Haggan: Green Sea Turtle
Description and Status
| Scientific Name | Chelonia Mydas |
|---|---|
| Common Name | Green Sea Turtle |
| CHamoru Name | Haggan or Haggan Bedti |
Green sea turtles were once a common species of sea turtles found in Guam’s waters. They can still be seen around the island where rich seagrass beds are found, including channel areas, harbors, lagoons. They can also be found foraging for seagrass and marine algae in shallow reef areas. This diet of mainly seagrass and algae is what gives them their name. Their diet makes their fat and cartilage a greenish color.
An endangered and threatened species
Before becoming a protected species, green sea turtles were being harvested and traded around the world for their skin, shell, and meat. There was concern among many different countries that over harvesting was occurring and green sea turtles were becoming endangered. For this reason green sea turtles began to be protected by different governments and countries. In the United States, green sea turtles were first protected in 1978 when they were listed as an endangered species under the Endangered Species Act.
A year later, the Endangered Species Act of Guam was passed and green sea turtles were given full legal protection at the local and Federal levels. The Federal and Guam Endangered Species Acts state that it is illegal to take a species, which means it is illegal to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect or attempt to engage in any such conduct with a listed species. This includes the buying, selling, or transporting of sea turtles or any part of the turtles including eggs, shell, shell jewelry, and meat.
There is also an international agreement between many governments called the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as CITES, that lists green sea turtles under Appendix I, which means that no trade of these species is allowed between countries except under specific circumstances and with a permit. Green sea turtles were added to this list in 1981. Prior to these laws being passed, there were no legal regulations controlling the taking of green sea turtles on Guam.
Appearance
Green sea turtles can grow to approximately 1.2 meters (four feet) in shell length and can weigh up to approximately 159 kilograms (350 pounds). Being marine reptiles, green sea turtles have slow growth rates. In the wild, green sea turtles grow approximately 1 centimeter (0.4 inches) per year until maturity, then 0.5 centimeters (0.2 inches) after. Green sea turtles reach maturity sometime between 25 and 35 years old, and can live to be more than 70 years old.
Characteristics of the green sea turtle include a pair of prefrontal scales between their eyes, a single claw on each front flipper, fused shell plates on the carapace, and rounded edges on the carapace. Their carapace, or top shell, are usually dark brown in color while their plastron, or their underside, is light yellow.
Lifespan and reproduction
The start of sexual maturity is believed to be between 25-35 years of age, usually once their carapace (back shell) reaches a length of about 80 centimeters (~32 inches). An adult male sea turtle has a longer, thicker tail than an adult female. This is one of the few ways to visually tell the difference between adult males and females. This species of sea turtle can deposit between 40 to 140 eggs in a single clutch (nest) depending on the size of the female and the amount of eggs she can contain. A nesting female can lay as many as 10 clutches in one season. However, she only nests every two to five years, but always returns to the same beach where she hatched.
The incubation period of the eggs ranges from 50 to 70 days and is dependent on the temperature of the sand where the eggs are laid. Temperature also plays an important role in the determination of the hatchlings’ sex. Similar to other reptiles, the sex of the hatchlings is decided by how hot or cold the nest is while the eggs are incubating. Ideally, the temperature inside the nest will allow for about half of the hatchlings to be male and the other half to be female. However, if the nest is too hot, there will be more females. And if the nest is too cold, there will be more males.
The hatchlings, usually five centimeters (two inches) in length, crawl up from the inside of the sandy mound towards the top of the nest and generally emerge in the evening. It may take as long as two days to complete the process of hatching.
Once hatched, the hatchlings head towards the ocean and feed on marine vegetations such as saragassum (seaweed) and other algae while adrift. The hatchlings then spend a few years drifting within ocean currents, growing slowly before settling in a foraging ground as a juvenile sea turtle.
The majority of green sea turtles seen in Guam’s waters are juveniles. Juveniles will then stay in their foraging area until they reach sexual maturity. Adult turtles will then migrate to breeding grounds. Females, in particular, will travel to breeding grounds near the beach where she hatched. Once they are done breeding and females are done nesting, they return to their foraging grounds.
Species management
The Government of Guam Department of Agriculture’s Division of Aquatic & Wildlife Resources (DAWR) is responsible for performing baseline population studies on the sea turtles. DAWR’s Guam Sea Turtle Recovery Program focuses on monitoring and helping to increase the local sea turtle population. One aspect of this program occurs in collaboration with the National Oceanic Atmospheric Administration (NOAA) and the United States Navy. This collaborative work includes tracking sea turtles by attaching satellite tags to their carapace in order to learn more about where sea turtles spend their time. The satellite tags are able to show what areas around Guam are most used or frequently visited by sea turtles.
