Rough-toothed Dolphin - Steno bredanensis

Rough-toothed Dolphin
Steno bredanensis

Other Names: Slopehead

Habitat: Offshore

Status: Unknown

Population: Unknown

Threats: Hunting/whaling and entanglement in fishing nets

Group Size: 10-20, occasionally in groups of several hundred

Fin Position: Center

Newborns: c.39 in (1 m), Unknown weight

Adults: 7-8 ½ ft (2.1-2.6 m), 220-230 lb. (100-150 kg)

Diet: Fish and squid or octopus

Teeth: 32-52 on top row, 38-56 on bottom row

Description

Dorsal fin:

- pointed tip
- trailing edge always concave
- wide base
- leading edge usually at 45° angle to body
- fin may be highly falcate in shape

Flukes:

- slightly pointed tips
- distinct notch in middle
- concave trailing edges
- broad flukes

Flippers:

- large, pointed flippers

Other characteristics:

- long, narrow beak
- conical head
- smoothly sloping forehead without crease between beak and forehead
- dark gray or bluish gray cape may have purplish hue
- body robust in front of dorsal fin
- body slimmer behind dorsal fin
- dark gray or bluish gray tail stock
- some animals may be highly scarred
- keels below and above tail stock
- pinkish or yellowish white blotches and spots, especially on lower half of body (variable)
- sides paler than upper side and may have purplish hue
- dark patch around large eyes
- white or purplish white "lips" and throat (variable)

Behavior

- difficult to observe as may stay submerged for as long as 15 minutes
- rarely does more than a half-hearted breach
- fast swimmer, sometimes porpoising with low, arc-shaped leaps
- may swim rapidly just under the surface, with dorsal fin and small part of back clearly visible
- sometimes bow-rides, especially in front of fast-moving vessels, though not as readily as many other tropical dolphins
- may associated with Bottlenose Dolphins and pilot whales and, less frequently, with spinner dolphins and spotted dolphins; sometimes associates with shoals of Yellowfin Tuna
- may be seen logging

Distribution

- deep tropical, subtropical, and warm temperate waters around the world
- distribution poorly known
- appears to be widespread in warm waters around the world, normally where sea surface temperature is above 77° F (25° C), and seems to avoid cold surface waters and cold currents
- does not appear to be particularly numerous anywhere, although researchers have worked mostly in the eastern tropical Pacific and may simply have missed areas of high abundance elsewhere
- there have been many more sighting in recent years, especially around Hawaii; and a number of recent sightings off the coast of Brazil suggest a more southerly distribution in the Atlantic
- appears to be a permanent population in the Mediterranean
- most often found in deep water far offshore, usually beyond the continental shelf

e-mail questions, comments, and/or suggestions to
wcrc@sci.tamucc.edu

Internet Coordinator: Candice Orca Mottet

e-mail questions, comments, and/or suggestions to wcrc@sci.tamucc.edu

e-mail questions, comments, and/or suggestions to
wcrc@sci.tamucc.edu