Sea Turtles / Marine Life

DIVING WITH SOUTH FLORIDA’S ANCIENT MARINERS

BY WALT STEARNS

The nickname Ancient Mariner is a fitting name for sea turtles, as the ones we see today are surviving relics from our ocean’s prehistoric past.

Remarkably adapted to an almost complete aquatic existence, these marine reptiles actually emerged from a marsh-dwelling ancestor some 150 million years ago. To survive as they have in an open ocean full of apex predators, their bodies had to evolve in ways that allowed them to evade pursuers. Physical changes included a substantial increase in the shape and size of fore flippers to give them greater speed, an increase in body mass to make them less desirable as prey, and increased diving capabilities over their fresh water kin, both for evasion from predators and to enhance their ability to find food. And, like all mariners who are born on land go to sea, the must return now and again to the place of their birth for the next generation to begin.

Encounters with sea turtles are a highlight to any dive. Seeing one move underwater, using their elongated, paddle-like fore flippers with strong graceful and powerful strokes is somewhat like watching a bird in flight.

There's a chance of seeing at least one of the world's seven species of sea turtles at almost any tropical region, but some places are better than others. Having spent more than 25 years traveling to various corners of the tropical Atlantis, Caribbean, and Pacific, I can comfortably assert that very few dive destinations in the world can compare to the waters off Florida’s Palm Beaches for finding these ancient mariners.

The topography along this part of the Florida coast is ideal for turtles, both above and below the water. The Gulf Stream, with its river of warm, tropical water, sweeps close to shore, bringing warmer water in up the surf line during even the coldest times of the year, this ensures a comfortable environment for both resident and transient species of these marine reptiles. In addition, many area reefs are deeply undercut, providing shelter from surge and predators while the turtles sleep.

Divers in the Palm Beach area are accustomed to seeing turtles on a regular basis. On any given dive, it’s quite common to run into two or three hawksbills cruising through a patch of soft coral, or to find a large loggerhead or two roaming the reefs or snoozing beneath a ledge. Anything less would be considered a slow day, and I’ve had the good fortune of seeing not only hawksbill and loggerheads but also a green or two all on the same dive. And if you’re really lucking, encounters can include a Kemp’s Ridley or the giant of the turtle clan, the Atlantic leatherback.

While any time of year is good for seeing turtles off the Palm Beach coast, the best opportunities occur in the months following the first day of spring. This is because the Palm Beach area is a major breeding and nesting ground for three of the Atlantic Ocean’s five species: green, loggerhead and leatherback. And when nesting season reaches its peak, between the months of May and July, this coastline plays host to more sea turtles per acre than anywhere in the Southeastern U.S. or Caribbean.

 

Leatherback Sea Turtle

Turtle nesting season in Florida begins in early March with the leatherback (Dermochelys coriacea). At full maturity, a leatherback will measure 4-6 feet (1.2 to 1.9 meters) in length, and weigh from 440 to 1,100 pounds (200 to 500 kgs.). The largest leatherback recorded was 6.5 feet (1.98 meters) in length, and tipped the scales at 2,019 pounds (915 kgs.), making it a colossus in the world of living sea turtles. In the water or on the beach, there is no mistaking this creature, which has   predominantly black body with white markings and a teardrop-shaped leathery carapace instead of a hard shell.

Leatherbacks are intriguing; as they are holdovers from an era some 75 to 100 million years ago when sea turtles had obtained the size of giants. The largest of these was a species called Archelon, which grew to 13.5 feet (4 meters) in length, with a flipper span of 16 feet (4.9 meters). Like their ancestral forerunner, leatherback sea turtles differ from the rest of present day sea turtles in that they do not have a solid shell, but instead have a skeletal framework covered by a leathery carapace. They feature remarkable adaptations for life in the open sea, including a large amount of oil in their bodies, which gives them their unique ability to maintain their core body temperatures in waters cold enough to kill other species of sea turtles. This is an important feature, as many of the jellyfish they feed on are found more readily in the northern and southern latitudes of the Atlantic, Pacific and Indian Ocean. In the Atlantic, leatherbacks regularly inhabit regions as for north as Maine to as far as South as South Africa’s Cape of Good Hope.

