Scientists are still researching sea turtle longevity. Once sea turtles reach sexual maturity, they may have an estimated reproductive life of about 30 years. Given that some species reach maturity at 50 years, an 80-year lifespan is feasible.
Currently there is not an adequate method of aging sea turtles. The most accepted method is to study growth rings of the scales on the carapace and plastron. Scientists count the rings and use a mathematical formula to estimate a turtle's age.
Adult sea turtles have a few predators, mostly large sharks. Tiger sharks, in particular, are known for eating sea turtles. Killer whales have been known to prey on leatherback turtles.
Fishes, dogs, seabirds, raccoons, ghost crabs, and other predators prey on eggs and hatchlings. More than 90% of hatchlings are eaten by predators.
Flatback turtle nests are susceptible to predation by monitor lizards, dingoes, and introduced foxes.
Green sea turtles may develop fibropapillomas (lobed tumor-like growths) on the skin. These growths can reduce vision, obstruct normal swimming and feeding, and increase susceptibility to secondary parasitism and infection.
Hurricanes can severely impact sea turtle nesting success. Almost 90% of sea turtle nesting in the continental U.S. occurs on Florida's beaches. Scientists estimate that more than half of the sea turtle nests on the coast of Florida were washed away by the four hurricanes hitting the coast in 2004.
Sea turtle nesting areas are becoming scarce due to beach development and disturbances. Kemp's ridleys mainly nest on a remote beach in Mexico near the village of Rancho Nuevo (about 161 km, or 100 miles, south of the Texas border). In 1947, scientists witnessed an arribada of more than 42,000 Kemp's ridley turtles in one day. In the 1960s numbers were reduced to less than 5,000 turtles. In 1973, the largest arribada contained only 200 individuals. More recently, a small but growing number of Kemp's ridleys have nested on some beaches along the coast of Texas.
Nesting females and hatchlings are disturbed by the presence of trash on nesting beaches. If trash impedes its crawl up the beach, a female returns to the sea instead of nesting.
The noise and activity of people on the beach also may cause females to return to the sea instead of nesting.
Some sea turtles die when they ingest trash. Leatherbacks are especially susceptible to ingesting plastic, mistaking it for jellyfish.
Thousands of sea turtles drown in commercial shrimp nets each year. Shrimpers accidentally entangle turtles that are foraging where trawlers are working. This mortality may be increasing. In 1947, 5,000 U.S. shrimping trawlers worked in the Gulf of Mexico. That number increased to 15,000 full-time and 40,000 part-time trawlers by 1989.
Artificial lighting on beaches may misrepresent the time of day to turtles attempting to nest. Most turtles are nocturnal nesters, and to a turtle that has not yet come ashore to nest, a brightly lighted beach may signify daylight and inhibit nesting.
Hatchlings can become disoriented by city and street lights when trying to find the surf. Many young turtles actually head away from the ocean and toward parking lots. These animals may be eaten by predators or crushed by cars. Some die from exposure.
Some people illegally collect turtle eggs for food and for their alleged aphrodisiac effect.
Sea turtles are hunted (illegally in this country and, in some cases, legally elsewhere) for their meat and shells, which are used to make combs, eyeglass frames, aphrodisiacs, and curios. The fat of green sea turtles, boiled with cartilage, made a popular soup called calipee, which led to the decline in green sea turtle population numbers.
Deforestation may indirectly threaten sea turtle nests. Costa Rica has one of the highest deforestation rates in the world. Some researchers fear that without the forest to draw up ground water, the water table will rise beneath beaches and drown nests.
Propeller and collision injuries from boats are not uncommon. These types of injuries are more frequent in areas with a high level of recreational boating, such as southern Florida, the Florida Keys, and the United States Virgin Islands.