(Pontoporia blainvillei)

INFORMATION AND CHARACTERISTICS.

It is one of the smallest dolphins in the world and curiously, although it is a member of the group of river dolphins, it does not live exclusively in freshwater. This dolphin was described initially in 1844. Also known with the name of Franciscana dolphin, it is the only member of its family.

Order: Cetacea
Superfamily: Inioidea
Family: Pontoporiidae
Genus: Pontoporia

HOW DO THEY LOOK? PHYSICAL CHARACTERISTICS.

This dolphin rivals Hector’s dolphin (Cephalorhynchus hectori) for the title of the “smallest dolphin in the world, ” but the individuals of this species have slightly larger dimensions.

Weight and size.
La Plata dolphin females grow faster than males, and the former are also larger than the latter when adults. A female length is around 1.8 meters; The male is only 1.6 meters. Other estimates indicate that females and males can be as small as 80 and 76 centimeters, respectively. The weight is around 50 kilograms.

Morphology.
From their small body stands a large beak and a big head with symmetric facial skull and a rounded forehead. Their fused vertebrae provide a very flexible neck. Just above the fold of the neck is the blowhole which has a semilunar shape and several centimeters further back appears a medium-sized dorsal fin, with a triangular shape and a rounded tip. They have flattened pectoral flippers, where small ridges protrude in males when they reach adulthood.

Skin Coloration.
The color of the dorsal area (top) is usually gray or brownish. The belly is white. Young specimens tend to be browner than adults, and they have seven hairs on the upper jaw.

Distinctive characteristics.
Its narrow beak is the most outstanding feature as it has the largest ratio of all cetaceans when comparing its body size against its beak.

WHERE DO THEY LIVE? DISTRIBUTION AND HABITAT.

It is distributed only along the eastern South American coasts of the Atlantic Ocean from Brazil to Argentina, passing through Uruguay in tropical and temperate waters. It inhabits from the north of the San Matías Gulf in Argentina to the state of Espírito Santo in southeast Brazil. This range is misleading because the species is not evenly distributed in it but is absent in some areas.

It lives about 55 kilometers from the coasts in murky and shallow ocean waters with depths ranging from 6 to 35 meters, but they venture into brackish estuaries. Tides have a significant influence on their habitats.

WHAT DO THEY EAT? DIET AND EATING HABITS.

It consumes a wide variety of pelagic and demersal fish, as well as cephalopods and crustaceans. It is, therefore, a carnivorous animal whose teeth serve to hold the prey, including shrimp and squid.

Most of their prey have lengths around 10 centimeters, but they can consume everything that fits into their mouth. Their favorite prey is:

– Longfinger anchovy (Anchoa filifera).
– American Coastal Pellona (Pellona harroweri).
– Corvina (Isopisthus parvipinnis).
– Squid (Loligo sanpaulensis).
– Cynoscion striatus.
– Blonde Corvina (Micropogonias jurnieri).
– Banded Croaker (Paralonchurus brasiliensis).

This dolphin spends a lot of time looking for food during the high tide and displays cooperative hunting techniques in which all members of a group help to catch food.

HOW DO THEY BEHAVE? BEHAVIOR

The La Plata dolphin is a diurnal cetacean which performs its principal activities during the day. Although it is sociable as many other dolphins, their pods are composed of 2-15 individuals but can be as many as 20 or 40. The social structure is possibly matriarchal, that is when an adult female lead the pod and the groups are made up of individuals related to each other.

It is not common to spot this dolphin, and its movements are regularly slow: its speed when swimming is 0.09-1.8 meters per second. If the tide is low, it travels with the members of its pod.

HOW DO THEY REPRODUCE? MATING AND REPRODUCTION.

Unusual in the world of dolphins, this species is believed to be monogamous and reach sexual maturity early in life. Females reach sexual maturity at around three years and males at two, but this varies among populations of the north and the south of its range of distribution.

Females have one offspring each year between October and January after a mating usually between January and February. These times indicate that the gestation period lasts 10.5-11.2 months.

The calf spends a lot of time with its mother and for a time is fed only with breast milk. At 8-9 months of age is weaned, when it measures about 105 centimeters in length.

WHAT IS THEIR CONSERVATION STATUS? THREATS AND CONSERVATION.