But because they are still retiles, they require more tropical and subtropical climes when it comes time to nest and lay eggs. The most significant Atlantic nesting sites are in Suriname, French Guiana and Trinidad & Tobago in the Caribbean, and Gabon in Central Africa. But while these regions remain their primary nesting sites, several hundred leatherbacks nest annually on the eastern coast of Florida, with the epicenter of this activity being the northern half of Palm Beach County.

Since 2001, Juno Beach’s Loggerhead Marinelife Center has documented 360 individuals that have come ashore to nest between the Jupiter Inlet and the Lake Worth Inlet. While in the area, a female may come ashore as many as eight or nine times, over a 12-week period, laying a clutch of up to 100 eggs with each landing. Their egg laying ends between mid May and early June. Using satellite tags, the Loggerhead Marinelife Center has been able follow 25 of these turtles as they make their way as for north as Newfoundland and eastward to the coast of Africa.

 

Loggerhead Sea Turtle

Next up in the nesting season is the Loggerhead (Caretta caretta), an impressive creature easily recognized by its thick, rough-textured shell and large blunt, head, which looks like the end of a log, Hence the name. Loggerheads are found in both the Atlantic and Pacific, although they seem to grow to greater sizes in the Atlantic. Mature turtles average around 4 feet (1.2 meters) in length, but it’s not unusual to come across adult females measuring 5 feet (1.5 meters) and weighing up to 500 pounds (226 kgs.). In addition to being the third largest of the marine turtles, they are also omnivorous, dining on just about anything they can get—jellyfish, crustaceans, and even dead fish. This dietary habit has made them highly susceptible to baited long lines set by commercial fishermen.

When it comes to sighting loggerheads, Florida ranks number one, with the northern Bahamas coming in a close second. This is not surprising, as the Florida coast is one of the Loggerhead’s leading reproductive grounds. From May through August, resident turtles are joined by transient individuals, causing the population in the area to swell considerably in number.

During mating season, the yearly ritual among adult male loggerheads can get very heated, as they jockeying for the chance to mate with viable females. This can sometimes escalate into a fight between potential suitors.

By the height of nesting season, June, its not unheard of to count as many as 20 to 30 adult loggerheads scattered up and down reefs systems like Breakers Reef straight off shore Palm Beach Island. Often times the either fast asleep of in a stupor from being ashore the previous night.

To haul such a large body, not designed to function on land, up a sandy slope, dig a hole deep enough to bury the 100 eggs they will lay, only drag themselves back the sea takes a great deal of physical effort. The most telling evidence of this taxing exercise was when you see some of the turtles seemly so bugged out that they will barely make to the reef before falling asleep in their tracks. Even more comical are the ones settling in for a long nap under a small overhand barely large enough to conceal their head, while leaving their massive body exposed looking all to the world  like a poor attempt in parking a large truck in small tool shed.

 

Green Sea Turtle

The latecomers in the nesting season are green sea turtles (Chelonia mydas). The second largest in the sea turtle family, an adult female can grow to 5 feet (1.5 meters) in length, with some individuals weighting as much as 690 pounds (315 kgs.). Most adult greens seen on the reefs near Palm Beach average between 240 and 420 pounds (110–190 kgs.), which is still pretty big. Although similar in size to Loggerheads, greens are really easy to identify by their smooth, olive-brown carapace (shell) marked with darker streaks and/or spots, and equally smooth bullet shaped head. The name green sea turtle was actually derived from the greenish color of its body fat, not its skin or shell.

Green sea turtles have life spans of up to 70-80 years. They are primarily nomadic, migrating from feeding grounds to the nesting grounds of their birth and back again. While most follow coastlines, some will move across the open Atlantic. For example, one population swims from Brazil to nesting grounds on Ascension Island, which is about 1,000 miles (1,600 kilometers) off the coast of Africa.

