Note

They are one of the smaller species of cetaceans.

Description

They range from 1.25 to 1.74m in length, with the females slightly larger than the males. They weigh anywhere from 20 to 61 kg at maturity. The cape color of these dolphins is grayish brown, but the side and belly surfaces are paler to almost white. The young are brownish in color, and have seven hairs on the upper rostrum that disappear with age. Their beak is extremely long and slender and is easily distinguishable from the bulging forehead. Their blowhole is uniquely transverse and in the shape of a crescent. The dorsal fin is triangular with a rounded tip, and ranges from 7.0 to 10.0cm in height. The neck is distinct and apparent, as in most river dolphins. There are 48-61 teeth in each side of the jaw, with the total ranging from 210-242. River dolphins are known to be mostly teeth!

Habitat

Most river dolphins live in rivers and/or coastal waters and estuaries, some venturing into freshwater lakes. Often living in muddy water, they have tiny eyes.

These are the only river dolphin (member of the superfamily Platanistoidea) that live in salt water. They are found in the estuary of the Rio de la Plata during most of the seasons, but during winter they migrate either out to sea or upwards along the coast of Brazil.

Range

Live only in South America.

Are found along the costal waters of South America from the Doce River in Brazil south to the Valdez Peninsula in Argentina. They are also common in the estuaries of the Rio de la Plata, hence the common name, La Plata dolphin.

Food

They inhabit waters that are sometimes murky from sediments. They locate bottom-dwelling species of fish by echolocation and by digging up the bottom with their long snout.

They are very picky eaters and in each area only a few species account for the majority of their food. In Uruguayan waters the most common fish is Cynoscion striatus. In Brazil, the most common are Paralonchurus brasiliensis, C. striatus, Macrodon ancylodon, and Micropongonias furnieri.

Females eat more squid than males. Juveniles eat more shrimp than adults.

Comments

Also known as the Franciscana.

Females breed once about every two years. Matings happen from December to February, births from September to December. Females lactate until the following August or September, and then rest for several months. The gestation period lasts from 9 to 10.5 months and lactation can take up to 9 months. The young are born about 0.75 - 0.80m in length and weigh about 7.3 - 8.5kg. Once the calf is born it takes up to 1-3 years to reach physical maturity and 2-3 years for sexual maturity.

They are not as playful as other dolphins and often shy away from boats.

The oldest female examined was 13 years old, and the female lifespan is thought to be about 15 years. This female did not show any eviedence of being senile. The oldest male was 16 years old, and the lifespan of males may be about 18-20 years.

Because of their pale colored bodies and their shy nature toward humans, these dolphins are known to local fishermen as "the white ghost".

Credits

Much of the information found here has been adapted from the following sources:

Brownell,Jr, Robert L. 1989. Handbook of Marine Mammals: Volume 4 River Dolphins and the Larger Toothed Whales. Academic Press, San Diego.

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