Sea Turtles — Pensacola Beach's Premier Repeat Visitor
There are five species of sea turtles found in the Gulf of Mexico, and three of these are known to nest on Pensacola Beach: the loggerhead, the green, and the Kemp's ridley. The vast majority of these nesting turtles are loggerheads.
Sea turtles navigate back to the beaches where they were born in order to lay their eggs, many times traveling great distances. How they navigate across the oceans is a question marine biologists have tried to answer for years. It is believed that they imprint on the beach before they leave as hatchlings so they can remember the spot when they return. Returning in the spring, the females crawl onto the beach under the cover of darkness, moving above the high tide line and many times all the way to the dune field so that the nest is not overwashed by the waves. The mother turtle digs a nest cavity about three feet deep and deposits about 100 eggs, returning to the water and leaving them to their fate.
After around 45 to 75 days, the eggs will begin to hatch, and the hatchlings will instinctively head towards the water. The newly hatched turtles now face the most dangerous period of their lives. As they move towards the relative safety of the sea, predators such as gulls and crabs attack and feed on them. A significant percentage of the hatchlings never makes it to the ocean, and only 1% will live to sexual maturity.
Land Shots of Sea Turtles, Tracks and Eggs © DJ Zemenick
The sea turtle population faces a number of threats from humans. Turtles are sometimes caught in fishing nets and fishing lines, which prevents them from surfacing for oxygen, eventually drowning them. Beach development can disrupt a female turtle's breeding cycle, preventing her from returning to the beach where she was born to lay her eggs. Plastic bags can be particularly confusing to sea turtles, as turtles may mistake them for jellyfish. There is also a growing concern about the impact of global warming on turtle populations. Since sand temperature at nesting beaches defines the sex of a sea turtle while developing in the egg, there is concern that rising temperatures may produce too many females. However, more research is needed in this area.
Types of Sea Turtles
The loggerhead sea turtle, or simply loggerhead, is the world's largest hard-shelled turtle. The average loggerhead measures around 35 inches long when fully grown, although larger specimens of up to 110 inches have been discovered. The adult loggerhead sea turtle weighs approximately 300 pounds, with the largest specimens weighing in at more than 1,000 pounds.
The loggerhead sea turtle is omnivorous, feeding mainly on bottom-dwelling invertebrates. Its large and powerful jaws serve as an effective tool for dismantling its prey. Young loggerheads are exploited by numerous predators; the eggs are especially vulnerable to terrestrial organisms. Once the turtle reaches adulthood, its formidable size limits predation to large marine animals, such as sharks.
Green Sea Turtles
As one of the first sea turtle species studied, much of what is known of sea turtle ecology comes from the study of green turtles. Their ecology changes drastically with each stage of their life history. Newly emerged hatchlings are carnivorous, bottom-feeding organisms. In contrast, immature juveniles and adults are commonly found in seagrass meadows closer inshore and are herbivorous grazers.
Green sea turtles spend almost all their lives submerged but must breathe air for the oxygen needed to meet the demands of vigorous activity. Green and loggerhead turtles typically dive for about four to five minutes and surface to breathe for one to three seconds. With a single explosive exhalation and rapid inhalation, sea turtles can quickly replace the air in their lungs. The lungs permit a rapid exchange of oxygen and prevent gases from being trapped during deep dives. Sea turtle blood can deliver oxygen efficiently to body tissues even at the pressures encountered during diving.
Green sea turtles can rest or sleep underwater for several hours at a time, but submergence time is much shorter while diving for food or to escape predators. Breath-holding ability is affected by activity and stress, which is why turtles quickly drown in shrimp trawlers and other fishing gear.
Kemp's Ridley Sea Turtle
The Kemp's ridley sea turtle is the most rare living turtle on earth and is currently endangered. It is one of the smaller turtle species, reaching a mature length of 24-35 inches and a weight of 99 pounds. The Kemp's ridley turtle feeds on mollusks, crustaceans, jellyfish, algae or seaweed, and sea urchins. These turtles change color as they mature. As hatchlings, they are almost entirely a dark gray-black, but mature adults have a yellow-green or white plastron (underside) and a gray-green carapace (outer shell.)
These turtles are called Kemp's ridley because Richard Kemp of Key West was the first to send a specimen to researchers at Harvard. However, the etymology of the name "ridley" itself is unknown. At least one source also refers to the Kemp's ridley as a "heartbreak turtle." In her book The Great Ridley Rescue, Pamela Philips writes that the name was coined by fishermen who witnessed the turtles dying after being turned on their backs. The fishermen said the turtles "died of a broken heart.”