Overall, they tend to be dwarfed by other cetaceans. Calves and their mothers live separate from main porpoise herds for a time. These commonly seen fun-loving playful porpoises can only be found in the North Pacific Ocean where they prefer cooler water temperatures between 36 and 60 degrees (2C-15C). Dall. The Dall's porpoise is easily identified by it's very unique black and white markings and is named for the naturalist who first discovered them, W.H. Almost all species have female-biased sexual dimorphism, with the females being larger than the males, although those physical differences are generally small; one exception is Dall's porpoise. Odontocetes possess teeth with cementum cells overlying dentine cells. Dall's porpoise calves are born in mid-summer after a 12 month gestation period. They are about 3 feet (0.9 meters) long. Dall's porpoise has an extremely robust and muscular body, especially through the mid-section, and the male is considerably thicker than the female.