Another aspect of the program is the volunteer Haggan Watch program. It was created in 2005 to minimize the threats to sea turtles and enhance successful nesting events by having volunteers sit on the beach and keep a protective eye on the turtles as they nest. The Haggan Watch volunteer program has evolved to include volunteers who patrol different beaches around the island looking for signs of sea turtle nesting. This allows DAWR staff to identify nesting beaches and helps to keep the sea turtle nests safe from predators and illegal hunters.
Since the Guam Sea Turtle Recovery Program began in 2000, more than 40 juvenile sea turtles and more than 10 adult female nesting green sea turtles have been intercepted, tagged, and released. The first turtle to be tagged in this program was an adult female green sea turtle spotted crawling on the beach on Andersen Air Force Base in June 2000. A team of military and local biologists named the turtle Pati, measured it, tagged it and then let it go. Pati’s shell measured 110 centimeters (more than three and a half feet) in length. She was tracked swimming to the Sulu Archipelago, Philippines. Pati was last heard from in Kulisi-An, Pangutaran, Province of Tawi-Tawi, south, within the Sulu Sea, in an area called the Turtle Islands. These islands are important feeding areas for green sea turtles.
The most recent turtle was tagged in November 2020. She was 87.5 cm (less than three feet) in length but had a very rounded carapace and therefore given the name Quaismodo. Her most recent location was noted to be around the same area as Pati, in the Sulu Sea between the Philippine Islands and Indonesia and Malaysia.
Although DAWR has yet to see Pati again, other tagged nesters have returned multiple times. Turtles face many hurdles while migrating such as drift nets, ghost nets, plastic debris, sharks, and hunters in places where catching turtles is not prohibited.
Historical significance
Green sea turtles have had an intricate historic role in CHamoru culture and diet. Turtle was traditionally eaten at feasts in the past, including weddings, funerals and other ceremonial events. Both the meat and eggs were served as delicacies.
CHamorus used turtle shells to craft jewelry including bracelets, necklaces, and pendants. Turtle shells were also used to make children’s wealth called guinahan fama’guon which was worn as a necklace.
Turtle bones were traditionally used to make tools as well.
Current threats
Predators for turtle eggs and hatchlings on the shore include crabs, rodents, monitor lizards (hilitai), birds, wild pigs, deer, stray cats, and dogs. Use of vehicles on the seashore creates an additional threat to eggs and hatchlings. Driving on the beach can compress the mound that sits on top of the nest which can make it harder for hatchlings to reach the surface. Tire tracks can also create a barrier or divot between the nest and the ocean, possibly trapping the hatchlings and creating more obstacles between the nest and the ocean. Litter on the shore can also be a threat as it gets worked into the nest by the female as she covers the nest.
Other threats to green sea turtles are habitat loss as the island becomes more populated, erosion to beaches where nests are laid, as well as climate change, not only affecting the temperature of the nest but also increasing water levels..
Once in the ocean, hatchlings may succumb to predators such as fish, octopus, sharks, birds, and crabs. Additional threats include debris such as balloons, plastic bags, and other non biodegradable items that can be ingested by the sea turtle causing respiratory complications or digestive complications. Drifting ropes and nets can entangle a sea turtle reducing their mobility and possibly resulting in drowning.
The migration route of green sea turtles is also a cause of concern because the area where the sea turtle migrates into is an area where the harvest of the species is legal and or acceptable. This harvesting is expected to contribute to the decline of the sea turtles on Guam and the region.
By Shawn Wusstig
Haggan Watch Volunteer Project Supervisor
Guam Sea Turtle Recovery Program,
Division of Aquatic and Wildlife Resources, Department of Agriculture, Government of Guam
Updated in February 2021 by CJ Cayanan
Biologist at Guam Department of Agriculture, Division of Aquatic and Wildlife Resources
For further reading
Guam Department of Agriculture Division of Aquatic and Wildlife Resources. Annual Report 2002 Government of Guam Department of Agriculture. Mangilao: DAWR, 2002.
–––. Annual Report 2007 Government of Guam Department of Agriculture. Mangilao: DAWR, 2007.
Sams, Laura, and Robert Sams directors. My Haggan Dream. Sisbro Studios and Open Boat Films. Streamed live in 2016. Vimeo video, 8:15.
The Japan Times. “Green sea turtle migrates over 2,000 km from Guam to Okinawa,” 9 May 2008.
US Department of Commerce National Oceanic and Atmospheric Administration National Marine Fisheries Service. Subsistence Use of Sea Turtles at Pacific Islands Under the Jurisdiction of the United States. By George H. Balazs. Administrative Report H-83-17. Honolulu: SFC, 1983.
Weekly Japan Update. “Pacific Traveling Sea Turtle Tracked to Kume Island,” 16 May 2008.
Resources for teachers
Below are some websites featuring educators’ guides that teachers can use in classrooms for lessons on turtle conservation:
- NOAA Pacific Islands Fisheries Science Center
- The Archie Carr Center for Sea Turtle Research
- Seaturtle.org
- South Pacific Regional Environmental Programme
- Turtle Trax
Other resources can be found by visiting the following organizations’ websites: