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Dive Dry with Dr. Bill

#545: Turtle Island

Back in 2000 after I left my position as vice president of the Conservancy, I decided I needed a good, long vacation. I hadn't really taken one during my years there so I took my accrued vacation pay and went on a three month diving and backpacking trip around the Pacific Ocean... Hong Kong, Thailand, Malaysia, Australia, New Zealand, Fiji, the Cook Islands and Tahiti.

There were many memorable dives and experiences during this adventure, but a key one was while diving the Great Barrier Reef on a liveaboard out of Cairns, Australia. My dive buddy and I hovered next to the reef watching a turtle munch on algae about two feet from my mask. I decided then and there I had to get an underwater video camera and become the Cousteau of Catalina when I returned home. The rest is "history" (well, kind of).

Since then I've filmed anything under the sea that would sit still long enough in front of my camera... but I've only filmed a turtle in our waters once, off Long Point several years ago. I've filmed them in Belize, the Bahamas, the Philippines, Florida and other locations but they are a rare subject in Catalina waters... until recently.

Last year I heard of a number of sightings of a turtle in Lover's Cove and previously I'd received reports of turtle tracks on our backside beaches. Then this year divers began seeing one in the dive park and Descanso Beach, and recently SCICo Port Captain Renzo Sampson showed me pictures of one from Lover's Cove.

Now I know a lot of things about our local marine life (and don't know a lot more!) but turtles are not a subject I'm intimately familiar with (for several reasons... tee hee). Back in my youth in Chicago reptiles were a primary focus of my collecting in the woods and alongside the creeks. Here, marine reptiles are a rarity.

Most of the turtles I've filmed elsewhere were hawksbills or loggerheads, but the ones seen in our waters appear to be green turtles. Although they are found throughout the world in tropical and subtropical seas, and have been seen as far north on "our" coast as Alaska and south to Chile, they are rare in California. There is a population centered in San Diego Bay, and some reported in Orange County. Perhaps if our waters warm due to global climate change, they will be seen more frequently here.

The green turtle's teardrop-shaped carapace or upper shell has five central plates or scutes with four scutes located to each side of them. The color may be gray, green, brown or black. The name green comes from the color of its fat and skin rather than that of the shell. Its head is shorter than most other turtles and cannot be withdrawn into the shell. Males have a longer, more slender carapace than females and a longer tail. These are large turtles with individuals reaching five feet in length and up to 700 pounds, with the record one weighing 871 pounds.

Now I don't think I've met a fat vegan human, but there other species that seem to plump up nicely on a diet of greens. I'm thinking of elephants, cows, bison and... yes, this turtle. Unlike most sea turtles, adult greens feed exclusively on algae (preferring soft greens as well as sea grasses) . However the kids are less picky than their parents and will feast on invertebrates including crabs, sponges and jellyfish.

So much for munching; on to the other "M" word. You guessed it! Like other species (including me) these turtles will travel great distances to their mating grounds each year. Once they become sexually mature at 10-50 years (average age 25), males may mate every year while females generally breed every two to four years. I don't blame the girls...it's a lot of hard work for them!

At the breeding grounds, often the same one used by their parents, the poor girls drag themselves up onto the sandy beach and dig a hole in it for the 100-200 eggs they will lay while the boys stay in the water lazily lounging around. It may take the ladies several hours to accomplish this under the cover of darkness to avoid the prying eyes of predators. They then hide the nest by flipping sand over it with their flipper (no relation to the dolphin of the same name). The ladies may even dig a second but empty nest as a decoy. About two months later the eggs hatch and the younguns race toward the sea. Hungry crabs, seabirds and other predators make this one of the most dangerous times of their long (up to at least 80 years) lives. In some countries humans rob the nests early and sell the eggs as a delicacy.

Oh, I usually don't write about another of life's necessities, breathing, in this column but since turtles are air breathers I'll make an exception this week. Most humans can barely hold their breath underwater for a minute and even the best freedivers only go a few minutes longer. When these turtles submerge to sleep on the bottom, they may not resurface for several hours. However, when more active during feeding or while escaping a predator, they may breathe every few minutes. Sure wish I had that ability... I might not need a heavy SCUBA tank to dive!

© 2013 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 29, 10:00 AM weekdays and on Charter Communications Cable channel 33 at 7:30 PM on Tuesdays in the Riverside/Norco area. You can also watch these episodes in iPod format on YouTube through my channel there (drbillbushing). Please help me climb out of self-imposed poverty... buy my DVD's (see this link). Yes, take Dr. Bill home with you... we'll both be glad you did!

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Pictures of green turtle in Lover's Cove courtesy of Renzo Sampson and one at Long Point taken several years ago by Andy Crawford.

This document maintained by Dr. Bill Bushing.
Material and images © 2013 Star Thrower Educational Multimedia