Threats to Sea Turtle Survival

Each year thousands of hatchling turtles emerge from their nests along the southeast U.S. coast and enter the Atlantic ocean. Sadly, only an estimated one in 1,000 to 10,000 will survive to adulthood. The natural obstacles faced by young and adult sea turtles are staggering, but it is the increasing threats caused by humans that are driving them to extinction. Today, all sea turtles found in U.S. waters are federally listed as endangered, except for the loggerhead which is listed as threatened.

Natural Threats

In nature, sea turtles face a host of life and death obstacles to their survival. Predators such as raccoons, crabs and ants raid eggs and hatchlings still in the nest. Once they emerge, hatchlings make bite-sized meals for birds, crabs and a host of predators in the ocean. After reaching adulthood, sea turtles are relatively immune to predation, except for the occasional shark attack. These natural threats, however, are not the reasons sea turtle populations have plummeted toward extinction. To understand what really threatens sea turtle survival, we must look at the actions of humans.

Human-Caused Threats

USFWS File Photo

In many cultures around the world, people still harvest sea turtle eggs for consumption. Most countries forbid the taking of eggs, but enforcement is lax, poaching is rampant, and the eggs can often be found for sale in local markets. In these same areas, adult sea turtles are harvested for their meat. Turtle products, such as jewelry made from hawksbill shells, also create a direct threat to sea turtles.

Lack of information about sea turtles leads many Americans to unwittingly support the international trade in these endangered species. Buying and selling turtle products within the U.S. is strictly prohibited by law, but turtle shell jewelry and souvenirs are the most frequent contraband seized by customs officials from tourists returning from the Caribbean. Indirect threats are harder to quantify, but they are likely causing the greatest harm to sea turtle survival.

Commercial Fishing

Photo Courtesy of Marine Fish Network

The waters of the Gulf of Mexico and West Atlantic coast are a major habitat for turtles, but are also the main shrimping grounds in the U.S. Each year, thousands of turtles become entangled in fishing nets and drown. Worldwide, shrimp trawling probably accounts for the incidental death of more juvenile and adult sea turtles than any other source. At one time, as many as 55,000 sea turtles were killed each year in shrimp nets in the southeastern United States alone. In addition, entanglement in drift nets has become an increasing cause of mortality for sea turtles worldwide.

Loggerhead escaping through a TED. NOAA file photo

In the United States, the federal government worked with the commercial shrimp trawl industry to develop Turtle Excluder Devices (TEDs). TEDs are a grid of bars with an opening either at the top or the bottom of the trawl net. The grid is fitted into the neck of a shrimp trawl. Small animals such as shrimp pass through the bars and are caught in the bag end of the trawl. When larger animals, such as marine turtles and sharks are captured in the trawl they strike the grid bars and are ejected through the opening.

Today, all U.S. shrimpers are required to put TEDs in their trawl nets. Unfortunately, not all fishermen comply with the law, and sea turtles continue to drown in shrimp nets.

Marine Debris - Ingestion & Entanglement

USFWS File Photo

Thousands of sea turtles die from eating or becoming entangled in nondegradable debris each year, including packing bands, balloons, pellets, bottles, vinyl films, tar balls, and styrofoam. Trash, particularly plastic bags thrown overboard from boats or dumped near beaches and swept out to sea, is eaten by turtles and becomes a deadly meal. Leatherbacks especially, cannot distinguish between floating jellyfish — a main component of their diet — and floating plastic bags.

Turtles are affected to an unknown, but potentially significant degree, by entanglement in persistent marine debris, including discarded or lost fishing gear including steel and monofilament line, synthetic and natural rope, plastic onion sacks and discarded plastic netting materials. Monofilament line appears to be the principal source of entanglement for sea turtles in US waters.

Artificial Lighting

Florida Fish and Wildlife Conservation Commission File Photo

Nesting turtles once had no trouble finding a quiet, dark beach on which to nest, but now they must compete with tourists, businesses and coastal residents for use of the beach. U.S. beaches are rapidly being lined with seaside condominiums, houses and hotels. Lights from these developments discourage females from nesting and cause hatchlings to become disoriented and wander inland, where they often die of dehydration or predation.

Coastal Armoring

Loggerhead sea turtle tracks along sea wall. Photo Courtesy of Wilma Katz

Coastal armoring includes structures such as sea walls, rock revetments and sandbags that are installed in an attempt to protect beachfront property from erosion. These structures often block female turtles from reaching suitable nesting habitat and accelerate erosion down the beach. Armoring is especially problematic along the east coast of Florida, where beach development is occurring in the very places where sea turtles come to nest by the thousands.

Beach Nourishment & Dredging

Beach nourishment consists of pumping, trucking or otherwise depositing sand on a beach to replace what has been lost to erosion. While beach

US Army Corps of Engineers File Photo

nourishment is often preferable to armoring, it can negatively impact sea turtles if the sand is too compacted for turtles to nest in or if the sand imported is drastically different from native beach sediments, thereby potentially affecting nest-site selection, digging behavior, incubation temperature and the moisture content of nests. If renourishment is allowed to proceed during nesting season, nests can also be buried far beneath the surface or run over by heavy machinery.

Dredging can cause direct threats to sea turtles and their nearshore marine habitats. Hopper dregdes have been directly responsible for the incidential capture and death of hundreds, if not thousands, of sea turtles in the US.

Beach Activities

Human use of nesting beaches can result in negative impacts to nesting turtles, incubating egg clutches and hatchlings. The most serious threat caused by increased human presence on the beach is the disturbance to nesting females. Night-time human activity can prevent sea turtles from emerging on the beach or even cause females to stop nesting and return to the ocean.

Beach Furniture and other recreational equipment (e.g., cabanas, umbrellas, hobie cats, canoes, small boats and beach cycles) can reduce nesting success and increase false crawls on nesting beaches. There is also increasing documentation of nesting females becoming entrapped in beach furniture.

USFWS File Photo

Beach Driving, either at night or during the daytime, can negatively impact sea turtles. Night time driving can disturb nesting females, disorient emerging hatchlings, and crush hatchlings attempting to reach the ocean. Tire ruts left by vehicles can extend the time it takes a hatchling to reach the ocean and increase their chance of being caught by a predator. Driving during the day can cause sand compaction above nests resulting in lower nest success. Additionally, beach driving contributes to erosion, especially during high tides or on narrow beaches.

Pollution

Photo Courtesy of Dean Bagley, UCF

Pollution can have serious impacts on both sea turtles and the food they eat. New research suggests that a disease now killing many sea turtles (fibropapillomas) may be linked to pollution in the oceans and in nearshore waters. When pollution kills aquatic plant and animal life, it also takes away the food sea turtles eat. Oil spills, urban runoff of chemicals, fertilizers and petroleum all contribute to water pollution.

Although these threats to sea turtles and destruction of their habitats seem almost too big to overcome, there are many things within our control that can be changed. Greater public awareness and support for sea turtle conservation is the first priority. By learning more about sea turtles and the threats they face, you can help by alerting decision-makers when various issues need to be addressed.