Health & Medicine / Aging

And mice are among a group of short-lived animals, which includes worms, lizards, and fruit flies, that scientists have traditionally used to study aging. With short-lived animals, "you can walk away from a project within three or four years, and you've got a lot of data, and you can make a big impression on your colleagues," says Ronald Nussbaum, a zoologist at the University of Michigan. Under such pressures, turtles are hardly the research subject of choice.

Why don't turtles operate like mice? One reason is their shell, which makes them less vulnerable to predators. At the same time, because they spend much of their early years developing their shells, they delay sexual maturity. Because turtles begin reproducing so late, and the vast majority of their young don't survive, evolution favored those individuals that were able to keep pumping out eggs.

With the Blanding's Turtles in particular, not only are the old females still fertile, they're often more productive and have a higher survival rate than their daughters and granddaughters. Congdon's theory: Age brings wisdom, even in reptiles. "Blanding's Turtles know a lot about the landscape that they live in," Congdon says. "I'm not just talking about the immediate landscape. We have animals that travel four kilometers [2 1/2 miles] to nest. Do they know where they are when they are four kilometers away from where they started out? Yes. Did they have some innate, built-in map? No, they learned that route over years and years. So if a female goes to a place and it is not a successful nesting site, the old ones know where to find the next-best place better than the young ones. When you make it to your sixties with no doctors, you are the best of the best. Certainly, you can get run over by a mower. But maybe older females have a slight edge in avoiding risk."

He knows this is hard for many people to believe. "When you dissect a turtle's brain, you just go, 'Boy, there is not a lot of room in there for a lot of thought.' I mean, they are tiny, tiny brains. But I think these turtles are way smarter than we give them credit for." When Congdon retires and has enough time, he'd like to "train turtles to see how much they can learn. I think they could learn a lot."

While Congdon is developing life-history data on individual captures, other researchers are trying to get a better grasp on why the animals resist senescence. "The turtles are vertebrates, so they're reasonably closely related to us," says Steven Austad, professor of biology at the University of Idaho. "To the extent that, on a cellular level, these turtles show resistance to the stresses that damage human cells, they might have something to teach us."

James Christiansen, professor of biology at Drake University in Des Moines, is studying how telomeres, the simple, non-genetic DNA sequences that sheathe the ends of chromosomes, function in reptiles. Each time a healthy human cell divides, it loses a little bit of the telomere, until the strands are too short to protect the chromosomes. At that point the DNA in a cell begins to break down, which triggers senescence and death. Human cancer cells go off the program, producing an enzyme called telomerase that stops the shortening and renders the malignant cells immortal.

Turtles seem to follow a different pattern. "Even though many species live in some of our most polluted environments," Christiansen says, "they avoid cancer." Early results of his study suggest that some reptiles may receive a short burst of telomerase early in life, which makes healthy cells rather than cancerous ones immortal. If this proves to be the case, he says, the human implications may be dazzling. "If we could do that with humans shortly after birth, before the mutations have a chance to creep in," he says, "we could potentially add a hundred years to the human life span."

At 61, Congdon is increasingly aware of his own age. "I feel it," he says. "I don't think a lot about it. I feel it in terms of not being able to go and go and go without paying. I smile when the old Blanding's ladies look at me, and I imagine them saying, 'OK, go ahead, bother me today, but I'm going to outlive you.'" Congdon also fears the turtles will outlive the Michigan study. He plans to return to the reserve for five more summers— but will there be anyone to take over after he retires? "I have been told how valuable the research is," he says. "I've been told how a number of people want my data. I have yet to be told, 'I want the work.' So I don't have anybody on the horizon."

Today, though, he has more pressing concerns, like the fact that the late-spring chill seems to be stopping the turtles from building nests. About a half hour ago, he airlifted a 19-year-old female, tagged with a large number 5, over the East Marsh fence to build her nest, but he's concerned about the cloud cover and approaching cold. "She'll either commit really quick, or she won't," he says. "When the temperature goes down, all the biological processes— strength, muscle coordination, ability to export oxygen to the legs— go down." No. 5 makes her way up the side of an old gravel pit, finds her spot, and starts digging, but then hits a root and abandons the unfinished nest. She slowly inches farther up the hill, but the air has cooled noticeably. She gives up.

Back at the turtle shed, Congdon hears better news. Jason Sweas, his undergraduate assistant from the University of Michigan, has witnessed the first successful nesting of the season, on a lawn near the entrance gate. For an hour he watched as a Midlands Painted Turtle lowered her back end into the hole, laid her eggs, then spent an eternity covering them. She stretched one hind leg as far as it would go, then the other, with each stroke pulling some more soil back over the nest until her efforts were almost invisible. When she was finished, Sweas captured her and carried her to the shed.

He also brought a young male he had spied lumbering around with his shell cracked after he was hit by a car. "The spine's not broken," Congdon notes, so he cuts a four-inch strip of black electrical tape, applies it to the broken carapace, then spreads an adhesive over the tape. "The epoxy will hold it together until the bone grows back. Then it will fall off," he explains. "My guess is that we'll see this guy, with a slightly damaged carapace, years from now. I guess, technically, we shouldn't do this stuff. But I don't think we've changed the demography in any measurable way. If I could measure that accurately, I'd be a very happy guy."

It's time to think about knocking off work and having a beer. The successful nester and the injured male will live in Congdon's utility-room sink overnight and be returned to their swamp home in the morning. Before settling in for the evening, though, Congdon walks East Marsh one last time. He releases No. 5, and she swims back into the marsh, presumably to lay her eggs another day. Congdon watches her as she paddles through the water. Despite his insistence that he has no emotional attachment to his subjects, there's a look in his eyes that conveys the gruff affection he has developed for the critters.

Verbally, though, he concedes nothing. "Another day," he says simply. "Another turtle."

A good starting spot for turtle information.