Peter Tolson holds a baby Cuban boa. The snakes can reach 15 feet. (Katherine Frey/The Washington Post)

It’s an April evening on the island of Cuba, and Peter Tolson is scrambling up a wet ravine in the dark. Tree frogs and rain frogs croak and chirp while Antillean nighthawks chitter overhead. A slice of Caribbean sky is visible between the trees lining the streambed, and an oversize firefly winks against the stars.

With the help of a battered headlamp, Tolson spots a large electric-green lizard snoozing on a branch above the intermittent stream. It’s a Smallwood’s giant anole, which is endemic to this island, meaning it occurs no place else in the world. Tolson finds several smaller anoles also resting on twigs. But these are not the reptiles he is looking for. Tolson is tracking snakes. Recent rains mean there is water in the streambed, and he’s hoping some boas will come down from the hills to drink.

Tan and fit from his hours afield, with close-cropped salt-and-pepper hair, Tolson moves nimbly, with the enthusiasm of a teen, though he is 72 years old. He’s been chasing snakes for five decades in this spot. “This is a very snakey place,” he says, noting that he’s caught “about 10 boas in this little streambed.”

The snakes he seeks are thick and muscular and can reach 15 feet long. They, too, are endemic to Cuba. And they are thriving in a seemingly improbable place: the 45 square miles under United States jurisdiction known as Naval Station Guantanamo Bay. This controversial military base, with its secure perimeter and protective regulations, has become a de facto wildlife refuge, a haven for rare species.

Outside the fence line, noisy debate continues over the U.S. presence on Cuban land and the ethics of using Guantanamo to detain terrorism suspects. Inside the fence line, biologists steadily go about their work, studying the rare wildlife on the base and in its coastal waters. In the untamed corners of Guantanamo, and even among the razor wire and abandoned bunkers, these scientists find wild, unexpected beauty.

Tolson uses a radio receiver to track the 28 adult Cuban boas he is following for a study. (Katherine Frey/The Washington Post)

At night, Tolson wears a battered headlamp rigged to a bulky six-volt lantern battery. (Katherine Frey/The Washington Post)

Tolson, who grew up near Cleveland and developed an early interest in reptiles, was deployed to Guantanamo as a young Marine in 1968. He’d read about Cuban boas, the island’s largest snakes, so when he wasn’t serving as a radio operator, he was out searching for them. “Every spare minute, man, if I had time off, I was up in these hills looking for stuff,” he recalls. “It kept me out of trouble.” It took him six months to find his first boa, hanging on the trusses under the Guantanamo River bridge. “It was a huge thrill,” he says.

A male Cuban emerald hummingbird on base. They are native to Cuba and the Bahamas. (Katherine Frey/The Washington Post)

When Tolson found other unusual reptiles he could not identify, the base librarian directed him to journals of herpetology (the study of amphibians and reptiles), and he began corresponding with the editors. Eventually, he connected with Albert Schwartz, an American herpetologist who had worked extensively in Cuba before the revolution. Schwartz made two trips to Guantanamo to search for reptiles with Tolson and encouraged him to consider a career in the field.

Tolson left the Marines after his tour at Guantanamo and attended Michigan State University on the GI Bill, earning a BS in zoology. Then he received a PhD in biological sciences from the University of Michigan. Meanwhile, he took a job as curator of reptiles at the Toledo Zoo, eventually becoming the zoo’s director of conservation and research. Since August of last year, he has served as director emeritus of conservation and research at the zoo.

Over the years, Tolson has written dozens of papers, and his research has taken him to Jamaica, Haiti, the Dominican Republic, the Turks and Caicos Islands, Puerto Rico and the Virgin Islands. While studying snakes on the Bahamas once, he wore one of his young daughters in a baby carrier. All along, Guantanamo has continued to be the center of his curiosity and, often, his research.

