Aquafacts / Pacific White Sided Dolphin

Pacific white-sided dolphins

Read some of the most frequently asked questions about Pacific white-sided dolphins, answered by our biologists.

Quick facts

2,000

A super pod of dolphins

46 years 

The oldest recorded age

15 kilograms

The average weight of a newborn

900,000

Number of Pacific white-sided dolphins in North Pacific

12 months 

Length of pregnancy

What does a Pacific white-sided dolphin look like?

Pacific white-sided dolphins are named because of the white colouration on their sides and underneath. They are dark grey on top and have a pale gray streak along each side that starts narrow above the eyes and then widens towards the tail. They have small dark beaks and dark rings around their eyes. Adult females can weigh 85-145 kg, and reach lengths of 1.7-2.4 m. Males can weigh up to 198 kg, and reach lengths of up to 2.5 m.

How many Pacific white-sided dolphins are there?

Pacific white-sided dolphins are the most abundant dolphin species in the North Pacific, estimated to be approximately 900,000 dolphins; however, very little is known about them in British Columbia (B.C.) waters and no accurate population estimate currently exists. Dolphins travel in groups throughout their lives. In B.C., Pacific white-sided dolphins are usually encountered in groups of 10 - 100 animals, although some groups have been seen with 2,000 or more individuals. The largest congregation of this species was reported offshore and was estimated to be close to 6000 individuals traveling together.

Where can you find Pacific white-sided dolphins?

Pacific white-sided dolphins are the most abundant dolphin species in the North Pacific, estimated to be approximately 900,000 dolphins; however, very little is known about them in British Columbia (B.C.) waters and no accurate population estimate currently exists. Dolphins travel in groups throughout their lives. In B.C., Pacific white-sided dolphins are usually encountered in groups of 10 - 100 animals, although some groups have been seen with 2,000 or more individuals. The largest congregation of this species was reported offshore and was estimated to be close to 6000 individuals traveling together.

Have there always been Pacific white-sided dolphins in British Columbia?

Pacific white-sided dolphins were first spotted by fisherman in 1956 north of Vancouver Island; however, sightings at the time were very rare in B.C.  In the mid-1980s researchers started to see a shift in the distribution of these dolphins – they were increasingly more common in coastal waters.  Were these dolphins exploring new habitats, or had they ever used these areas before?  The answer came in the mid-1980s from archeologist Donald Mitchell who was studying 2000 year-old First Nations middens in the Queen Charlotte Strait.  There he found the teeth of Pacific white-sided dolphins, showing that they had long been present on our coast.  Researchers aren’t sure why this species of dolphin was absent from our coast for several decades, but they suspect that changes in ocean temperature or fish populations may have encouraged their return.

What do Pacific white-sided dolphins eat?

Pacific white-sided dolphins are opportunistic predators feeding on over 60 species of fish and 20 species of cephalopods. In B.C. they feed on at least 13 different prey species, including salmon, herring, Pollock, shrimp, sablefish, smelt, and squid.  They forage cooperatively, though large groups may separate into smaller sub-groups for foraging purposes.  These feeding groups have been observed corralling and herding fish in a coordinated fashion.

Do Pacific white-sided dolphins use echolocation?

Whistle-like sounds help dolphins keep in contact and communicate with each other as they travel and feed. Dolphins use "echolocation" to find food or to scan their surroundings. They direct "clicks" into the water and the clicks rebound off solid objects (fish, logs, boats) and echo back to the dolphins. Dolphins listen for the strength of the rebounding clicks to identify what the object is and its distance from them. These clicks and whistles are created in the dolphin’s nasal passages just below their blowhole. The sounds are received by fat filled hollows in the lower jaw which then conducts the vibrations of the echo to the middle ear and brain for processing.

The ability of bottlenose dolphins to use echolocation was discovered in the 1950’s, and in the following decade scientists learned that most odontocetes (toothed whales, dolphins, and porpoises) have similar abilities. Since then, the echolocation capabilities of dolphins have been studied in considerable detail.  We now have a good sense of the types of objects that can be detected, and how echolocation detection abilities are reduced by background noise. However, despite this knowledge about what odontocetes are capable of doing with echolocation, surprisingly little is known when and why they do in fact use it.  Because dolphins are subject to eavesdropping by competitors, by fish, and even by potential predators when they echolocate, they may only use it when they really have to.  Learn more about an Ocean Wise study to better understand how dolphins use their echolocation to detect and capture prey and to avoid underwater hazards such as nets.

What predators do Pacific white-sided dolphins have?

