Originally created 01/08/01

Turtles provide clues on aging

In his approach to studying turtles, Justin Congdon has taken the moral of the tortoise and hare story to heart: It is what happens in the long haul that counts. His patient and meticulous study during the past 26 years also seems to support the theory of evolution.

Dr. Congdon, a senior research ecologist at Savannah River Ecology Laboratory, recently was awarded the 2000 Longevity Prize by Fondation IPSEN, a French organization that supports research into longevity and aging. Since 1975, Dr. Congdon has been tracking and cataloging the life histories of thousands of turtles at places such as the E.S. George Reserve at the University of Michigan and El Coronado Ranch in Arizona. His work at E.S. George incorporates turtle-tracking studies that began in 1953, including some of turtles that still survive and are part of current studies, giving Dr. Congdon an incredible database to analyze.

"It's pretty unique in that that type of long-term data-set doesn't exist anywhere else," Dr. Congdon said.

Though he has studied snapping turtles and painted turtles, his most recent paper focuses on Blanding's turtles, which he has tracked since he was a student at Michigan and was recruited by his mentor, Don Tinkle.

The latest paper, which will be published sometime this year in the Journal of Experimental Gerontology, compares a set of female Blanding's turtles 35 to 50 years old to a set of females 50 to 65 years old. The most common theory of aging, called senescence theory, is that performance and survival decline with age, Dr. Congdon said. But in fact, Dr. Congdon found the opposite is true in Blanding's turtles: Not only do both older male and female turtles survive better, but the older females also reproduce more and lay more eggs, which are is supportive of an evolution of longevity, Dr. Congdon said.

"So you get this turtle over her lifetime, reproducing more at an older age and (contributing) more offspring at an older age than she does at a younger age (and) produces more offspring carrying those traits," Dr. Congdon said. "It supports evolutionary theory way, way more than it supports senescence theory."

Blanding's turtles continue reproducing and passing on their genes until they die, unlike humans.

Most of the studies on aging and life histories have been done on animals with much shorter life spans, such as monkeys or fruit flies, for obvious reasons, Dr. Congdon said.

"But does that model pick up and translate to a long-lived animal? I surely don't think so," Dr. Congdon said. "Even though it's difficult and there are some things that are impossible, we've got to study long-lived animals if we're going to understand the other specifics of aging."

People may be clinging to concepts about aging that should be re-examined, said Whit Gibbons, the senior ecologist at Savannah River Ecology Laboratory and a famous turtle and reptile researcher himself.

"You do get these mind-sets and paradigms that people don't think beyond them," Dr. Gibbons said.

Dr. Congdon's work might be part of changing that, he said.

"I think that Justin's studies are just remarkable," he said. "There is much to be learned out in the natural world. We need this kind of work to bring it out."

The depth and breadth of Dr. Congdon's cataloging can be seen as he picks up a turtle shell and sets it on his desk. He notes the notches in the edge of the shell on each side, which is part of the turtle's code - nine right, 12 left. Then he types the code into the database, and the turtle's records instantly pop up.

"That animal was first marked in 1976," he said, staring at the screen. Each successive year, the animal was recaptured, Dr. Congdon said, until June 21, 1988, when the turtle was found dead, killed by a raccoon. And then he remembers the story - one of the students helping him had reported the turtle wasn't nesting.

"She's not nesting because the flies are bothering her," the student told Dr. Congdon. Intrigued, he followed the student back to the area and raised his binoculars; it was obvious to him what had happened.

"Well, the flies are there," Dr. Congdon said, "but I don't think they're bothering her."

His work is made possible by the reserve, 1,500 pristine acres near Pinckney, Mich., that is protected by a 12-foot fence. But it happens only because of his dedication and the dedication of his volunteers, he said. During the nesting season of May through early July, he and the volunteers spend from 6 a.m. to sometimes 1 or 2 a.m. each day tracking, recapturing and marking the turtles, X-raying the pregnant females to count their eggs, protecting the nests from predators with small fences, and cataloging the hatchlings, which become part of the study.

"People ask me why I do this year after year, and I can tell you it's still fun," said Dr. Congdon, who turned 60 last week. "It is work, believe me. My life would be much simpler without the Michigan study. But my life wouldn't be nearly as interesting without the Michigan study."

Put another way, it is the moral of the turtle.

"Persistence is a virtue," Dr. Congdon said.

Reach Tom Corwin at (706) 823-3213.


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