Protected Resources

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Green Sea Turtle

Rachel O'Shea ©SPC

Scientific name: Chelonia mydas
Pacific Island names: honu (Hawaiian), haagan (Chamorran), laumei ena'ena (Samoan)

Stock Assessment / Estimated Breeding Population

Green sea turtles have circumglobal distribution occurring primarily in tropical and subtropical waters. Green turtles nest in over 80 countries and inhabit coastal waters of over 140 countries. While green turtle nesting dynamics can be variable among nesting populations and regions over time, recent data suggests that primary nesting locations, or index sites, are stabilizing and in some cases increasing. This is the case for the Hawaiian green turtle population which has experienced an increasing nesting population trend of 5% per year over the last two decades. In NOAA’s Pacific Islands Region, green turtle nesting also occurs in Guam, American Samoa, the Commonwealth of the Northern Mariana Islands (CNMI). However, nesting trends in these areas are currently unknown as populations continue to face threats from human take (harvest).

Legal Protection

Viewing Guidelines

View turtles from a respectful distance of 10 feet (3 meters).

  • Human disturbance can disrupt normal behavior and cause stress. Do not attempt to touch, feed, chase, or harass sea turtles.

Never feed directly or indirectly

  • Never feed, and do not unintentionally feed turtles when cleaning fish at harbors or from your boat as this may increase their risk of fishery interaction or boat strike.

Boaters, Post-a-Watch!

  • Prevent boat strikes by looking out (posting a watch) for marine wildlife. Ensure “turtle safe” transit (5-10 knots) near harbors and when driving over shallow reef habitats.

Accidental interactions in shore-based fisheries

Contact Information

  • To report a dead or injured sea turtles or marine wildlife emergencies, please call: (888) 256-9840. This is a new state-wide menu based number for monk seals, sea turtles, whales and dolphins.
  • Non-emergency inquiries can also be sent to RespectWildlife@noaa.gov

Natural History

Green turtles are found throughout the world, occurring primarily in tropical and subtropical waters. The Hawaiian green turtle is genetically distinct from the other green sea turtle populations, nesting primarily in the French Frigate Shoals of the Northwestern Hawaiian Islands and feeding in the coastal areas of the main Hawaiian Islands. This species was in a steep decline as of the 1970s due to subsistence and commercial harvest of both turtles and eggs by humans. As a result of State and federal (ESA) protections over the past thirty years, the nesting population has responded positively, increasing at a rate of 5% per year, with almost 800 females nesting annually (compared to 67 turtles in 1973). Greens are the most common species of sea turtle found in Hawaiian waters.

Physical Description

  • Primary distinguishing characteristic of this species is their 2 large prefrontal scales located between the eyes, in contrast to hawksbill turtles that have 4 scales (or two pairs) of prefontral scales.
  • A mature adult green turtle has a carapace length of approximately 3 feet (36 inches or 90 cm) and can weigh around 350 lbs.
  • Green turtles exhibit counter-shading with a carapace (shell) that can range from olive brown to black in color and a much lighter yellow plastron (underside).
  • Green turtles have five vertebral scutes running down the middle of their shell and four costal scutes on each side. Green turtle scutes do not overlap but are adjoining (like tiles).

Diet

Green turtles living in nearshore reef habitats of Hawaii primarily eat red and green algae or seaweed (locally known as limu). Of approximately 400 species of seaweed present in the Hawaiian archipelago, nine species account for the majority of green turtle diet. A study of 181 green turtles from various areas of Hawai'i found that the non-native red algae Cladophora sp. was the most common item in their diet. This research helps confirm that turtles are selective feeders, and prefer certain types of seaweed. Further, green turtles predominately eat invasive seaweeds introduced to Hawai'i during the 1950s, which have stifled some reefs (such as those in Kaneohe Bay) for many years. Other food items they consume in lesser amounts include jellyfish, salps, mollusks, sponges, and tubeworms. Green turtles are beneficial and necessary components to a healthy and productive Hawaiian reef ecosystem.

Lifespan

The lifespan for sea turtles in generally unknown but for green turtles is thought to be around 70-80 years.

Reproduction

Photo: Mating Hawaiian green sea turtles. Dr. Malia Rivera

Green turtles become sexually mature between 25-35 years of age, and some may be as old as 40 before being able to reproduce.

The length of reproductivity is unknown since we’ve only been studying this population for 44 years, but one turtle has been known to nest for 38 years.

Green turtle return to the same nesting beach where they themselves hatched to lay eggs every three to four years. They deposit an average of four nests (clutches) per nesting season with each nest about twelve days apart. Each clutch consists of about 100 eggs that will incubate for 60 days.

The incubation temperature of the nest determines a hatchling’s sex: warmer nests produce females, and cooler nests produce males. Hatchlings typically emerge from the nest at night and find the ocean by crawling towards the brighter, open horizon.

Distribution

Photo: Hawaiian green sea turtle hatchlings emerge from a nest on Tern Island in the French Frigate Shoals.

Approximately 96% of the Hawaiian population of green turtles nests at French Frigate Shoals in the Northwestern Hawaiian Islands, a 1,200 mile round trip migration from coastal foraging habitats of the Main Hawaiian Islands. The Hawaii population of green turtles occurs only within the Hawaiian Archipelago and does not undergo international migrations. In contrast, other green turtle populations occurring throughout the Pacific Islands undergo long international migratory movements between nesting beach and foraging habitats. For example, green turtles nesting at Rose Atoll, American Samoa migrate to foraging habitats in Fiji and French Polynesia, and nesting green turtles of the Marianas Archipelago (Guam and Saipan) have been satellite tracked to foraging habitats of the Philippines and Japan.

Cultural Significance

Photo: Hawaiian green sea turtle at Lanikaea beach

Historically, green turtles played a large role in Polynesian, Micronesian and Melanesian cultures. As indigenous species in Hawai‘i, sea turtles play an important role in Hawaiian cultural traditions and mo‘olelo (stories).

Honu (green turtle) and ‘ea or honu‘ea (hawksbill turtle) are mentioned in the fourth verse of the Kumulipo, the Hawaiian creation chant. Some families continue to revere sea turtles as their ‘aumakua, or spiritual guardian.

Traditionally, sea turtles were incorporated into native practices, religious ceremonies, and diet. Shells, bones and oil were used to make fish hooks, tools, jewelry, and medicine. Turtles were considered the property of the tribal chief and their utilization was tightly regulated by traditional management practices of the kapu system (cultural rules, code of conduct) enacted by Chiefs or Ali‘i.

One legendary story is from the Big Island of Hawaii of the turtle named Kauila. She was believed to be able to change at will into human form to watch over the village children playing near the shore. Artistic elements of green turtles have also been featured prominently in cultures of the region, such as petroglyphs and tattoo designs.

Threats

Major threats to green turtle populations include: loss of nesting habitats; harvest of eggs and turtles; predation; disease; lack of comprehensive and consistent protective regulations in some countries; and incidental take in artisanal or commercial fisheries. Hawaii specific threats include:

  • Habitat loss – increasing temperatures and sea level rise may affect nesting and foraging habitats, alter sex ratios, and affect nesting success and hatchling survival. The primary green turtle nesting habitat is at French Frigate Shoals, NWHI which is a low-lying atoll very susceptible to erosion and habitat loss from sea level rise.
  • Bycatch – Accidental catch in shore-based fisheries is the primary threat to sea turtles in Hawaii. See the mutli-agency Fishing Around Sea Turtle program for current management options and more information on how fishermen can help to prevent deadly gear entanglement.
  • Disease – Fibropapillomatosis (FP) is a tumor-causing virus that occurs on the flippers, head, and neck areas. While the tumors do not appear to be accompanied by any other symptoms or negative effects, their location could be detrimental to the survival of an individual. For example, if a tumor obstructs a turtle's mouth or eyes enough, it may starve due to inability to locate and/or ingest food. Tumors around the eyes may also impair vision so that a turtle's ability to avoid predators is reduced. The prevalence of the disease has declined over time, but persists in the population. Unfortunately there is no cure or treatment for FP, but NOAA and partners continue to study the disease.
  • Coastal development and pollution – Beach armoring, erosion, invasive algae, and urban/agricultural runoff can damage or reduce the quality of habitats.
  • Direct “take” or harvest - In a American Samoa, Guam and the Commonwealth of the Marianas Islands, direct harvest remains a serious threat to green turtle populations. Harvest of Hawaiian green turtles is no longer a primary threat and their positive population growth is evidence of successful protection.
  • Incidental take in commercial longline fisheries [this should link to PIRO SFD management pages]

