Earth Institute News

posted 06/27/05

Sea Turtles’ Long, Dangerous Trip Home

By Joe Spring, Columbia University Earth and Environmental Sciences Journalism Student

Surrounded by sharks, seals, and thousands of seabirds, the turtles are about the only thing here that reminds me of home. When I was six, my brother and I used to sneak across the railroad tracks that line the Mississippi River on hot summer afternoons and search the muddy water for painted turtles. Now, I crawl behind 300-pound sea turtles as they climb onto the beach at night to lay their eggs.

From sunset to past sunrise, I make seven two-hour laps of the island looking for nesting turtles. My primary survey site is East Island, an eleven-acre spit of sand that is part of French Frigate Shoals and one of the main nesting sites for green sea turtles in the Pacific.

Every time I find one, I record the length of her shell, whether she has any previous tags, her nesting behaviors, and any physical abnormalities I see. The two main abnormalities I find are tumors and missing flippers. Missing flippers are usually the result of attacks by tiger sharks, the only known predators (besides humans) of adult green sea turtles.

Tumors are the other abnormality I most often seen on nesting turtles here—and the one I'm most interested in. More than half of the turtles in the hardest-hit areas have tumors. The tumors have also been found worldwide in all seven species of sea turtle, but green sea turtles in Hawaii, Australia, Florida, the Caribbean and Indonesia have been particularly afflicted.

The tumors vary in size and color, ranging from a pink and bulbous mass the size of my fist, to green and yellow, like the turtle's skin, and smaller than the tip of my pinkie. As part of my research, I take small samples of the tumors so that Terry Spraker, a veterinary pathologist at Colorado State University, can determine if the tumors are advancing or regressing. Understanding the tumors should help give a better understanding of fibropapillomatosis, the mysterious disease that causes them.

Some scientists believe the tumors start on the eyes and spread to other parts of the body. Although they are most often found on the flippers and eyes, they can appear on the shell, in the mouth and lungs, on internal organs, and on the tail. As the tumors grow they can inhibit a turtle's breathing, prevent feeding and digestion, hinder swimming, and cause blindness. Often, the tumors are fatal.

Despite the work of scientists like my adviser, Dr. Alonso Aguirre, the head of conservation medicine at the Wildlife Trust and a world expert on fibropapillomatosis, no one knows exactly what is causing the disease. It was first discovered in 1938 in a New York aquarium and later that same year in turtles captured in the Florida Keys. About 20 years ago, certain bays and lagoons in Florida and Hawaii showed sharp increases in the number of turtles afflicted with the tumors.

Scientists believe an infection similar to a herpes virus combines with other factors to cause the tumors. Suspects include biotoxins and ultraviolet radiation, but the exact cause has proved elusive. One clue may lie in the fact that many areas showing a high prevalence of tumors tend to be stagnant, shallow water environments that receive runoff from agricultural or urban areas.

All seven species of sea turtle are listed as either threatened or endangered, and understanding the cause of fibropapillomatosis might one day lead to help for a group of animals that are certainly in need of some. In addition, the tumors I'm sampling on East Island might one day help us better understand coastal environments around the world. If it turns out that something in the environment is causing the tumors, then it may be that, the turtles I follow are also trying to tell us something is seriously wrong with the waters that we swim and fish.

Related Links:

Wildlife Trust
Info on Sea Turtles
The Columbia University Earth and Environmental Sciences Journalism Program
The U.S. Fish and Wildlife Service -- Green Sea Turtles
The National Marine Fisheries Service -- Green Sea Turtles