Conservation Status: Vulnerable.

The La Plata dolphin has a conservation status of “Vulnerable” according to the classification of the Red List of the International Union for the Conservation of Nature (IUCN). This situation is the result of bycatch in gillnets, the contamination of their habitat and the noise pollution. Its high mortality is, therefore, a consequence of human activities, and 500-800 individuals of this species die every year.

La Plata dolphin is in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which lists species whose trade requires strict regulation.

References

http://www.cms.int/reports/small_cetaceans/data/P_blainvillei/p_blainvillei.htm

Jefferson, Webber, Pitman. Marine Mammals of the World: A Comprehensive Guide to Their Identification. Academic Press, 2015. Page 355.

http://www.iucnredlist.org/details/17978/0

http://ar.whales.org/guia-de-especies/franciscana

Introduction

There are only five species of dolphins that are able to thrive in freshwater and the Amazon River Dolphin is one of them. Many people assume that all dolphins live in saltwater so this is interesting to learn if you weren’t aware of it. There are several subspecies of River Dolphins to learn about.

Description

Depending on the location where they reside, River Dolphins will vary in size. Some of them can be up to 8 feet long but most of them are much smaller than that. They can also be found in a variety of colors. Some that you are known to exist include gray, black, brown, pink, yellow, and white. Due to the many different colors, they are often mistaken for other forms of aquatic life.

Distribution

The River Dolphin, as the name implies, lives in Rivers and that means they are able to survive in freshwater. They tend to stick to the brackish and coastal regions. They are found in the

Amazon, Ganges, Yangtze, Mekong, and Indus Rivers. Many of these rivers are home to very poor villagers and the locations can be very dense.

Plenty of these rivers are filled with dark, murky water and plenty of pollution. What is very interesting is that they can live in conditions that other species of dolphins would not be able to. It isn’t understood why this is possible, and more research has to be done. With so few species being able to live in freshwater, there are some theories but no definite answers at this time.

Behavior

River Dolphins are very social, and like others, they form pods. There can be just a few of them or more than 100 in a pod. They do form very strong bonds and they are quite protective of each other. The young tend to be secured in the middle of the pod in order to keep them safe. The females have also been noted to care for the young of each other in a cooperative effort.

These dolphins are believed to be very social and to have a complex hierarchy that can be hard to fully understand. They tend to have some pods that have primarily females or males in them. This could be part of their social organization.

Feeding

Fish are the main components of the diet for the River Dolphin, and they can eat large amounts of them daily. They use a variety of differenttechniques to get the schools of fish with ease. Usually, these efforts involve teamwork and collaboration that is very in sync and interesting to observe. For larger pods, they often break up into smaller groups for feeding purposes to be carried out.

Reproduction

The time of year for mating can vary based on the location of the River Dolphin. The females usually are ready to mate around 8 years of age and for the males it is about 10 years old. The males may heavily compete with each other for mating. The young will be born from 10 to 12 months later, tail first.

The pod is very protective and they will help the mother during the birthing process. They will protect the young calf and help it to the surface for air. They will also help keep predators away. The young will grow rapidly due to the fat content found in the milk that the mother produces. They will drink the milk for 1 ½ to 2 years, but they will also start to consume fish when they are about 6 months old.

Conservation Status and Threats

The River Dolphin is considered to be in a range from vulnerable to critically endangered. It is hard to get a good idea of the number of them due to the different species and their habitat. There are plenty of issues for the River Dolphin to worry about in their natural habitat. They may be caught up in fishing nets or collide with boats. Heavily pollution has played a vital role in the reduction of numbers of them in many locations.

Some of the conservation efforts involve fishing with better equipment and tools. However, since the rivers where plenty of the dolphins live are around very poor cultures that can be tough to improve. Overfishing is also a concern as the villagers heavily depend on the food for survival. Yet that can leave a lack of food for the dolphins to survive. Pollution problems are also higher in areas where they don’t have proper water and sewer systems in place.

One of the River Dolphins called the Baiji, has declared functionally extinct in December of 2006. The last time one of them was seen in the wild was in 2004. While there were some reports in 2007 of sightings of one in the Yangtze River, it couldn’t be confirmed.