The northern right whale dolphin (Lissodelphis borealis) is a small, slender species of cetacean found in the cold and temperate waters of the North Pacific Ocean.

The northern right whale dolphin has a streamlined body with a sloping forehead, and a slimmer build than other delphinids.

[4][5] Its body is nearly all-black with a white ventral marking, extending forward as a narrow band from the caudal peduncle to the throat region, where the patch widens.

[6] In southern right whale dolphins (Lissodelphis peronii), the white patch extends higher on the posterior flanks and head.

Calves, which are born initially creamy-dark grey or brown, attain adult colouring by the age of one year.

Northern right whale dolphins have between 80 and 95 thin, sharp teeth, which are not externally visible, used for catching small fish and squid.

The mass of a mature testis was between 117.4 g to 1300 g. Gestation period was 12.1 to 12.3 months and calving seemed to peak during summer (July and August).

[10] Northern right whale dolphins are found in cold to temperate waters, 8 to 24 °C (46 to 75 °F), of the North Pacific Ocean.

However, L. borealis has been reported as far south as 29° N, off Baja California (Mexico), during times of anomalously cold water temperatures.

Based on the analysis of complete cytochrome b sequences, LeDuc et al. (1999)[17] suggested placing the northern right whale dolphins (together with Lagenorhynchus spp.

[18] Genetically, no statistically significant differences have been found between northern right whale dolphins from the US coast and other regions within the North Pacific.

Their abundances and distributions along the US coast do not only vary seasonally but also interanually, making the identification of population trends difficult.

[7][22] It is thought that in contrast to coastal areas, the offshore habitat of the northern right whale dolphin is generally less susceptible to human pollution.

[23] Natural predators of Lissodelphis borealis are unknown, but may include the killer whale (Orcinus orca) and large sharks.

[25] Furthermore, these YouTube videos show the surface behaviour[26] of a superpod of northern right whale dolphins and the typical sounds that they produce.