Dive Dry with Dr. Bill

#135: At Loggerheads... Not!

I spend most of my time underwater here in the kelp forest diving solo. While I don't advocate solo diving for anyone else unless they feel prepared, I find it usually works best for me. As a videographer, I get immersed in my subject matter and don't always make the perfect buddy. If I dive with someone who isn't sensitive to my work, I may find them wandering into my camera's field of view as I prepare to shoot. And statistically, based on my personal experience, I have a greater chance of a dive incident while diving with a buddy than while diving solo. However, there are times when sharing my dives is far more fun than going it alone. My trip to Florida to dive with buddies Andrea and Stephanie certainly is a good example.

Both of these wonderful women are fun to dive with, not to mention sharing the experiences of our dives during our surface intervals. In addition, their second pair of eyes often means we will find exciting things that I might have overlooked if diving solo since my eye is often glued to my viewfinder. As an accomplished underwater still photographer, Andrea has an especially good eye for finding unique critters and knowing the camera angles I might need to film them from. Today's column focuses on a dive we did at Molasses Reef near Key Largo, Florida.

Turtles are a rare sight here in the kelp forests, but I have had great encounters with several species in the Caribbean , Great Barrier Reef and Asia. In fact, it was while watching a turtle feeding on algae in Australian waters from a few feet away that I decided to finally "dive in" and buy my first underwater video rig. On our recent dive Andrea and I were swimming along the shallow reef when we noticed motion beside a nearby coral head. It was almost as if the coral head itself was moving! As we inched closer, we discovered it was a huge loggerhead turtle... certainly the biggest either of us had seen at 4-5 feet. Gary, our dive boat captain, said it was the biggest one he had ever seen as well.

Marine turtles evolved from land-based ancestors that re-entered the sea during the age of dinosaurs (slightly before I started diving). We moved toward this ancient behemoth slowly so as not to cause it to flee before we could get some good footage. As we approached, it did slowly turn in the opposite direction and eventually started to swim off. I began filming as it turned... only to discover a minute later that my camcorder battery was dying. I can usually film on a single battery for 2-3 days (6-12 dives) in our cold waters, but here in the warmth of the subtropics it was only our fourth dive of the day. Must have been Murphy's Law catching up with me. By shutting the camera off and turning it on again, I was able to get about a dozen short sequences of this incredible reptile as it swam off.

Species of turtles in the Caribbean and elsewhere have not always enjoyed good "relations" with humans. Early explorers and sailors tended to be more interested in them, and their eggs, as a food source while sailing the ocean blue. I'm sure it was a good change of pace from salted fish and rum. In 1978 the US listed the loggerhead as a threatened species, and later it was designated as endangered worldwide. Approximately one third of the global population of this species is found in Florida. In fact they are the most common marine turtle in that state. Loggerhead turtles may also be found in temperate, subtropical and tropical waters throughout the world. In the Atlantic they are known from Newfoundland to Argentina and have been observed from Alaska to Chile in the Pacific Ocean. Most of the records on this coast were juveniles seen off California, so it is possible to see one here in our waters!

An average sized loggerhead may be 2-3 feet and 250 pounds. However, they may reach 3-4 feet in length and 500 pounds, or even bigger as ours attests. They spend much of their time floating at sea or resting on the bottom (until they have to come up for a breath of air). Based on the retrieval of tagged turtles, this species may make long ocean journeys. One individual tagged off Japan was recovered some 7,500 miles away off Baja California!

Loggerheads appear to keep their sex lives to themselves, and little is known about their courtship behavior. Individual adults average 2-3 years between nesting, although some may return in successive years and others wait as long as six years (approaching my record for celibacy). Mating is believed to occur from late March through early June in Florida. The female turtles come ashore at night on open, sandy beaches to lay their eggs. A single female may return to the beach in about two weeks to lay another clutch of eggs. Nesting may continue into September. They dig holes in the sand with their flippers and may lay 100-125 eggs each visit. In 1990 it was estimated that there were as many as 70,000 nests in the southeastern US alone. After nesting in the southeastern United States, the adults disperse throughout their range until ready to reproduce again.

Those eggs which survive hatch in about two months, depending on local temperature. The predominant gender of the young turtles is also dependent on the nest temperature. The young two inch hatchlings move "quickly" (for a turtle) towards the sea to avoid being eaten by birds and other predators. The young are believed to spend their early lives drifting with the algae and debris in areas like the Sargasso Sea until they are about 20" long. At this time they move into shallower coastal waters where they spend most of their adult lives.

Their name comes from their large head. Their strong crushing jaws are used to feed on hard-bodied organisms like molluscs (mussels, clams and oysters) and crustaceans (crabs and shrimp). However the adults may vary their diet by feeding on sponges or jellyfish, the latter while drifting near the surface. They may also feed on a variety of fish which are scavenged rather than captured live. Because they feed on shrimp, shrimp fishing in the area has reduced one available food source for them. Shrimp trawls and gill nets used by some fishermen are a direct cause of mortality as well since these turtles will drown if they are entangled and can't surface for air. The extensive offshore oil and gas exploration in the Gulf of Mexico may also create serious obstacles for these animals. Turtles may also ingest plastic bags or balloons, thinking they are their jellyfish food. Threats on-shore include egg poaching, erosion of sandy beaches, artificial lighting which can confuse the nesting turtles, compaction of sand and direct death by off-road vehicles on beaches. Dredging and coastal development like marinas can also destroy nesting areas.

The slang term "at loggerheads" means to disagree or quarrel. Andrea and I had no dispute about our enjoyment of this dive! Not to mention this is a lady "to dive for" who would make a very appealing "permanent" dive buddy. We are already talking about a future trip to Costa Rica or the Galapagos. Ah, the sacrifices I will make to ensure a good story for my readers!

© 2005 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays.

Loggerhead turtle in process of turning around, large head from which these turtles get their
common name, yellowhead wrasse checking out turtle, and loggerhead swimming away.

This document maintained by Dr. Bill Bushing.
Material and images © 2005 Star Thrower Educational Multimedia