B.C. Reptiles & Amphibians

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Credit: Jim Trodel

Green Sea Turtle

Chelonia mydas

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Description

The Green Sea Turtle is a large, solitary, marine turtle species that is very rare in the Pacific waters of Canada. They are the largest of the hard-shelled turtles and may reach lengths of up to 1.5 m, and may weigh up to 315 kg, although most individuals are smaller and lighter than this. The carapace is mildly heart-shaped, lightly serrated at the back, and has variable colouration that can change over time ranging from green, brown, grey, black, and yellow. The plaston on the underside is a pale yellow. The skin of the turtle is olive-green to dark brown, while the underside of the head, limbs, and tail are creamy-white to yellow. The head is beaked but unhooked with a short neck and snout. The limbs are modified for life in marine environments and are paddle-shaped, with males having a single curved claw on their front flippers that is much larger than in females.

Listen to the Indigenous words for “turtle” here!

Similar Species

In Canada, the Green Sea Turtle may be confused with the Pacific Leatherback Sea Turtle or the Olive Ridley Sea Turtle, although all sea turtle species are accidental in Canada and are generally very rare. The Pacific Leatherback Sea Turtle has no scutes on the shell, but is instead leathery and lacks the bright colouration of the Green Sea Turtle. The Olive Ridley Sea Turtle may be coloured similarly to the Green Sea Turtle, but they are generally much smaller and have 6 or more costal scutes, whereas Green Sea Turtles usually have 4.

Pacific Leatherback Sea Turtle

Green Sea Turtle

Olive Ridley Sea Turtle

Distribution

The Green Sea Turtle is a highly migratory species with a circum-global distribution. They are primarily found in the tropical waters and subtropical waters of the Atlantic Ocean, Indian Ocean, Mediterranean Sea, and Pacific Ocean. It is found in the coastal waters of over 180 countries and nests in more than 80 of these countries. In the Pacific, it ranges from southern Alaska to Chile. Green Sea Turtles are primarily tropical, but periodically will follow warm currents up to British Columbia and Alaska. Green Sea Turtles are considered accidental in British Columbia, as the waters are generally too cold for long-term survival. There are few records of Green Sea Turtles in British Columbia, and many of them have occurred recently, leading many biologists to assume that Green Sea Turtles may be more common in B.C. waters than previously thought. Green Sea Turtles are at risk of global extinction, thus, information on distribution and population sizes is very important. If you see a Sea Turtle report your sightings!

British Columbia Cetacean and Sea Turtle Sightings Network (BCCSN)
1-866-I SAW ONE (1-866-472-9663)

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Habitat

Throughout their lifetimes Green Sea Turtles use a wide range of habitats and cover vast distances, from sandy beaches and coral atolls for nesting, to eelgrass and kelp beds for feedings, to open ocean currents for migration. Almost immediately after hatching, Green Sea Turtles leave their sandy nesting beaches and head to the open ocean where they are thought to undergo much of their development. After a number of years in this ‘developmental zone’ in the deep oceans, they return to the shallower waters of the continental shelf that are rich in seagrass and algae where they forage until mature. Once sexual maturity is reached, Green Sea Turtles will make breeding migrations between foraging grounds and nesting areas every few years that often span across oceanic zones and may end up being thousands of kilometers long. However, many individuals will settle in foraging areas that are close to their breeding/nesting habitat.

Reproduction

Courtship among Green Sea Turtles can often be a long, arduous affair. Females only mate every 2-4 years, leading to competition amongst males for breeding rights. Males will court a female for several hours, while competing with other interested males, before the female chooses her mate. Mating occurs either at the surface, or on the seafloor and can often last many hours. Females will only mate once per season, and as such, one male will have fertilized all of the eggs she lays for that year. Green Sea Turtles will often return to the same beach where they hatched, sometimes swimming distances of 2,600 kilometers or more to reach their spawning grounds. Females will lay 2-5 clutches, spaced 9-15 days apart, of 80-120 ping-pong ball sized eggs above the high tide line on sandy beaches or coral atolls by excavating a nest cavity in the sand. Hatching occurs approximately 2 months later at night, and the newborn turtles immediately head to the sea. Green Sea Turtles do not reach sexual maturity until 20-40 years of age, and most live for over 60 years.

Diet

Adult Green Sea Turtles are obligate herbivores and feed almost exclusively on seagrasses and algae. Juveniles on the other hand, are primarily carnivorous and eat many small animals including sponges, corals, jellyfish, bivalves, and crustaceans.

Conservation Status

Global: G3 (2014)

Provincial: SNA (2018)

BC List: Accidental

Learn more about conservation status rankings here

Threats

The Green Sea Turtle is globally threatened according to the IUCN due to extensive declines in all major ocean basins over the last 3 generations, following overexploitation of eggs and adult females at nesting beaches, juveniles and adults in foraging areas, and incidental mortality from marine fisheries. Historically Green Sea Turtles were highly sought after for their body fat and eggs. Although it is illegal to harvest and trade Green Sea Turtles in many parts of the world, they are still consumed and considered a delicacy. A rising concern for Green SeaTurtles is the accumulation of plastics and marine debris that may be ingested by turtles, causing death or serious injury. Climate change may also impact Green Sea Turtle populations through major habitat changes and by shifting sex ratios due to changing nest incubation temperatures.
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Did You Know?

Fact #1

Most Green Sea Turtles do not hibernate, however, a few off the coast of California have been observed spending extended periods in the muddy sediments at the bottom of the ocean. Green Sea Turtles can remain below the surface of the water for up to 5 hours while foraging before coming up for air.

Fact #2

It is possible to differentiate male and female Green Sea Turtles by their tails. Females have short tails, while males have long tails with a horny tip.

Fact #3

The sex of neonatal sea turtles is temperature dependent. If the temperature of the nest is 28°C or cooler, primarily males are produced. If the temperature of the nest is 30°C and higher, almost exclusively females are produced. When temperatures fall in between, clutches are often mixed evenly with both sexes.

Species Account Author: Marcus Atkins

References

B.C. Conservation Data Centre. 2009. Species Summary: Chelonia mydas. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 22, 2021). 
B.C. Conservation Data Centre. 2021. BC Species and Ecosystems Explorer. B.C. Minist. of Environ. Victoria, B.C. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 22, 2021).  
http://canadianherpetology.ca/species/species_page.html?cname=Green%20Sea%20Turtle 
http://linnet.geog.ubc.ca/efauna/Atlas/Atlas.aspx?sciname=Chelonia%20mydas 
https://www.bcreptiles.ca/turtles/pacificgreen.htm