For the giant Aldabra tortoise, love, like most other aspects of life, is slow-moving but steady. Very steady. The four Aldabras at the National Zoo don’t have much variety in their routine. They spend much of their time lying around. They munch on hay, lots of it. And they copulate.

The Aldabra tortoises, the second-largest tortoises in the world, come from Aldabra Atoll in the Indian Ocean. Those at the National Zoo live in a spare concrete pen near the front entrance of the reptile house, around the corner from the crocodiles and just feet away from the Burmese python. In the summer, they move to an outdoor exhibit.

The zoo has two males and two females—massive, sluggish, with high-domed, dark-green shells. The males are larger; the bigger one weighs in at about 575 pounds, roughly one-and-one-half times the size of the smaller of the females. None of them have names, according to zoo officials.

The big male is the most amorous of the bunch, particularly in the morning. Or after a quick wash-down or a dip in the pool. Or after grabbing a bite to eat. Or whenever it is slightly humid; moisture, zoo officials say, definitely brings on his urges.

Besides being the largest, he is thought to be the oldest of the tortoises on display. He and one of the females were well into adulthood when the National Zoo acquired them in 1956. The second pair, another adult male and female, arrived 20 years later.

Curators speculate that the big male might be nearing 80. No one knows his age for sure. What zoo workers do know is that he has been having sex almost daily—sometimes more often, sometimes less—for the last 47 years. Scientists estimate that giant tortoises can live more than 150 years—all while maintaining a sex drive that Hugh Hefner would envy.

During intercourse, the big male emits a deep, primal moan that sounds like something between a lion’s roar and the diesel rumble of the giant yachts that sail up and down the Potomac River. Sometimes the moan is as loud as the whistle of a freight train, and the act itself can last for hours.

“It’s no secret that our tortoises have a remarkably healthy sex life,” says Monika Holland, an animal keeper at the zoo’s reptile house. “We all laugh about it, because when they are doing it, you can’t ignore it. It’s incredibly noisy. It even scares the little kids.”

To date, no little turtles have emerged as a result of the daily romps. Breeding Aldabra tortoises in captivity is notoriously difficult. Only three zoos in the United States have successfully accomplished the feat. At the National Zoo, animal keepers have questioned whether the big male and the others are simply going through the motions, rather than actually copulating. One reason they’re unsure: The tortoises’ shells obscure the view of what’s really going on.

“What we do know is that they are always making attempts to mate,” Holland says. “In fact, sometimes it seems like they are making those attempts all the time—but so far, we’re unable to tell if they have actually copulated or not.”

On a Sunday morning, a zoo worker cleaning out the Aldabras’ exhibit has lightly misted one of the females, transforming her previously dusty shell to a shiny green. As she moves to munch on a stash of hay and vegetables, the big male slowly approaches from behind. While the two other tortoises watch, the big male attempts to mount the female by climbing on top of her, but she rebuffs him, instantly collapsing to the ground and retreating into her shell.

The big male loses his balance and tips partway onto his side, then slowly regroups and heads to the exhibit’s pool. There he drinks water for several minutes.

A short time later, he tries to mate with the same female again, to the alarm of a group of small children who have just arrived with their parents. As flashbulbs erupt, emotional chaos ensues.

“Oh my god, Daddy! What is he doing to that turtle?” one little boy exclaims.

As the crowd grows, the big male mounts the back of his partner, his forelegs near the front of her shell, and slowly launches into a thrusting motion. The friction of their shells creates a faint scraping sound, muffled by the glass of the exhibit area.

A group of teenagers in town from Madison, Wis., giggle as the big male, opening his mouth to reveal a bright pink tongue, emits a bellow that seems to vibrate throughout the building.

“Cool!” one boy yells.

Susan Tolbert, visiting from Dallas, tries to comfort her horrified 5-year-old daughter, Mason. “It’s OK,” she says. “The turtle’s mommy is right there.”

The mating dance soon ends: The big male sounds a few more deep groans, and then the skittish female puts a stop to it. She strides away, the big male sliding down her back and onto the ground. He retreats into his shell and stays there for several minutes.

Afterward, Tolbert nervously laughs about the incident. “I’m glad that he had, um, performance issues,” she says. “I’m not ready to explain the birds and bees to my kids just yet.” CP

More from WCP