B Read and check your guesses in Ex. 3A.

• Add to the chart you did in Ex. 3A or correct if necessary.

Life History Although sea turtles move swiftly in the ocean, they are slow and defenseless on land. Female sea turtles leave the ocean only to lay egg and, for most species, nest only at night. After about two months, the hatchling turtles emerge at night. The light reflected off the water from the sky guides them to the sea. These days, car headlights, street lamps, or lights on buildings near the beach cause some hatchlings to travel in the wrong direction. Waiting herons make fast meals of other hatchlings. Any babies still on the beach in the morning are easily picked off by predators or die in the hot sun. It is thought that when the surviving hatchlings reach maturity, they return to the beach where they hatched to lay their eggs.

3C Read these communications from a site about one of the marine turtle species –
ridley sea turtle – and add more information in the chart in Ex. 3A.

Natural Threats Hatchling sea turtles have many enemies: ants, crabs, lizards, birds, dogs, raccoons, pigs, coyotes, and many carnivorous fish and dolphins. Man's impact on all life history stages has been considerable. Mature marine turtles, which are both fast and heavily armoured, have few natural enemies. Sharks and man pose the only real threat.  

Population Trends The principal cause of the historical, worldwide decline of the olive ridley sea turtle is long-term collection of eggs and killing of females on nesting beaches. Because arribadas concentrate females and nests in time and space, they allow for mass killing of adult females as well as the taking of an extraordinary number of eggs. These threats continue in some areas of the world today, compromising efforts to recover this species. Additionally, incidental captures in fishing gear is a serious ongoing source of mortality that adversely affects the species' recovery. Specifically, incidental capture of sea turtles in shrimp trawls along the coast of Central America is estimated as exceeding 60,000 sea turtles annually, most of which are olive ridleys.

Declines in olive ridley populations have been observed attributed to coastal development resulting in a loss of nesting habitat. This species is also threatened by human impact. Pesticides, heavy metals and PCBs have been detected in turtles and eggs, but their effect is unknown. Oil spills cause respiratory, skin, blood and salt gland problems. Marine debris such as plastic bags, plastic and styrofoam, tar, balloons and plastic pellets have been discovered in dead olive ridley stomachs. Consumption of synthetic materials interferes with metabolism and harms the animal through absorbtion of toxic byproducts. Marine recreation, boating, and ship traffic also threatens this species due to propeller and collision injuries.

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