Each of these characters is found also in at least one species of some other odontocete family, but the combination is found only in the Phocoenidae. They normally are slow swimmers and almost never accompany vessels. Phocoenoides usually inhabits oceanic waters, though it also enters fjords and straits with deep, clear water. It is among the swiftest of cetaceans and habitually races ahead of vessels. It feeds on deep-dwelling squid and fish.
Porpoises usually travel in small groups.
Females have a gestation period of about 11 months and give birth during the warm months. The Johns Hopkins University Press. All rights reserved. This document may be used, with this notice included, for noncommercial purposes within a purchasing institution . No copies of this work may be distributed electronically outside of the subscribed institution, in whole or in part, without written permission from the JHU Press .