Greens are not as abundant off the Florida coast as Loggerheads and hawksbills, and most seen by divers are juveniles less than two feet in length. Still, a good number of the big moms come to the Palm Beaches between early June and the end of September to lay their eggs. And as with the loggerheads, it’s a good bet you’ll find them on the same reefs, resting up from their previous night’s journey onto the beach.

 

Hawksbill Sea Turtle

It’s rare not to see hawksbill sea turtles when diving the reefs offshore of the Palm Beaches. Next to loggerheads, the Atlantic hawksbill (Eretmochelys imbricata) is the second most abundant species of sea turtle off this coast. Smaller and more agile that the other species, hawksbill’s are easily identified by the ornate coloration of they’re shell and their protruding upper jaw, which resembles a hawk’s beak. It was the unique color pattern in their shells that once made them highly sought after for tortoise-shell jewelry and ornaments. Nowadays, their biggest dangers are development of nesting beaches and poaching of their eggs, despite their global protected status.

An interesting fact about hawkbills is that they do not nest on beaches along Florida's southeast coast. Instead, their primary nesting grounds take place in the Caribbean. In addition, nesting is not seasonal, but instead takes place year round. Most of the hawksbill turtles we see off the Palm Beach coast are juveniles that are two to three feet in length, and not yet sexually mature. A fully mature adult will measure 45 inches (1.1 meters) in length, and weigh around 190 pounds (86 kgs.). If you run into a larger hawksbill, it’s likely a transient that’s just passing through.

 

Kemp's Ridley Sea Turtle

So we have four out of five: leatherback, loggerhead, green and hawksbill. The fifth species, the Kemp's Ridley (Lepidochelys kempii), shares most of the physical attributes as their Eastern Pacific kin, the Olive Ridley (Lepidochelys olivacea). The Kemp has a round, semi-flattened carapace. They are the smallest species of sea turtle, reaching maturity at two to three feet (60 to 90 cm.) in length, averaging no more than 100 pounds (45 kgs.). They might be mistaken for a young loggerhead, except their shell is smooth, not rough, and the coloration is more grey and light tan than dark brown.

At one time, Ridleys were the most prolific species of sea turtles in the Gulf of Mexico, ranging from the coast of Alabama southward to the Campeche Bank, near the Yucatan Peninsula. Colonial records from the early 1700-1800’s describe the beaches on both sides of the Gulf as being covered by nesting turtles. Hunting and coastal development took a toll on the turtle population. It 1947, it was estimated that the entire nesting population of Ridley’s in the Gulf numbered around 92,000. The first large scale surveys conducted between 1978 and 1988 revealed alarming decline, with the number of nests having fallen to around 800, and a continuing downward trend of 14 fewer nests each successive year. Today, the total number of nesting females may be as low as 350 through out their entire range.

Although found predominantly in the Gulf of Mexico, an extremely small population of Kemp’s Ridleys lives off Florida’s eastern coast between Jacksonville and the northernmost end of the Palm Beaches in Jupiter.

 

Photo Etiquette for Sea Turtles

Sea turtles are a favorite subject for underwater photography. But though they are large, they are also shy and easily intimidated. Shooters who pursue a turtle with too much enthusiasm may not only loose the shot by scaring the turtle away, but also cause the animal undue stress. The best photo opportunities come to those who are patient. The key to approaching sea turtles is to make your movements slow and deliberate. Oftentimes, when they don't feel threatened, turtles may be inquisitive and will come close for a better look. Above all, don’t swim directly at them. That will make them feel threatened and will cause them to bolt in an instant. When that happens, you will soon discover that when sea turtles really want to get somewhere, they are anything but slow.

 

Relevant Links:

The Comprehensive Florida hawksbill Research and Conservation Program - www.floridahawksbills.com

Caribbean Conservation Corporation – http://www.cccturtle.org/satelliteturtles.php

NOAA Fisheries listing of Marine Turtle Species Under NMFS Jurisdiction - www.nmfs.noaa.gov/pr/species/esa/turtles.htm

Cretaceous Period - http://en.wikipedia.org/wiki/Late_Cretaceous

Clutches – http://en.wikipedia.org/wiki/Clutch_(eggs)

Loggerhead Marinelife Center - http://www.marinelife.org/