Bigg’s (mammal-eating) killer whales (formerly called transients) and sharks are both known to prey on Pacific white-sided dolphins. When the dolphins first came back to B.C. coastal waters, it took the killer whales a couple of years to figure out how to catch the fast-moving dolphins. Some killer whale pods drove groups of dolphins into small bays and killed them en-masse but this behaviour is no longer as common, suggesting the dolphins have learned to avoid this trap.

Do Pacific white-sided dolphins interact with other marine species?

Pacific white-sided dolphins are often reported associating with other species.  One study in Monterey Bay, California reported half of all recorded sightings of Pacific white-sided dolphins were in association with another species.  In B.C.’s inshore waters they are seen with resident (fish-eating) killer whales, Steller sea lions, Dall’s porpoise, and humpback whales, among other species.  Offshore they are often reported with northern right whale dolphins, Risso’s dolphins, common dolphins, and short-finned pilot whales.

How long do Pacific white-sided dolphins live?

Pacific white-sided dolphins are believed to live about 40 years or more.

How do Pacific white-sided dolphins reproduce?

Pacific white-sided dolphins are mammals and give birth to live young. Females have their first calf when they are 7 to 9-years-old. Length of pregnancy (gestation period) is around 12 months. When the calves are first born they are approximately 1 m long and weigh roughly 15 kg. Females will nurse their calves for 8 to 10 months and give birth approximately every 4.5 to 5 years. In B.C. most newborn calves are sighted between June and August but researchers have yet to determine whether there is a defined calving season here.

Are Pacific white-sided dolphins endangered?

In Canada, Pacific white-sided dolphins are listed as “not at risk”, due to their large population numbers and wide distribution, but in many parts of their range across the North Pacific Ocean, these dolphins are taken both directly and indirectly in fisheries. During the 1980s, up to 90,000 Pacific white-sided dolphins were killed in the Japanese, Korean, and Taiwanese squid driftnet fisheries and the Taiwanese large-mesh driftnet fishery. Fortunately for the dolphins, these fisheries were discontinued following a 1992 United Nations resolution. In the late 1990s, there was a recorded decline in Pacific white-sided dolphins in the Broughton Archipelago, which correlated with the use of underwater acoustic deterrent devices by the salmon farming industries. These very loud sound sources were used to deter seals and sea lions from entering fish farms where they eat the farmed fish and cause significant damage to the farm infrastructure. Although acoustic deterrents have now been banned, ocean noise pollution is a problem that continues to threaten all cetaceans in B.C.

How can I help Pacific white-sided dolphins?

  • Participate in Citizen Science – Report your dolphin sightings using the WhaleReport app or visit www.wildwhales.org.  We’d love to hear about it!  Sightings give valuable information about species distribution patterns and helps in recovery and management planning.
  • Give them space – Make sure to always follow the Be Whale Wise Guidelines when watching dolphins, or visit Whale Trail BC locations and observe whales from land – a zero-impact alternative to whale watching.
  • Eat sustainable seafood – Know if your seafood is from a healthy, stable stock caught by environmentally friendly methods. Choose Ocean Wise Sustainable Seafood.
  • Dispose of waste responsibly – What goes down your drain eventually ends up in the ocean. Dispose of your hazardous waste at designated drop-off sites. Always reduce, reuse, and recycle.
  • Clean our shorelines – Garbage in the ocean poses a risk to all marine life, including Pacific white-sided dolphins and their prey. Help reduce marine debris by participating in the Great Canadian Shoreline Cleanup.

References

  1. American Cetacean Society. Pacific White-Sided Dolphin Fact Sheet
  2. Carwardine, Mark. 2000. Whales, Dolphins and Porpoises. New York: Dorling Kindersley Publishing.
  3. Ford, John K.B. 2014. Marine Mammals of British Columbia. Victoria: Royal British Columbia Museum.
  4. Heise, Kathy. 1997. “Life history and population parameters of Pacific white-sided dolphins (Lagenorhynchus obliquidens).” Report of the International Whaling Commission. 47: 817-825.
  5. Mason, Adrienne. 1999. Whales, Dolphins and Porpoises. Canmore, Alberta: Altitude Publishing.
  6. Morton, Alexandra. 2000. “Occurrence, photo-identification and prey of Pacific white-sided dolphins (Lagenorhynchus obliquidens) in the Broughton Archipelago,” Canada 1984-1998. Marine Mammal Science 16(1): 80-93.
  7. Wild Whales – BC Cetacean Sightings Network. Pacific White-Sided Dolphin

 

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