Honu--The Hawaiian Green Sea Turtle

We have seen honu many times. Yesterday, when it was turbulent, I almosts swam into him. I was swimming towards him. Rich pulled me back. Then we just watched him, but because of the currents, had to keep pulling away as the current was washing us towards him/her.

Video of honu eating at Kahalu'u 
honu eating breaksfast

The green turtle is listed as endangered by the International Union for the Conservation of Nature. In 1978, the Hawaiian population of the green turtle was listed as threatened under the U.S. Endangered Species Act of 1973.

honu swimming
Green turtles were a source of food, tools, and ornamentation for early Hawaiians. With the arrival of western culture, however, the level of exploitation of this resource increased dramatically. Large numbers of green turtles were harvested throughout the Hawaiian Islands through the nineteenth and early twentieth centuries. In 1974, the State of Hawaii finally passed a regulation providing some protection, but this was virtually ignored until 1978, when the Hawaiian green turtle was placed on the list of threatened species.

 Fortunately, over 90% of nesting activity for the Hawaiian green turtle population occurs at the French Frigate Shoals, inside a National Wildlife Refuge System administered by the U.S. Fish and Wildlife Service. This, combined with its threatened status under the U.S. Endangered Species Act, has created an environment in which the Hawaiian green turtle should prosper. 

The green sea turtle is the largest hard-shelled sea turtle. Adults of this species commonly reach 100 cm in carapace length and 150 kg in mass. The average size of a female nesting at the French Frigate Shoals was reported in 1980 to be 92 cm straight carapace length, with an average body mass of 115 kg. This is somewhat smaller than her Atlantic cousin.

Based on growth rate measurements, George Balazs estimates the age of the Hawaiian green turtle at sexual maturity can range from 11 to 59 years. (Yes, 59 years!)
Hawaiian green turtles occupy three habitat types:

• Nesting and basking beaches, almost exclusively in the French Frigate Shoals.
• Convergence zones in the pelagic habitat.
• Benthic feeding grounds in relatively shallow waters.

Females deposit egg clutches on beaches in the French Frigate Shoals, digging a deep nest cavity above the high water line. Eggs incubate for approximately 65 days before hatching. Hatchlings leave the beach and apparently move into convergence zones in the open ocean where they spend an undetermined length of time. Hawaiian green turtles reach a carapace length of approximately 35 cm, about 10 cm larger than juveniles of other green turtle populations, before leaving the pelagic habitat and entering benthic feeding grounds.

One interesting behaviour of the Hawaiian green turtle is its fondness for crawling ashore at isolated sites in order to bask. Basking is rare among marine turtles, and has been observed in only a few populations in the Pacific. Hawaiian green turtles bask, but this behaviour seems to be limited to the Northwestern Hawaiian Islands. It is thought that they do this for thermoregulation (they like to warm up in the sun), resting (they like to sleep in the sun), and perhaps for protection from tiger sharks (they don't like to be eaten). Sounds just like people to us.

 While Hawaiian greens are primarily vegetarians, it is clear that they aren't fanatics about it.
Female green turtles emerge at night to deposit eggs, the process taking an average of two hours. Up to seven clutches are deposited at 12 to 14 day intervals, but the average is probably two or three clutches. Accurate counts of the number of clutches per season are difficult to get. The average clutch size is 100-110 eggs.

The Hawaiian green turtle enjoys the benefits of a protected and isolated nesting habitat and low levels of predation. Unlike many nesting areas throughout the world, there are no nest-raiding predators (not even humans) in the French Frigate Shoals. Ghost crabs prey upon hatchlings, but estimates of losses to crabs do not exceed 5%. Unlike other nesting beaches throughout the world, hatchlings are not greeted by predatory birds, and the loss to carnivorous fishes does not appear to be significant. Hatchlings in the French Frigate Shoals do not suffer from human interference either; there are no distracting lights from developments and no destructive beach activities.

Hawaiian green turtles nest in the isolated French Frigate Shoals, but forage throughout the entire Hawaiian Archipelago, a range of 2450 km. Tagging has indicated that most Hawaiian green turtles seem to settle at a specific foraging ground and leave only to reproduce. 

• Found throughout the Hawaiian Archipelago, a range of about 2450 km
• A gentle vegetarian, feeding almost exclusively on algae
• The most valuable of all reptiles, they were once killed for their skins, calipee, meat and shells, but are no longer hunted in Hawaii
• In parts of Hawaii (Honokowai) more than 90% of the green sea turtles are afflicted with fibropapilloma tumors
• The largest of the hard-shelled marine turtles: common adult weight of 115 kg and length of over 90 cm
• Hatchlings: 4-5 cm in length