Franciscana Dolphin: Pontoporiidae

Franciscana dolphins usually swim alone or in small groups. Several dolphins may cooperate when feeding. They will swim The franciscana dolphin is called a river dolphin, but it spends its life in the ocean. (Illustration by Barbara Duperron. Reproduced by permission.) in a tight circle, surrounding the fish and pushing them together.

Franciscana dolphins are very quiet and shy at the surface. They rarely jump and often only raise their heads out of the water enough to breathe. They are preyed upon by sevengill sharks, hammerhead sharks, and possibly killer whales.

Female franciscana dolphins give birth to one calf after an eleven-month pregnancy. Most calves are born between October and January, spring in the Southern Hemisphere. Newborns are about 28 inches (71 centimeters) long and weigh 16 to 19 pounds (7 to 8.5 kilograms). They nurse, feed on their mother's milk, for about three months. After that, they continue to nurse, but also eat fish until they are completely weaned and not dependent on their mother's milk at about nine months. There is some disagreement about when these dolphins become sexually mature and able to reproduce. Estimates range from two to four-and-a-half years. Their average natural lifespan is about fifteen years.

Franciscana dolphins do not strictly migrate. However, it appears that in areas off the coast of Argentina where there is noticeable seasonal variation in water temperature, they may change their range. This movement does not seem to happen off the coast of Brazil, where water temperatures remain more constant throughout the year.