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Kingdom
Animalia
Phylum
Chordata
Subphylum
Vertebrata
Class
Mammalia
Order
Cetacea
Suborder
Odontoceti
Family
Phocoenidae
Species
Phocoenoides dalli
Phocoenoides dalli
Dall's porpoise
2010/02/07 04:27:09.523 US/Eastern
By Jeffrey Decker
Species:
Phocoenoides dalli
Geographic Range
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.
(
Genther, 2000
;
Klinowska, 1991
;
Reeves and Leatherwood, 1994
)
Habitat
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.
(
Klinowska, 1991
;
Reeves and Leatherwood, 1994
)
Physical Description
Mass
130 to 220 kg
(286 to 484 lbs)
Length
2.20 m (high); avg. 1.90 m
(7.22 ft; avg. 6.23 ft)
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
.
(
Genther, 2000
;
Klinowska, 1991
;
Reeves and Leatherwood, 1994
)
Reproduction
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.
Gestation period
11 months (average)
Time to weaning
24 months (average)
Age at sexual or reproductive maturity (female)
3 to 6 years
Age at sexual or reproductive maturity (male)
5 to 8 years
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.
(
Klinowska, 1991
;
Reeves and Leatherwood, 1994
)
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.
Lifespan/Longevity
Average lifespan (wild)
16.50 years
The average lifespan of a Dall's Porpoise is 16-17 years.
(
Klinowska, 1991
)
Behavior
Dall's porpoises usually occur in small groups of 10 to 20 individuals, although aggregations of at least 200 have been reported. They occur only rarely in groups of mixed species, although further north they are sometimes seen in the company of harbor porpoises, especially in the deep waters off Alaska and in Prince William Sound. They have also been spotted with gray whales. Migration north in summer and south in winter has been reported.
Dall's porpoises do not exhibit the typical shy and secretive behavior of most other porpoises. They are frequently seen charging boats and bow-riding. They are the fastest of the
phocoenids
and reach speeds of up to 35 mph. They frequently swim in a zig-zag pattern with fast, jerky, steep angled turns. Dall's porpoises may surface with a slow roll, a fast roll, or a rooster-tailing roll. The rooster-tailing roll is often used to identify the species in the wild. The spray resulting from this roll is a cone of water coming off the head of the porpoise which looks like a "rooster tail" due to the quick speed and steep angles at which the species surfaces.
(
Klinowska, 1991
)
Communication and Perception
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.
Food Habits
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.
(
Klinowska, 1991
;
Reeves and Leatherwood, 1994
)
Animal Foods:
fish; mollusks; aquatic crustaceans.
Predation
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
.
Ecosystem Roles
Dall's porpoises are important predators of fish and cephalopods in the ecosystems in which they live.
Economic Importance for Humans: Negative
Dall's porpoises have no negative effects on humans.
Economic Importance for Humans: Positive
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.
(
Reeves and Leatherwood, 1994
)
Conservation Status
IUCN Red List:
[link]
:
Lower Risk - Conservation Dependent.
US Federal List:
[link]
:
No special status.
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.
(
Klinowska, 1991
;
Reeves and Leatherwood, 1994
)
For More Information
Find
Phocoenoides dalli
information at
Contributors
Jeffrey Decker (author), University of Michigan.
Phil Myers (editor), Museum of Zoology, University of Michigan. Tanya Dewey (editor), Animal Diversity Web, University of Michigan Museum of Zoology.
References
Klinowska, M. 1991.
Dolphins, Porpoises and Whales of the World
. Gland, Switzerland: IUCN.
Reeves, R., S. Leatherwood. 1994.
Dolphins, Porpoises and Whales
. Gland, Switzerland: IUCN.
2010/02/07 04:27:10.872 US/Eastern
To cite this page:
Decker, J. 2002. "Phocoenoides dalli" (On-line), Animal Diversity Web. Accessed February 09, 2010 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Phocoenoides_dalli.html.
Disclaimer:
The Animal Diversity Web is an educational resource
written largely by and for college students
. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.
Other formats:
OWL
Sponsored in part by the Interagency Education Research Initiative,
the Homeland Foundation and the
University of Michigan
Museum of Zoology
.
This material is based upon work supported by the
National Science Foundation
under Grants DUE-0633095 and DRL-0628151.
The ADW Team gratefully acknowledges their support.
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