Green Sea Turtle Conservation
An estimated 100 to 350 female Green Sea Turtles nest each year at French Frigate Shoals in the Northwest Hawaiian Islands. Worldwide, fewer than 200,000 nesting females are thought to remain, where once there were several million. Some of the factors contributing to their decline are hunting, fishing, marine debris, and disease.
The Green Sea Turtle (Chelonia mydas) has long been hunted for their shells to make jewelry and ornaments, their skin to make leather goods, their meat and eggs for food, and their fat for oil. As a result, Hawaiian populations experienced dramatic declines, and since sea turtles take so many years to reach sexual maturity, it has taken 20 years since the passing of the Endangered species Act to see evidence of a population recovery.
Another cause of sea turtle death is from the unfortunate entanglement in longlines, driftnets, coastal gill nets and other discarded fishing gear. Commercial shrimpers use nets that trap and drown thousands of sea turtles each year. In 1992, regulations were finalized to require turtle excluder devices (TEDs), that keep turtles out of the nets.
Marine debris can prove deadly when sea turtles get entangle or they ingested it. Ingested plastics can clog the turtle’s digestive system and release toxic substances, causing them to starve or be poisoned. An infectious disease known as fibropapilloma is also a problem in Hawaii’s population. Fibropapilloma causes the growth of a large bulbous tumor on their soft tissue, which often spreads to many parts of the body, ultimately leading to their death. While the exact cause of the disease is not known, scientists suspect that a virus, parasite, or the effects of marine pollution may be involved.
Green Sea Turtles in Hawaii, are fully protected under both the federal Endangered Species Act and under Hawaii state law. Government agencies have formed a recovery team to help restore Hawaii’s green sea turtle population to previous levels. The goals of the recovery team are to identify research, management, and enforcement for effective sea turtle conservation in the islands as well as promoting sea turtle protection through public education programs.
Green Sea Turtle Breeding
Even though millions of years of evolution have fully adapted the Green Sea Turtle to marine life, they depend on land to complete the most critical stage of their life cycle – reproduction. Besides basking in the sun, male sea turtles rarely leave the water, and female sea turtles leave the ocean only to lay eggs every 2 to 3 years.
Green Sea Turtles (Chelonia mydas) migrate long distances between their natal beaches and their feeding sites and back again. Hawaii’s turtles migrate between 800 and 1,400 miles from their feeding areas along the coasts of the main Hawaiian islands to their nesting beaches in the Northwestern Hawaiian islands. Males accompany the females during the migration in the late spring, and mate with them off the shores of the nesting beaches. The most popular nesting beaches are on French Frigate Shoals, where an estimated 90% of the Hawaiian population of green sea turtles mate and lay their eggs at the same exact beach where they hatched.
After mating in the water, females haul themselves onto the beach above the high tide line, and dig a hole with her hind flippers. The number of eggs laid per litter range between 100 to 150 eggs, each one about the size of a ping-pong ball. After laying eggs, the female then covers the nest with sand, tamps down the sand with her plastron, and flings more sand about with her flippers to camouflage any signs of the nest. They also have been observed digging another “decoy nest” next to the real one to deceive predators and keep their eggs safe. Her parenting job completed, she returns to the sea, leaving her young to fend for themselves.
Green Sea Turtle
Green Sea Turtles (honu) are so ancient they watched the dinosaurs evolve and become extinct. These fascinating creatures have played an important role in the culture of the Hawaiian people. Ninety percent of honu mate and lay eggs on French Frigate Shoals, and travel hundreds of miles to the main islands in search of food and adventure, and then return to their natal beach to breed. It is between these long journeys that we have the good fortune of enjoying their visits along the coasts of the main Hawaiian Islands. This is where they spend most of the 80 or more years of their life feeding on algae and sea grasses.
Green Sea Turtles (Chelonia mydas) primarily occupy three types of habitat: ocean beaches for basking and nesting, convergence zones in the open ocean, and benthic feeding grounds in coastal areas. Honu get their name from the color of their body fat, which is green from the algae (limu) they eat. Adult Green Sea Turtles are herbivores feeding on various species of algae, sea grass, and seaweed. They spend most of their time in coastal waters and lagoons with lush seagrass beds. Juveniles, on the other hand, are carnivorous and feed on jellyfish, crustaceans, and other invertebrates. After emerging from the nest, hatchlings swim to offshore areas, where they are believed to live for several years, feeding close to the surface on a variety of pelagic plants and animals. Once the juveniles reach a certain age, they travel to nearshore coral reefs where limu is plentiful and become almost exclusively herbivores.
Because of their size and mobility in the water they have only two predators – sharks and humans. Near their nesting grounds in the Northwestern Hawaiian Islands, where tiger sharks are more plentiful, adult male and female turtles can often be seen crawling up on the beaches and laying motionless in the sun for hours. This phenomenon known as basking is believed to help the turtles avoid predation by tiger sharks and also serves to increase their body temperature and speed up their metabolism. Hawaii’s population of green sea turtles is listed as threatened under the federal Endangered Species Act.
Hawaiian Monk Seal Conservation Efforts
There is no question that human disturbances impact Hawaiian Monk Seals and their habitats. Some effects are obvious, such as when seals get tangled in fishing gear and other debris left behind by humans. But other effects of human disturbances are more difficult to measure. For example, human activity near the beaches that seals use for pupping will cause mother seals to avoid these favored spots and instead choose locations that are less safe for themselves and their pups. This choice results in a decline in pup survival rates, which in turn results in fewer adult seals giving birth generations later.
The survival rate of the pups varies dramatically from island to island and from year to year. In the 1980s, the first-year survival rate was 80 to 90 percent, but in recent years, this rate has dropped to as low as 30 percent on some islands, such as on French Frigate Shoals. The low survival rate is especially significant given that female monk seals do not bear young until they are 6 or 7 years old, have only one pup per year, and may not pup every year. At French Frigate Shoals, young monk seals are being picked off by Galapagos sharks that have been observed attacking nursing pups in as little as 2 inches of water, claiming up to 35 percent of pups born at the shoals.
Biologists are now trying to improve the survival odds of pups with two new strategies – relocation and deworming. Six weaned seals were taken from French Frigate Shoals in August and released at Nihoa Island, where sharks are not as much of a threat. And as part of a trial deworming program, several juvenile seals at Laysan Island were given the first of several doses of medication to eliminate parasites to boost their health. Because research shows that many juveniles die from emaciation, scientists believe that climate changes may have reduced the monk seal food supply at some islands. A reduced food supply means increased competition, and juveniles often do not have the skills to compete.
While other species of seals swim hundreds of miles to feed or mate, Hawaiian Monk Seals do not leave their island chain home. Because the islands are so isolated, there is no buffer. There is no place for animals to go when conditions change, such as when the food supply decreases or the number of predators increases. With new technology, including ‘critter cams’, scientists can now observe their underwater behavior. Recently, researchers have been able to witness young monk seals competing for food with other species. Their health reflects the health of the entire marine environment in which they live. Therefore, our concern needs to center on the health of the complete habitat, not just the creatures themselves.