  • Disease - Disease is considered the primary threat to green turtles in Hawaii. Fibropapillomatosis causes tumor growth on the exposed soft tissue including flippers, head, and neck areas. While the tumors do not appear to be accompanied by any other symptoms or negative effects, their location could be detrimental to the survival of an individual. For example, if a tumor obstructs a turtle's mouth or eyes enough, it may starve due to inability to locate and/or ingest food. Tumors around the eyes may also impair vision so that a turtle's ability to avoid predators is reduced
  • Harvest - In a American Samoa, Guam and the Commonwealth of the Marianas Islands, direct harvest remains a serious threat to green turtle populations. Hawaiian green turtles have been successfully protected from these threats for over 25 years and their population growth is evidence of the success of such protection.
  • Incidental take in fisheries
  • Indestions of marine debris
  • Entanglement
  • Habitat loss
  • Nest and hatchling predation
  • Accidental nearshore fishery interaction - see Fishing Around Sea Turtle program web page for more information.

Current Management Issues

On February 16, 2012, NOAA Fisheries received a petition from the Association of Hawaiian Civic Clubs to classify the green sea turtle (Chelonia mydas) in Hawaii as a distinct population segment (DPS) and delist this DPS under the ESA.

On August 1, 2012, we made a positive 90-day finding (77 FR 45571), determining that the petitioned action may be warranted.

On March 23, 2015, NOAA Fisheries issued a 12-month finding and proposed rule to remove the current range-wide listing of the green sea turtle and, in its place, list eight DPSs as threatened and three DPSs as endangered (80 FR 15271). We then solicited comments on the proposal and held public hearings.

On April 6, 2016, we issued a final rule that removes the current range-wide listing of the green sea turtle and instead lists eight DPSs as threatened and three DPSs as endangered (final rule). Although we find that the Hawaiian green turtle population (referred to in the final rule as the Central North Pacific population) does constitute a DPS, we do not find that removing this population from the ESA is warranted. All green sea turtles in the Pacific Islands Region are protected by the ESA and remain protected under the final rule.

Overview of Green Sea Turtle Distinct Population Segments

Overview of Green Sea
Turtle Distinct Population Segments Map
Distinct Population Segment Nester Abundance % at Largest Nesting Site Status Under ESA

1. North Atlantic

167,528

79%

Threatened

2. Mediterranean Sea

492 25% Endangered

3. South Atlantic

63,332 46% Threatened

4. Southwest Indian

91,159 30% Threatened

5. North Indian

55,243 33% Threatened

6. East Indian / West Pacific

77,009 32% Threatened

7. Central West Pacific (includes Guam and the Commonwealth of the Northern Mariana Islands)

6,518 22% Endangered

8. Southwest Pacific

83,058 37% Threatened

9. Central South Pacific (includes Pacific Remote Island Areas and American Samoa)

2,677 36% Endangered

10. Central North Pacific* (includes Hawaii and Johnston Atoll)

3,846 96% Threatened

11. East Pacific

20,112 58% Threatened

*Subject of petition

For more information on the green sea turtle, please see the NOAA Fisheries Office of Protected Resources’ green sea turtle page

Frequently Asked Questions (FAQ) about the natural history and ecology of Hawaiian green sea turtles

Volunteer Opportunities

Malama Na Honu Program, Haleiwa, North Shore, Oahu

More Information