The North Pacific right whale is one of the giant whales and its head takes up about one third of its body length, and seems almost disproportionately large. Its seven neck vertebrae fuse into a single mass, and it has hardened layers of skin on its head, lips and chin, usually covered in whale lice and called callosities. Its body is broad and robust, and it has large, wide pectoral flippers. The upper jaw is the shape of an arch, from which hang its large, slender baleen plates. Its color is usually black; often it has a mottled appearance or white ventral patches.
This whale occurs throughout the North Pacific Ocean, from Russia and Japan in the west to North America's west coast and Alaska in the east. The population of the western North Pacific spends summer in the Okhotsk Sea and is occasionally sighted off Japan's east coast. The Northeast Pacific subpopulation summers in the southeastern Bering Sea and Gulf of Alaska. North Pacific right whale mainly inhabit coastal or shelf waters, however, movement over deep waters has been observed.
North Pacific whales can generally be found traveling on their own or in pods of just 2-3 whales. Larger groups may travel together during the mating season. It is thought that right whales remain in the same region for days or sometimes weeks. North Pacific right whales migrate from summer to winter grounds. They are generally regarded as non-aggressive, and what can be described as tender, towards others of their species, including competing males, potential mates, and young. Although slow, they are surprisingly acrobatic, and are known for breaching, as well as slapping their flippers against the water's surface when they roll over. They are curious, playful animals, and often bump and poke objects they come across in the water. They sometimes raise their tail flukes above the water as sails, a form of play.
These whales are polyandrous, with females likely to mate with many males, while males do not aggressively compete for females. Mating behavior in right whales includes tail and fin slapping at the surface, breaching and "headstanding". Breeding generally occurs in winter, and, after a gestation period of 12-13 months, females give birth to a single calf. Mothers protect, nurse, and care for their offspring, putting significant amounts of energy into each one. A calf remains close to its mother and suckles for about a year. The female typically uses the third year to replenish her energy stores before mating again, so there are intervals between of three to five years. These whales are sexually maturity from about 8 – 11 years old, at which time they may bear their own offspring.
It is not possible to assess every threat to this species, due to their scattered distribution and rare occurrence, but they could include entanglement in fishing equipment and collisions with passing ships. Environmental changes and pollution may also be threats.
According to the IUCN Red List, the total number of the North Pacific right whale is around 500 individuals, including approximately 400 whales in the Okhotsk Sea and around 100 whales for the rest of the North Pacific. Overall, these whales are classified as Endangered (EN) and are currently on the list of threatened species.