The Hawaiian Green Sea Turtle and Marine Debris

Green Sea Turtle

Scientific name: Chelonia mydas

Pacific Island names: honu (Hawaiian), haagan (Chamorran) laumei ena'ena (Samoan)

Stock Assessment / Estimated Breeding Population

Despite an overall declining trend globally, green turtle population growth rates are variable among nesting populations and regions. The Hawaiian green turtle population is actually increasing in abundance and has increased 53% over the last 25 years. Low levels of green turtle nesting also occur in Guam, American Samoa, the Northern Mariana Islands, and other U.S. island territories. Information on population trends for green turtles in the region other than the Hawaiian stock is limited.

Legal Protection

• Endangered Species Act (ESA)

• Hawaii state law

Natural History

Green turtles are found throughout the world, occurring primarily in tropical, and to a lesser extent, 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 because of direct harvest of both turtles and eggs by humans. The population has grown steadily over the last thirty years after protection began in 1978. Greens are the most common species of sea turtle found in Hawaiian waters.

Physical Description

• A typical adult green turtle has a carapace length of 40 inches and can weigh from 200-500 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. (Unlike the hawksbill turtle which has the same number of scutes, the scutes of the green turtle do not overlap).

• Another distinguishing characteristic of this species is their two large prefrontal scales located between the eyes.

Diet

Adults primarily eat algae. Over 275 different species of seaweed have been found in the stomachs of Hawaiian green turtles. In order to deal with this diet of roughage, green turtles have microflora living in their large intestine that help breakdown the cellulose that is otherwise undigestible. Other food items they consume in lesser amounts include jellyfish, salps, mollusks, sponges, and tubeworms. East Pacific green turtles tend to eat more animal prey than other populations.

Lifespan

The lifespan for sea turtles in generally unknown but for green turtles is thought to be around 60-70 years.

Reproduction

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

The length of reproductivity has been estimated to range from 17 to 23 years.

They return to nesting beaches to lay eggs every two to three years and will deposit three to six clutches per nesting season with an average of twelve days in between. Each clutch consists of about 100 eggs that will incubate for 60 days.

Distribution

More than 90% of the Hawaiian population of green turtles nests at French Frigate Shoals in the Northwestern Hawaiian Islands. They migrate to feed mainly in the coastal areas of the Main Hawaiian Islands. Limited nesting locations and important coastal foraging areas for green turtles are found throughout the Pacific islands.

Local Cultural Significance

Historically, green turtles have played a large role in Polynesian and Micronesian cultures. In addition to being used as a food source, native peoples all over the Pacific utilized all parts of the turtle making tools and jewelry out of the bones, and containers and utensils out of the carapace. Turtle fat was sometimes used for medicinal purposes to treat burns and other skin disorders. Turtles were often considered the property of the tribal chief and their utilization was regulated by some form of island council.

In the Hawaiian Islands, there were families that considered the green turtle a personal family deity or aumakua, not to be eaten or harmed. One legendary example is the story 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 some cultures of the region, such as petroglyphs and tattoo designs.

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