Tolson helps Army Capt. Brittany Marble, a veterinarian at Naval Station Guantanamo Bay, inject lidocaine near the young snake’s tail before inserting an electronic tag. (Katherine Frey/The Washington Post)

Tolson finds no snakes lurking in the dark streambed. So he retrieves his radio gear from a four-wheeler and walks up a dirt road to a knoll. He sweeps the landscape with a handheld antenna and listens for the clicks that will identify one of his snakes. He is currently tracking 28 Cuban boas, each carrying a radio transmitter, in an effort to determine how many individuals are necessary for a sustainable population. He’s been following the snakes for 14 years, visiting twice yearly.

It’s an ambitious study. Tolson — one of a handful of scientists who receive military permission to visit the base independently each year — wants to understand how many snakes survive in each age class. Developing a comprehensive life table will show the trajectory of a population. This has implications not only for the conservation of boas at Guantanamo, but also for their cousins dispersed throughout the Caribbean.

With its healthy population of snakes, good infrastructure and supportive military administrators, Guantanamo is uniquely suited for this research. Indeed, the boas are threatened in the rest of Cuba, where farmers kill them because they sometimes prey on chickens.

Tonight, there are no clicks for Tolson. He estimates it takes him 40 hours of searching to find a new snake and says it can even be difficult to locate those carrying transmitters. The snakes move around, occasionally hanging out in old bunkers, tunnels or pipes, which obstruct the signal.

But driving down from the hills, Tolson spies a young Cuban boa lazing on the pavement in the dark, soaking up the residual warmth. Tolson pulls his four-wheeler to the shoulder and gently scoops up the skinny snake, which is more than two feet long. Curled in his hands, it’s a magnificent creature, quite slender, its back covered with chocolate and tan patterns. He places it in a plastic tote in the bed of his vehicle.

The months-old baby boa tries to escape its container while on the scale. It weighs eight ounces and measures 31 inches. (Katherine Frey/The Washington Post)

The next morning, he takes the snake to a veterinary clinic. Dogs yap from their kennels, and the veterinarian, Army Capt. Brittany Marble, looks busy. But she is pleased to see Tolson and, especially, the snake.

“How old is he?” Marble asks.

“He’s young-of-the-year,” says Tolson, meaning the snake was born this past fall.

“Wow, he’s cute.”

Marble pulls out a plastic box labeled “snake set.” Tolson helps hold the snake as Marble injects a bit of numbing lidocaine near its tail. Then, using an oversize hypodermic needle, she inserts a tiny electronic tag, not much bigger than a short length of pencil lead, that will allow them to identify the snake if it is recaptured. (This is smaller than the radio transmitters implanted in the snakes Tolson is tracking; he already has his hands full with 28.) Tolson identifies the sex of the snake by gently probing its cloaca, an opening near the end of the tail for both the digestive and reproductive organs. It’s a female.

Marble is new to snake work — in vet school she focused on horses, dogs and cats — but it has become a passion. “I’ve learned a lot, and I really, really like snakes,” she says. “It’s my favorite part about being here.”

Once, when Marble and her husband were out jogging, pushing their year-old twins in a stroller, they came across a huge, slightly injured boa in the road. Marble grabbed her husband’s T-shirt and wrapped it over the snake’s head to keep it calm. Then they picked up the snake and set off jogging the two miles to the vet clinic. Marble held the boa’s head as it draped across her shoulders and rested part of its writhing, 35-pound body on the stroller; her husband ran alongside holding the snake’s tail.

The snake had a facial injury, which Marble treated with antibiotics. Then she gave it a transmitter and released it. Now it’s in Tolson’s study.

Tolson and Marble measure the young snake and weigh it on a cat scale — 31 inches, eight ounces — and log the details in a notebook. Then Tolson takes it to a nearby ridge to release it. Up on the hill, the Caribbean sun bakes down. A curlytail lizard basks on a post. A Cuban pygmy owl perches in a nearby shrub, its breathy calls competing with the muted cracks of rifle shots from a distant target range. Down below sprawls the naval base, a small town on the shore of placid, blue Guantanamo Bay.

