Sea Turtle Life History Posters
click a turtle to download species-specific life-history posters
A sea turtle encounters natural predators from the time it is laid as an egg all the way through adulthood. Animals such as raccoon, ghost crabs, and dogs dig their way to a sea turtle nest buried about two feet under the surface. Here in coastal Georgia, feral hogs and fire ants are also a problem. These predators continue to be a threat as surviving hatchlings exit the nest. Sea gulls become an additional concern. Once hatchlings reach the safety of the water, most of these predators are no longer a threat. Unfortunately, as the hatchling grows to a juvenile, to a sub-adult, and eventually an adult (30+ years), large fish (such as groupers), sharks, and killer whales will consider them prey.
Not all natural threats come in the form of predators. Some species of sea turtle are prone to a disease called Fibropapillomatosis (FP). FP is a virus that can cause turtles to develop tumors both internally and externally. The cause of this virus is still unclear, and it is most notably found in the green sea turtle species.
Harmful Algal Blooms
Some marine forms of algae naturally produce chemicals that are toxic to sea turtles and other marine species. A specific example occurs along the western Florida coast in the Gulf of Mexico. This particular area suffers from Harmful Algal Blooms, or “red tide”. Marine algae are a large part of the green sea turtle’s diet, and ingestion of these toxins can lead to sickness or even death. Other sea turtle species are at risk due to a process known as bioaccumulation. When small organisms (like shrimp) consume these algae, the toxins can accumulate inside their bodies. Some sea turtles prey on these small organisms, and, as a result, become infected with the toxins. According to the National Oceanic and Atmospheric Administration (NOAA), red-tide related sea turtle deaths in theGulf of Mexico have spiked in recent years.
Another natural threat to sea turtles is Cold Stunning, similar to hypothermia in humans. Since turtles are reptiles, they are ectothermic, meaning they rely on external heat sources to determine their body temperature. Cold-stunning can occur during a sudden drop in temperature, causing sea turtles to experience a decrease in heart rate and a decrease in blood flow. This can be followed by lethargy, shock, pneumonia, and, in some cases, death. As a cold front travels quickly through the ocean, large numbers of turtles can be affected.
While some sea turtle threats are naturally occurring, many are a result of human impact. Human threats to sea turtles include shrimp trawling, boat strikes, dredges,pollution, coastal development, and artificial lighting.
Sea turtles are frequent victims to fishing bycatch, particularly during Shrimp Trawling. Fortunately, thanks to a Georgia shrimper named Sinkey Boone, a Turtle Excluder Device (TED) was developed. The TED consists of a grid of metal bars that fits inside the trawl net, prohibiting larger animals such as sea turtles from passing through. An opening at the top or bottom of the net allows for an easy escape. Small animals such as shrimp are still able to pass through the bars.
Every year, Boat Strikes account for a large number of sea turtle mortalities. Turtles are particularly vulnerable to boats and other vessels, since they frequently surface to breathe. Such encounters result in serious injury and death. Fishing Dredges are a concern for turtles resting on the bottom. This method of fishing involves dragging large metal equipment along ocean bottoms, which can crush sea turtles.
Pollution, such as marine debris and oil, is another common threat to sea turtles. Ingestion of marine debris can cause blockages, affecting digestion and breathing. Entanglement in items such as fishing line can prevent animals from surfacing to breathe, and slows them down, making them more vulnerable to predators. All garbage will eventually break down. However, some items such as Styrofoam can take over 1,000 years to decompose. Sea turtles are highly sensitive to chemical pollutants such as oil. Oil washed ashore after a spill can reach sea turtle nests, leading to underdeveloped eggs and hatchlings. Turtles have permeable skin, meaning substances in the water can secrete into their bodies. Ingested oil can negatively impact their lungs, digestive tract, salt glands, and other organs.
Coastal Development and Beach Erosion damages sea turtle nesting sites. A nesting female will build her nests within 5-30 miles of the location where she was born. If conditions are not ideal, she may decide not to lay a nest. This is known as a false crawl. Recently completed or current construction can deter females from coming ashore.
Artificial Lighting along the beach may deter a nesting female. The use of personal flashlights can frighten would-be nest makers, causing them to retreat back to the ocean. Hatchlings are also threatened by artificial lighting. When a sea turtle hatches, it naturally follows the brightest light towards the horizon to find its way to the ocean. Excess street lights or brightly lit hotel structures can confuse the young hatchlings, distracting them from the horizon. This makes them more prone to predators and, potentially, road traffic.
The most direct human threat to sea turtles is Harvesting or Poaching them for food or production of commercial items. Although the United States prohibits the collection and possession of any item originating from a sea turtle, regulations are not as strict in other areas of the world. In many countries it is culturally acceptable to harvest turtles for their scutes or skin for manufacturing. Turtle eggs are often harvested for food and used as an aphrodisiac. These activities, although frowned upon in our society, are part of that culture’s history and traditions.