As in most phocoenids, Dall's porpoises use a form of echolocation to navigate, capture prey, and perhaps to communicate with conspecifics. They also use a variety of audible clicks and whistles. They may also use touch for social communication.
Communication Channels: tactile ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Dall's porpoises are not directly exploited in the eastern Pacific, but serious conservation problems are centered in the western Pacific where, during the 1980's, Dall's porpoises were intensely hunted. Estimates suggested 40,367 Dall's porpoises were killed in 1989 from the Japanese hand-harpoon fishery alone. In recent years these numbers have declined because of the Japanese government's effort to regulate the hand-harpooning of these animals. In 1992 11,403 were killed. This species is often killed accidentally in the Japanese seas and off of North America by drift nets set for salmon. It has been estimated that up to 20,000 porpoises are entangled and drowned in these nets off of Japan and up to about 4,100 off of North America annually. Due to international negotiations between Japan and the United States, along with new fishing gear and techniques, the incidental take has been reduced drastically. However, the conservation of Dall's porpoises remains a major issue.
US Federal List: no special status
CITES: appendix ii
IUCN Red List of Threatened Species: least concern
Dall's porpoises have no negative effects on humans.
The only direct commercial harvest of Dall's porpoises is a traditional coastal harpoon fishery in Japan which accounts for annual harvests of about 6,000 animals to compensate for the shortage of whale meat. Dall's porpoises contribute to marine ecotourism through their gregariousness and their aquatic antics.
Positive Impacts: food ; ecotourism
Dall's porpoises are important predators of fish and cephalopods in the ecosystems in which they live.
Dall's porpoises apparently feed at night and depend to some degree on the deep scattering layer, that is the fauna which travels upwards each night from the deeper parts of the ocean's water column. Food species as determined from stomach contents include squid and other cephalopods, lanternfish, Pacific hake, jack mackerel, herring, sardines, and crustaceans. Dall's porpoises are thought to be capable of deep diving because mesopelagic, bathypelagic, and deep-water benthic species are represented in the diet.
Animal Foods: fish; mollusks; aquatic crustaceans
Primary Diet: carnivore (Piscivore , Molluscivore )
Dall's porpoises, Phocoenoides dalli, are cool water porpoises inhabiting the North Pacific Ocean and adjacent seas. The central Bering Sea marks the northern boundary of their range and, although they prefer colder water, Dall's porpoises are found in the warmer waters of Baja California on the east to southern Japan on the west. They are frequently observed in these lower latitudes during the winter months. There are potentially two subspecies of Dall's porpoises, although they may simply be color morphs, P. dalli dalli and P. dalli truei. Phocoenoides dalli truei is abundant only off the Pacific coast of northern Japan.
Biogeographic Regions: pacific ocean (Native )
Generally the colder waters of the North Pacific are home to Dall's porpoises. They are observed inshore and offshore. They are a deep water species, so when they approach the coast they usually follow canyons or deep channels. They are also commonly observed in sounds and inland passages where these meet the open sea.
Habitat Regions: temperate ; polar ; saltwater or marine
Aquatic Biomes: pelagic ; coastal
The average lifespan of a Dall's Porpoise is 16-17 years.
Average lifespan
Status: wild: 16-17 years.
Average lifespan
Status: wild: 22.0 years.
Average lifespan
Status: wild: 17.0 years.
Dall's porpoises are the largest of the phocoenids. They typically reach a length of 1.8 to 2.0 meters, rarely more than 2.2 meters. At birth, the length is between 0.85 and 1.0 meters. Weight in adults varies from 130 to 220 kilograms. The body is stocky and more powerful than other members of Phocoenidae. The head is small and lacks a beak although there is a sloping forehead. The flippers are small, pointed, and located near the head. The dorsal fin is triangular in shape with a hooked tip.
There are three color patterns observed in the Dall's porpoises. The first is a uniform black or white throughout the entire body. The second pattern consists of intermixed stripes of black and white running along the length of the body. Finally, there is the most common color pattern observed, that of P. dalli dalli. This is defined as having a dorsal area uniformly black with a white ventral side. The white ventral patch begins far behind the flippers. The dorsal fin, flippers, and fluke are black with some white at the tips. The color pattern of P. dalli truei is different only in the distribution of the white ventral patch. The white patch begins ahead of the flippers rather than far behind them, and P. dalli truei is often longer and slimmer than P. dalli dalli.
Range mass: 130 to 220 kg.
Range length: 2.2 (high) m.
Average length: 1.8-2.0 m.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry ; polymorphic
Sexual Dimorphism: sexes alike
Killer whales and sharks are believed to be the primary natural predators of Dall's porpoises. They largely escape predation through their large body size, agility in the water, and their habit of traveling in groups. Their coloration may make them difficult to see in the water as well.
Anti-predator Adaptations: cryptic
Little is known about mating in cetaceans, especially in species which occur primarily offshore. Mating systems in Dall's porpoises are unknown.
Little is known about the reproductive biology of Dall's porpoises. Two calving periods have been reported for portions of the eastern North Pacific, one in winter, from February through March, and the other in summer, from July through August. Some segregation of animals seems to occur with juveniles found closer to shore and larger adults well offshore. In offshore areas, females in late pregnancy or lactation seem to be distributed in northern areas, and southern areas are mainly occupied by males and females not accompanied with calves. This seems to indicate that not all females become pregnant every year. Females usually reach sexual maturity between the age of 3 to 6 years, whereas males reach sexual maturity between the ages of 5 to 8 years. Gestation is believed to last about 11 months, and lactation periods are usually about 2 years.
Phocoenoides dalli dalli appear to have three major breeding grounds. Two occur in the North Pacific north of 45 degree latitude, and another breeding site occurs in the central Bering Sea. Phocoenoides dalli truei may breed off the northern coast of Japan.
Breeding interval: Individual females probably do not breed every year. Breeding intervals may be as long as 3 to 4 years because of the length of dependence of calves.
Breeding season: Mating is likely to occur after the calving seasons each year which occur in winter, from February to March, and in summer, from July to August.
Average gestation period: 11 months.
Average weaning age: 24 months.
Range age at sexual or reproductive maturity (female): 3 to 6 years.
Range age at sexual or reproductive maturity (male): 5 to 8 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
Average gestation period: 347 days.
Average number of offspring: 1.
Females feed and care for their offspring for extended periods of time. It is likely that some form of extended learning occurs during this period as well. Male parents do not contribute parental care.
Parental Investment: no parental involvement; precocial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); extended period of juvenile learning