Tunnels once used to avoid live fire on the firing range are now home to bats, geckos and snakes. (Katherine Frey/The Washington Post)

A Desmarest’s hutia, also called a banana rat. They are less common on other parts of the island. (Katherine Frey/The Washington Post)

With its low buildings strung out along winding roads and cul-de-sacs, its sere hills studded with cactus and palm, its McDonald’s, Pizza Hut and Subway, its well-lit athletic fields and sidewalk-strolling couples, Guantanamo feels like a quiet Southern California suburb. Though it’s on Cuba, you rarely hear a word of Spanish. English laced with military jargon is the first language here, though you might catch some Tagalog or a Caribbean lilt. (The cooking, cleaning and construction on the base are generally done by Filipinos and Jamaicans. Cubans have been barred from being hired here since the revolution; the last two, who were grandfathered in, retired in 2012.) All told, the base is home to about 5,500 people, including sailors, soldiers, Marines, airmen and Coast Guardsmen serving many and varied roles.

Butterflies alight at the beach. (Katherine Frey/The Washington Post)

Guantanamo’s well-protected deepwater harbor has a long history of human settlement — and conflict. When Columbus visited the bay on his second voyage in 1494, he was met by indigenous Tainos; though he named the bay Puerto Grande, its Taino name of Guantanamo stuck. Conquistador Diego Velázquez de Cuéllar followed in 1511 on a quest to subdue Cuba’s inhabitants for the Spanish crown. He sailed to Guantanamo, where he killed and terrorized Tainos while he searched for their rebel leader Hatuey, whom he ultimately caught and burned at the stake. The Spanish went on to decimate most of the Taino population.

The bay also was the site of a key battle of the 1898 Spanish-American War, which was precipitated by Cuban resistance to Spain’s colonial rule. Shortly after the United States entered the war, American troops arrived at Guantanamo and, with support from Cuban soldiers, pushed out the Spaniards. The Americans claimed the eastern mouth of the bay, known as Windward Point, set up camp and never left. In 1903, Cuba leased 45 square miles at the mouth of Guantanamo Bay to the United States, ceding it “complete jurisdiction and control” through a treaty that can only be dissolved by mutual agreement.

For years, Guantanamo was a quiet, noncontentious outpost, home to the Navy’s Fleet Training Group. When Fidel Castro took power in 1959, however, he objected to the Americans’ continued presence at Guantanamo; he once called the base “a dagger plunged into the heart of Cuban soil.” It was the beginning of a standoff that has outlasted the Cold War. The United States has continued sending annual checks for about $4,000, to honor the terms of the lease, but first Fidel, and then his brother Raúl, who took over as president in 2008, refused to cash them. Meanwhile, Guantanamo would house Cuban and Haitian refugees and then, notoriously, suspected terrorists. Barack Obama would promise but fail to close its detention center; Donald Trump would pledge to “load it up with some bad dudes.” Through all of this, the snakes, hidden in the hills, quietly persisted.

The Windward Point Lighthouse in Cuba. (Katherine Frey/The Washington Post)

One hot afternoon, Tolson scrambles along a steep hillside below Cuzco Well, site of a fierce battle where U.S. Marines seized control of the bay’s only fresh water source in 1898. Broken Spanish tile still lies scattered on the ground.

Tolson scans the trees for Desmarest’s hutias (hoo-TEE-uhs), large, nocturnal rodents endemic to Cuba. They can reach 15 pounds and are less common outside of the base, where residents hunt them for food. But inside the fence line they are so abundant that they have become a nuisance. Their curved scat has earned them the moniker “banana rats.”

An adult boa — one longer than nine or 10 feet — will eat a hutia about every three weeks, Tolson says. It will hide in the grass next to the trails hutias frequent and wait until one of the rodents ambles by. Then the boa will nab the hutia with its mouth, squeeze the life out of it and swallow it slowly. (Recent observations from elsewhere in Cuba suggest boas also hunt in coordinated packs, gathering at the mouth of a cave to gobble bats leaving their roost.)

The Cuban tody is found only on Cuba and surrounding islands. (Katherine Frey/The Washington Post)

Tolson sees no hutias in the trees, but he does spy a muscular leg dangling from a branch about six feet high. It belongs to a large Cuban rock iguana, from the genus Cyclura, one of 17 species on the Caribbean islands. They are among the most endangered lizard groups in the world, threatened by hunting, collecting, habitat destruction and introduced species. But not at Guantanamo, where the iguanas are everywhere — looking for handouts at the stairs to the beach, basking on mowed lawns and idling on rocks by the harbor. The base, Tolson says, is “a real gold mine of iguanas.”

