(Gervais and d'Orbigny, 1844) - Franciscana
Distinctive Characteristics
Although not a true freshwater dolphin, this primarily marine species is nonetheless related to them. The beak is extremely long and narrow, and the forehead is steep and rounded. The dorsal fin is low to moderately tall and triangular, with a rounded tip. The flippers are broad and spatulate, with an undulating trailing edge. In many subadults, there are visible ridges along the surface, corresponding to the flipper bones. In calves, the beak is much shorter and stouter than it is older animals.
Franciscana are countershaded brownish to dark grey above, and lighter brown (or even yellowish) to grey below and on the lower flanks. A faint dorsal cape is present.
The long beak is lined with 50 to 62 fine pointed teeth per row, more than in nearly any other species of cetacean.
Recent morphological studies have documented the existence of 2 forms of franciscana, a smaller northern and a larger southern one.
Can be confused with
Young franciscana may be confused with marine dolphins of the genus Sotalia, but can be identified by their very long beaks and more rounded dorsal fins.
Size
Males reach 1.63 m, and females 1.77 m in length. Maximum recorded weight is about 34 kg. At birth, franciscana average about 75 cm.
Geographical Distribution
Franciscana are found only along the east coast of South America, from central Argentina to central Brazil. They are primarily coastal, but may be found in some estuaries, and sporadically enter the la Plata River.
Biology and Behaviour
There is very little known about the franciscana's natural history. They are found in small groups of up to 5 individuals. In general, they appear to avoid vessels.
Peak calving for this species is in November and December.
Franciscana feed mostly near the bottom on several species of fish, cephalopods, and crustaceans.
Exploitation
Although there are no estimates of abundance, the franciscana is not thought to be in serious danger of extinction. Because they do not live in rivers, these animals are not as burdened with some the threats facing other members of the family. However, incidental catches, mostly of juveniles, in gillnets for sharks and other species of fish are a serious problem. Some commerce in parts from accidentally caught dolphins has been documented. Other environmental problems include pollution of habitat, the effects of vessel traffic, and environmental contaminants.
IUCN Status
Insufficiently known.