Franciscana Dolphin: Pontoporiidae

Franciscana dolphins are also called La Plata dolphins, because the first described specimen, or animal, came from the mouth of La Plata River, Uruguay, in 1884. These dolphins are considered river dolphins, even though they live in the ocean near the shoreline. Originally scientists thought that the franciscana dolphin moved from fresh water to salt water during its lifetime, but now they know that it spends its entire life in the ocean. In the past, franciscana dolphins have been classified in several different dolphin families, but they are currently classified in a family of their own.

The franciscana dolphin is one of the smallest members of the cetacean order. They measure between 4.4 and 5.7 feet (1.3 and 1.7 meters) and weigh between 75 and 115 pounds (34 and 53 kilograms). Females are larger than males. Franciscana dolphins are gray-brown on their back and lighter underneath. Young franciscana dolphins are darker than older animals. Very old animals can appear almost white.

The most notable feature of the franciscana dolphin is its long, slender beak, or snout. They have the longest beak of any dolphin. Their beak may be 15 percent of their body length. Franciscana dolphins have triangular dorsal, or back, fins with rounded tips. Their flippers are broad and short. This dolphin has between 208 and 242 teeth small teeth. The blowhole, or nostril, is a crescent-shaped slit. Unlike the Ganges and Indus river dolphins, franciscana dolphins have good eyesight.

Even though franciscana dolphins can see well, they use echolocation (eck-oh-loh-KAY-shun) to find food and navigate through their environment. The forehead of a dolphin is a lump of fatty tissue called the melon. Echolocation is a sensory system in which dolphins make sounds that seem to be focused through the melon and then sent out into the environment. When the sounds bounce back, the echo is passed through special tissue in the lower jaw to the inner ear. From the time it takes to collect the echoes, their strength, and their direction, dolphins construct a "sound picture" of their environment. This system is extremely sensitive and allows the animal to locate very small objects. Scientists disagree about just how the dolphins actually make the sounds.