By Barbara Lundrigan and Liz Aubrey
Geographic Range
Found off the coast of Chile and as far South as the Tierra del Fuego. Found in areas of strong tidal flow above a steeply dropping continental shelf. Found in the coastal waters between Valpariaiso and Navarino Island (north of Cape Horn).
Biogeographic Regions:
pacific ocean 
(native ).
Habitat
They like shallow, muddy, and turbid waters. They are known to ascend rivers.
Aquatic Biomes:
coastal .
Physical Description
(57.2 to 162.8 lbs; avg. 110 lbs)
These dolphins have no beak. These dolphins have lots of teeth; 24 to 31 on each side of each jaw. The female is slightly larger than the male, so there is slight sexual dimorphism. They are called the black dolphin because the head, pectoral and dorsal fins, tail, and the posterior of back are all black. The belly, chin, sides, and anterior of the back are all white. The head and body length is 80-110 cm. The length of the pectoral fin is 15-30 cm. The width of the tail fluke is 30-40 cm.
Its rounded dorsal fin, 10-15 cm, distinguishes it from Burmeister's porpoise, which has a triangular dorsal fin with pointed tip and anterior knobs.
Some key physical features:
endothermic ; bilateral symmetry .
Reproduction
Females generally have one calf about every two years.
These dolphins mate in the early winter.
They mate as normal dolphins do in the early winter and they bear their young in the spring. Females generally have one calf about every two years. The lifespan of dolphins typically ranges from 25 to 65 years, it is not known whether these are typical.
Key reproductive features:
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous .
Behavior
This is a very shy species, found along coasts in groups of 8 to 14 individuals. There are some reports of aggregations of 20-50. They use echolocation. There are three sounds that they make: slow clicks, fast clicks, and cries.
Key behaviors:
natatorial ; motile ; social .
Food Habits
These dolphins feed on the sea bottom. They eat fish, squid, and crustaceans. They are able to eat solid food by six months of age.
Animal Foods:
fish; mollusks; aquatic crustaceans.
Economic Importance for Humans: Positive
This dolphin is moderately exploited for bait in the northern part of its range. In the western region of its range it may be exploited for crab bait. It may also be eaten by humans.
Conservation Status
IUCN Red List: [link]:
Data Deficient.
US Federal List: [link]:
No special status.
CITES: [link]:
Appendix II.
These dolphins are accidentally taken in gill nets.
Other Comments
Much is still to be learned about this species.
The name is taken from Greek, with "eu" meaning well or good, and "tropis" or "tropidos" meaning head or keel. This is probably because the skull has a strong keel in the back.
Contributors
Barbara Lundrigan (author), Michigan State University. Liz Aubrey (author), Michigan State University.
