The teeth of the female are slightly smaller than those of the male. B. bairdii are a blueish grey color, often with a brown tinge. Their undersides are usually lighter with three patches of white on the throat, between the flippers, and near the navel and anus. These spots range in size from barely visible to an almost continuous stripe across the belly. Two grooves run along the underside of the jaw in a wishbone shape.
Females tend to be lighter in color than males, who often have tooth scars on their beaks.
These whales are deep divers and feed most often on squid, particularly Gonatus fabricii . They also eat octopus, lobster, crab, rockfish, and herring. Reproduction Most B. bairdii reach sexual maturity when they are about 9.4 meters long for males and 10 meters long for females. They mate in mid-summer in warm waters near Japan and California. The gestation period is thought to be approximately ten months, though pregnancies of up to 17 months have been reported.