Franciscana, Toninha, Cachimbo, La Plata dolphin
The La Plata dolphin, franciscana or toninha (Pontoporia blainvillei ) is a species of dolphin found in coastal Atlantic waters of southeastern South America. It is a member of the river dolphin group and the only one that lives in the ocean and saltwater estuaries, rather than inhabiting exclusively freshwater systems. Commercialized areas that create agricultural runoffs and industrialized zones can affect the health of the La Plata dolphin, especially in regards to their contributions of waste and pollution, which can lead to habitat degradation and poisoned food among other concerns.
The La Plata dolphin is a member of the river dolphin group and the only one that lives in the ocean and saltwater estuaries, rather than inhabiting exclusively freshwater systems. The body of this dolphin is a greyish brown colour, with a lighter underside. The flippers are also very large in comparison with body size and are very broad, but narrow on joining the body, so are almost triangular in shape. The crescent-shaped blowhole lies just in front of a crease in the neck, giving the impression that dolphin forever has its head cricked upwards. The La Plata dolphin also has the longest beak (as a proportion of body size) of any cetacean.
La Plata dolphins are found in the Atlantic waters of southeastern South America, including the Río de la Plata estuary. Their distribution ranges from the Tropic of Capricorn near Ubatuba, Brazil, south to Península Valdés, Argentina. La Plata dolphins inhabit shallow coastal waters but also clear waters and saltwater estuaries. They usually occur in depths ranging from 8 to 35 meters and rarely venture further away from the shore.
La Plata dolphins are diurnal very inconspicuous animals. They move very smoothly and slowly and can be difficult to spot unless estuary conditions are very calm. When swimming, river dolphins rely on their tail fins to propel themselves through the water. Flipper movement is continuous and they swim by moving their tail fins and lower bodies up and down, propelling themselves through vertical movement, while their flippers are mainly used for steering. La Plata dolphins usually swim alone or in small groups but may gather in pods as large as 15 individuals. They are generally quiet in nature but may communicate with each other through high-pitched clicks and whistles.
La Plata dolphins are carnivores (piscivores). They are bottom feeders and eat at least 24 different species of fish. They will also take octopus, squid, and shrimp.
La Plata dolphins are believed to be serially monogamous and may remain with one partner during a breeding season or a portion of that season. Calves are usually born around September to February (during the austral spring and summer), following a 10-11 month gestation period. The young are 70 to 75 cm when born and are weaned at a year old. Reproductive maturity is reached between 2 to 3 years for both sexes, however, some populations start to breed when they are 5 years old.
La Plata dolphins are threatened by habitat destruction and water pollution. Commercialized areas often have agricultural runoff or industrial zones that are harmful to the species' health. Waste and pollution from these areas lead to habitat degradation and toxic chemicals in fish that dolphins feed on. La Plata dolphins also face threats from fishing nets and other types of fishing gear that they get caught in while searching for prey.
The IUCN Red List and other sources don’t provide the number of the La Plata dolphin total population size. According to MarineBio Conservation Society, there are about 40,000 individuals of this species occur off the coasts of Brazil and Uruguay. Currently, the La Plata dolphin is classified as Vulnerable (VU) on the IUCN Red List and its numbers today are decreasing.
