Poaching of eggs and turtles. Sea turtles and their eggs are poached and sold for their skin, meat, and the use of their shells to adorn various products and goods. Selling sea turtle products is illegal in many countries, including Costa Rica.
Contamination of the oceans by oil spills and chemical substances, such as fertilizers, damages resources on which turtles feed. Also, waste such as plastic bags and bottles that end up in the sea are often confused by turtles for food, which then eat them and die from asphyxiation.
Bycatch and incidental capture of turtles in gill nets and shrimp trawls drown them because they cannot breathe for hours. In many countries, laws exists that require shrimp boats to use a tool called a Turtle Excluder Device (TED), which is set inside the nets and allows turtles to escape if they are caught.
Boats using outboard motors also represent a big threat. Many turtles have been found that have been mutilated by propellers.
Artificial lights and bonfires can confuse hatchlings on their way to the sea. This makes it easier for them to get lost and more vulnerable to predators.
Natural Threats
Sea turtles, like any other living organism, are vulnerable to predators. This vulnerability is dependent on the turtle’s life cycle stage. The species of the predator also changes during the sea turtle’s life cycle stage.
The fact that the females leave their nests unattended after finishing the nesting process makes the incubation period highly vulnerable, especially to changes in weather, predators and to parasites.
Most of the egg and embryonic loss (excluding human action) occurs immediately after nesting. Beaches are usually patrolled by domestic animals (pigs, dogs, cats) and by wild animals (coyotes, raccoons, etc) that sense, through smell, where a nest is and excavate it. The remainder of eggs and embryos in the open nests are finally devoured by birds, crabs, parasites and fungus.
On massive nesting beaches (arribadas), the same turtles that nest represent a threat to other nests. Due to the high nest density, the probability of digging out an old nest while constructing the egg chamber is very high.
Presence of parasites in nests is another factor that threatens the survival of the young. Often, nests are attacked by flies, larvae, mites, ants, and when humidity is high, by fungus and bacteria.
The run towards the Sea
During the few minutes that hatchlings spend running towards the sea, they are exposed to crabs that drag them to their burrows, a wide variety of mammals, and to snakes and birds. Hatchlings are sometimes insolated when they are caught in debris and wastes on the beach, and they might also become disoriented by artificial lights.
Once in the sea, the young face endless number of predators, specifically pelicans, frigate birds, seagulls, cormorants and a great variety of pelagic carnivorous fish such as sharks.
Adults
During the nesting process, female turtles, due to their slow movements, are easy prey for big predators such as crocodiles, jaguars, pumas and coyotes. On beaches close to human settlements, adult females can also be attacked by packs of domestic dogs. In spite of this, the major threat to adult sea turtles is humans.
Alteration and destruction of nesting beaches, egg poaching, meat and shell contraband, contamination of marine ecosystems and incidental capture by commercial fisheries are some of the causes for the decline of many sea turtle populations.
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