Northern Rightwhale Dolphin - Lissodelphis borealis

Northern Rightwhale Dolphin
Lissodelphis borealis

Other Names: Pacific Rightwhale Porpoise

Habitat: Offshore and occasionally inshore

Status: Common

Population: Unknown

Threats: Entanglement in fishing nets and hunting/whaling

Group Size: 5-200, up to 3,000 have been observed together

Fin Position: No fin

Newborns: c.32-39 in (80 cm-1 m), Unknown weight

Adults: 6 ˝-9 ž ft (2-3 m), c.130-220 lbs. (60-100 kg)

Diet: Squid or octopus and fish

Teeth: 74-98 teeth on both top and bottom rows

Description

Flukes:

- undersides predominately white
- concave trailing edges
- distinct notch in middle
- pointed tips
- narrow flukes

Flippers:

- pointed tips
- small, slender flippers

Head:

- narrow head
- white area behind tip of lower jaw
- short, slender beak
- lower jaw extends beyond tip of upper jaw
- beak clearly demarcated from forehead by groove
- gently sloping forehead

Other characteristics:

- no dorsal fin
- black upper side and sides sometimes have a brownish sheen
- long, slender body
- extremely narrow tail stock
- band of white in naval area broader in males than females
- sharp dividing line between black and white
- white chest patch with connecting line to flukes

Behavior

- when traveling fast and leaping, overall impression is of a bouncing motion; each leap can be up to 23 ft (7 m) long
- easily startled
- when fleeing, group typically gathers in tight formation, with many animals leaping simultaneously, and often working the sea into a froth
- it may also swim slowly, causing little disturbance of the water and exposing little of itself at the surface
- breaching, belly-flopping, side-slapping, and lobtailing fairly common
- may bow-ride, but usually avoids boats
- body leaves water in low-angle leaps when porpoising out of the water

Distribution

- cool, deep temperate waters of the northern North Pacific
- widely distributed
- occurs in the western North Pacific from Kamchatka, Russia, to Japan, and in the eastern North Pacific from British Columbia, Canada, to northern Baja California, Mexico
- may also occur in the northern Sea of Japan
- sometimes ventures farther south when surface temperatures unseasonably low
- seems to be an area of very low density immediately south of the Aleutian Islands, Alaska, perhaps separating the eastern and western populations
- mainly found in deep waters over the continental shelf and beyond
- may sometimes go inshore, where there are deep canyons
- in some areas, may migrate southward and inshore for winter and northward and offshore in summer

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