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Table of Contents
The Pacific White-sided Dolphin (Lagenorhynchus obliquidens), also known as the hookfin porpoise, is a highly active dolphin that mixes with other cetacean species in the calm waters of the North Pacific Ocean.
See the fact file below for more information on the Pacific White-sided Dolphin, or you can download our 28-page Pacific White-sided Dolphin worksheet pack to utilize within the classroom or home environment.
Key Facts & Information
- Pacific white-sided dolphins are known as the hookfin porpoise because of their large recurved and bi-colored dorsal fin. In comparison to their overall body size, they have a robust body, a short rostrum (snout), and a large dorsal fin.
- They have three distinct colors, white, gray, and black. The chin, throat, and belly are creamy white, while the beak, flippers, back, and dorsal fin are dark gray. The large flippers of these dolphins are slightly rounded at the tips. On the sides, there are light gray patches.
- Grey “suspender stripes” start above the eye to below the dorsal fin and widen into bands on the sides of the tailstock.
- A dark-gray ring surrounds the eyes, while the area at the tip of the snout, or “lips,” is black.
- The weight of an average adult Pacific white-sided dolphin is between 300 and 400 pounds (140-180 kg) and measures between 5.5 and 8 feet in length, with males being larger than females.
- In 1865, Smithsonian mammalogist Theodore Nicholas Gill named the Pacific white-sided dolphin. They have very distinct markings that distinguish them from other dolphin species. It has the same morphology as the dusky dolphin, which lives in the South Pacific.
- Though traditionally assigned to the genus Lagenorhynchus, molecular analyses show that they are more closely related to dolphins in the Lissodelphininae subfamily than to both the Atlantic white-sided dolphin and the White-beaked dolphin. The Pacific white-sided dolphin, along with other southern hemispheres Lagenorhynchus species (hourglass dolphin, Dusky dolphin, and Peale’s dolphin), has thus been proposed to be moved to the resurrected genus Sagmatias.
GEOGRAPHIC RANGE AND HABITAT
- Pacific white-sided dolphins are pelagic, meaning they populate in the open ocean and coastal waters. They are most commonly seen in the cool to temperate waters of the North Pacific and neighboring seas. They prefer deep, offshore waters around the continental shelf but occasionally venture closer to shore.
- They can be seen off the west coast of North America, from California to Alaska, and their habitat includes the southern Bering Sea, the Sea of Japan, and the Sea of Okhotsk.
- The dolphins appear to follow a migratory pattern; on the eastern side, they are most abundant in Southern California during the winter but further north (Oregon, Washington) during the summer.
- Pacific white-sided dolphins swim in big groups, approximately ten to one hundred. They move fast, usually leaping out of the air. They are quick swimmers that are also quite lively and acrobatic.
- These dolphins are also highly social and playful marine mammals that keep close company. They are frequently seen bow-riding and performing somersaults. Young dolphins communicate with adults by touching their flippers together. This species has also been observed approaching boats to bow, ride or ride in the boat wake.
- These gregarious cetaceans are frequently seen with other marine mammals, most notably the northern right whale dolphin.
- The Pacific white-sided dolphin feeds on a variety of prey, including small schooling fish like anchovies and hake, salmon species, shrimp, and squid.
- These dolphins appear to feed primarily on midwater concentrations of marine animals known as the “deep scattering layer.” They use cooperative foraging techniques by herding schools of fish together. Also, they are frequently spotted eating with gulls on little surfacing balls of unidentifiable bait fish at dawn and dusk.
- They have small conical teeth that help to catch and hold prey; each tooth row contains 23 to 36 pairs of teeth, and they have an average of 60 teeth. Dolphins use their teeth to grasp food before swallowing it whole—head first—to prevent the spines of the fish from catching in their throats.
- To catch prey, they stay underwater for more than 6 minutes. Every adult can consume approximately 20 pounds of food per day.
REPRODUCTION AND LIFE EXPECTANCY
- Female Pacific white-sided dolphins attain sexual maturity at around eight, while males become sexually mature at approximately ten years old. They have a polygynous mating system which usually takes place in the spring and fall, with births happening in the spring and summer after a 9–12 month gestation period.
