Hawaiian Green Sea Turtles

by B. N. Sullivan

In recognition of World Turtle Day, May 23, we have decided to tell our readers a few things about our favorite turtle species, the Hawaiian Green Sea Turtle (Chelonia mydas), known as Honu in the Hawaiian language.

Our Hawaiian Green Sea Turtle population was nearing extinction not too long ago, but thanks to Federal and State protection laws and sound conservation efforts, the Honu population is slowly beginning to recover. These days these turtles are a common sight around many of the reefs and shorelines of the main Hawaiian Islands.

Hawaii's Green Sea Turtles nest in the uninhabited Northwestern Hawaiian Islands, primarily in the area called French Frigate Shoals. Tagging studies have shown that sea turtles tend to nest once every two to five years on the same beaches where they were hatched. When they are finished mating and nesting, they migrate hundreds of miles back to the main islands, which are their foraging grounds.

More recently it also was discovered, through tagging and telemetric monitoring, that individual Green Sea Turtles tend to 'hang out' in the same foraging area for periods of years. Once they find their spot, they don't wander very far, except when the time comes to migrate again to the nesting grounds. We have anecdotal evidence of this as well. Over our years of frequent diving and beachgoing at the same places, we learned to recognize a number of individual sea turtles. We saw those individuals again and again and again within a very small range for years at a time.

Long-time readers of The Right Blue may recall our stories about a particular turtle we named Myrtle. This individual lived for years in a certain small cove along the shoreline at Puako, on the Kohala Coast of Hawaii's Big Island.

Quite a few turtles reside in that area, but we began to recognize this one particular turtle because she had a small but noticeable blemish right in the center of her carapace. That little blemish in her shell set her apart from the others and made her easy to spot.

Once we learned to recognize Myrtle, we noticed that she could be found at almost any time in the same little cove. Most often we would see her grazing on the limu (seaweed) that covered the rocks in the shallow water of that cove. In fact, she seemed to spend most of her time feeding. That's Myrtle in the second photo, foraging for limu, along with a much smaller companion (called Baby, naturally).

Occasionally we would see Myrtle out on the reef while we were diving, but there was nothing random about where we would see her: Myrtle had a favorite spot near the base of one particular coral formation. We saw her repeatedly in that exact place, being cleaned by surgeonfish, or just resting.

Myrtle also engaged in basking, a behavior peculiar to Hawaii's Green Sea Turtles. In most places around the world, sea turtles only leave the ocean and come up onto the shoreline to nest. Here in Hawaii, there are a number of locations where Honu haul themselves completely out of the water and bask in the sunlight. No one is exactly sure why Hawaiian Green Sea Turtles engage in this basking behavior. It may have something to do with temperature regulation and metabolism, or it may be a way to rest without fear of being preyed upon.

(Or could it be that, just like the thousands of tourists who spend time basking on Hawaii's beaches, the turtles are just 'working on their tans'??)

Regardless of the reason, it is not uncommon to see a number of sea turtles basking along certain shorelines any day of the week. Puako is one of those areas. The sight of sea turtles lying motionless on the rocks or sand surprises people who have never before witnessed this behavior.

As I wrote in an earlier article about Puako's tidepools and turtles:

Many newcomers and tourists become alarmed when they first spot the turtles on the beach or the rocks at Puako. They assume that the turtles somehow got stuck there as the tide receded, or that they might be injured. Sometimes it takes quite a bit of explaining to convince them that this is the natural behavior of these creatures. The basking turtles are not in distress, and they need no assistance to get back into the ocean. (Honest!)

We love our sea turtles, and we love to show them to visitors. There are some rules that must be followed, however.

Never disturb a sea turtle that is basking on the shoreline, grazing in the shallows, or resting on the reef. Don't try to touch or pet them. Don't try to feed them. And if you encounter a sea turtle while you are swimming, snorkeling or diving, PLEASE do not try to ride it!

Sea turtles are air breathing animals. They can remain underwater for a considerable amount of time, but sooner or later they have to come to the surface for air. Nothing frightens a sea turtle more than being restrained underwater. They know instinctively that this means they cannot surface to breathe. Please don't terrorize our turtles by doing anything that they might interpret as restraint.

The Honu -- Green Sea Turtle -- is the most common species of sea turtle in Hawaiian waters. Two other sea turtle species are seen here less frequently. Hawksbills (Eretmochelys imbricata) -- called Honu'ea in Hawaiian -- do visit our reefs and shorelines, but in much smaller numbers than the Honu. Leatherback sea turtles (Dermochelys coriacea) are found in our neighborhood as well, but only in the open ocean, well offshore.

The Honu photos on this page were taken at Puako, Hawaii. You can click on them for a larger view. Click here for an index to all of the sea turtle articles and photos on The Right Blue.

If you would like to learn more about Sea Turtles, we recommend the Turtle Trax website, and the Sea Turtle Restoration Project website.

UPDATE June 8, 2009: We are pleased to announce that this article was included in the 25th Carnival of the Blue, a monthly compilation of the best of ocean blogging.

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Note: Some of the information in this article was derived from the following sources:

Balazs, G.H. (1995). Status of sea turtles in the central Pacific Ocean. In K.A. Bjorndal (Ed.), Biology and conservation of sea turtles (pp. 243-252). Washington, DC: Smithsonian Institution Press.

Balazs, G.H., Rice, M., Murakawa, S.K.K., & Watson, G. (1996, June). Growth rates and residency of immature green turtles at Kiholo Bay, Hawaii. Proceedings of the Sixteenth Annual Symposium on Sea Turtle Biology and Conservation, Hilton Head, SC.

Whittow, G.C., & Balazs, G.H. (1982). Basking behavior of the Hawaiian green turtle. Pacific Science, 36(2), 129-139