- Females typically reproduce every 3–5 years. Pacific white-sided dolphin life expectancy is in the range of 37–46 years old. However, the maximum age recorded for a female dolphin is 46, while the oldest male recorded is 42.
PREDATORS AND THREATS
- Transient killer whales, which devour marine mammals, are the largest predator of Pacific white-sided dolphins. Large shark species prey on them in some areas of their range.
- In the past decades, thousands of Pacific white-sided dolphins were killed due to bycatch in drift and gill nets, as well as hunting. Thus, entanglement in fishing gear is one of the most severe threats to these species. Commercial fishing gear such as gillnets, seines, trawls, trap pots, and longlines can entangle or capture dolphins.
- Prey depletion, marine debris, and the ongoing effects of climate change pose threats to Pacific white-sided dolphins.
OTHER INTERESTING FACTS
- Pacific white-sided dolphins are often confused with common dolphins and Dall’s porpoises because of their similar large light-colored flank patches.
- Usually, Pacific white-sided dolphins are bigger than dusky dolphins. However, they share many of the same physical characteristics.
- Pacific white-sided dolphins are said to be naturally acrobatic. They are considered a treat for wildlife watchers and often interact with boats.
- They can also easily be trained as oceanarium performers and become part of human entertainment.
- Japanese fishermen hunt the Pacific white-sided dolphins for their meat. They are also seen as significant contributors to the entertainment and tourism industry. For example, these dolphins are trained in marine mammal parks to perform tricks and are also used to educate attendees about dolphins.
- Pacific white-sided dolphins were observed swimming in formation with other dolphins and sea lions, occasionally doing somersaults over splashing water.
- The Marine Mammal Protection Act protects Pacific white-sided dolphins, although they are not categorized as threatened or endangered.
Pacific White-sided Dolphin Worksheets
This fantastic bundle includes everything you need to know about the Pacific White-sided Dolphin across 28 in-depth pages. These ready-to-use worksheets are perfect for teaching kids about the Pacific White-sided Dolphin, a marine mammal found in the northern Pacific Ocean and known for its energetic and acrobatic behaviors, often leaping and flipping out of the water.
Complete List of Included Worksheets
Below is a list of all the worksheets included in this document.
- Pacific White-sided Dolphin Facts
- K-W-L Chart
- Facts About Me
- Bubble Map
- Guess the Category
- Sea of Words
- A Hungry Dolphin
- Color the Emoji!
- Together, We Can!
- Bring Me Back!
Frequently Asked Questions
What is a Pacific White-sided Dolphin?
The Pacific White-sided Dolphin (Lagenorhynchus obliquidens) is a marine mammal found in the North Pacific Ocean. They are known for their distinct coloration, which includes a dark gray or black back, white or gray sides, and a white belly. They are a type of oceanic dolphin and are closely related to other species such as the Dall’s porpoise and the common dolphin.
What is the size and weight of a Pacific White-sided Dolphin?
Pacific White-sided dolphins can reach a length of about 2-2.5 m (6.5-8 ft) and weigh around 200-300 kg (440-660 lb).
What is the habitat of Pacific White-sided Dolphins?
Pacific White-sided dolphins are found in the North Pacific Ocean, from the Gulf of Alaska to Southern California and Baja California, Mexico. They are typically found in cool and temperate waters, including offshore waters and near the coast. They are also known to be found in areas with strong currents and deep waters.
What do Pacific White-sided dolphins eat?
Pacific White-sided dolphins are opportunistic feeders, and their diet includes a variety of fish, squid, and crustaceans. They are known to feed on anchovies, sardines, herring, squid, octopus and other small fish.
Are Pacific White-sided Dolphin endangered?
The Pacific White-sided Dolphin is considered a “Least Concern” species by the International Union for Conservation of Nature (IUCN) as their population is considered to be stable. However, some populations may be at risk from certain human activities such as pollution, overfishing, and accidental bycatch.
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Use With Any Curriculum
These worksheets have been specifically designed for use with any international curriculum. You can use these worksheets as-is, or edit them using Google Slides to make them more specific to your own student ability levels and curriculum standards.