The olive brown iguana on the branch is a gnarly beast, perhaps four feet long, and perfectly camouflaged. It has armored-looking skin draped over cartoonishly muscular shoulders and legs, a line of spines along its back and a menacing visage. It looks like a dinosaur, a relic from another era.

And it is. Like the boas and the hutias, the iguanas tell tales of evolution, which occurred as tectonic plates crashed and split, ice ages came and went, and sea levels rose and fell. The iguanas and boas evolved in the Caribbean over perhaps 30 million years; the hutias began their evolutionary journeys about 10 million years ago.

Yet as interesting as it may be to ponder the deep questions, such as evolution, Tolson says he’s driven by something much more basic in his snake studies: He’s simply enthralled with the boas, which live for decades and have elaborate weeks-long courtship rituals that belie preconceptions about coldblooded, reptilian behavior. The boas are “beautiful to look at, interesting to study,” Tolson says. “It’s an added benefit that they have such a unique and interesting evolutionary history.”

Though Cuban rock iguanas are found all over the base, they are threatened. (Katherine Frey/The Washington Post)

The legacy of science at Guantanamo dates back at least a century: In 1916, the oologist (egg collector) T.W. Richards wrote “Breeding of Tiaris canora, and Other Notes From the U.S. Naval Station, Guantanamo Bay, Cuba.” He included helpful tips for those who would follow in his footsteps, recommending flannel shirts (“nothing thinner will stand the thorns and prevent sunburn”), a straw hat and “stout laced shoes.”

Like anyone else, researchers need military clearance to visit, and public affairs officer Julie Ann Ripley says the military is generally supportive of the work. David Reed of the University of Florida has conducted studies on the effects of climate change on the gene flow of Caribbean bats. Virginia biologist Craig Downs has surveyed the coral reefs for the National Oceanic and Atmospheric Administration. And Allison Alberts of the San Diego Zoo has studied the iguanas, and other reptiles and amphibians.

Last year, reserve Navy Capt. Kristin Bakkegard, an associate professor of biological and environmental sciences at Samford University in Birmingham, Ala., was mobilized to Guantanamo. One day, while tracking boas with Tolson in her spare time, she photographed a lizard that looked a bit different.

A Cuban green anole’s dewlap is extended as a warning. These lizards are native to Cuba but have been introduced in Florida. (Katherine Frey/The Washington Post)

It turned out to be the Guantanamo striped curlytail lizard — a critically endangered species known from only seven individuals, three observed in 1973 and four in 2012, all spotted outside the base. After serving her reserve duty, Bakkegard secured a research grant to visit again and found a dozen lizards at two sites on the base. She is discussing the discovery at a conference this month.

Less-studied but important species on the base include West Indian manatees, American crocodiles, and green, hawksbill, leatherback and loggerhead sea turtles. Exotic endemic birds abound: large, furtive Cuban lizard-cuckoos; tiny, curious Cuban todys; elegant Cuban emerald hummingbirds; and pale blue Cuban gnatcatchers.

Temple University herpetologist S. Blair Hedges says the lack of hunting on the base gives it an abundance of iguanas and hutias he’s not seen elsewhere on the island. “It really is a sanctuary,” he says.

James Kraska of the U.S. Naval War College says that aside from the detention center there is little reason to maintain the base, and that Naval Air Station Key West can support most of the operations now performed at Guantanamo. For that reason, he and Joe Roman, a fellow at the University of Vermont’s Gund Institute for Environment, proposed in Science magazine last year that Guantanamo be transformed into a peace park and ecological research center. They envisioned a site “housing research and educational facilities dedicated to addressing climate change, ocean conservation and biodiversity loss.”

Reaction was mixed. Sen. James M. Inhofe (R-Okla.), senior member of the Senate Armed Services Committee, told Climatewire, “That’s the dumbest thing I ever heard.” (Peter Tolson also has opinions about the future of the base but is too diplomatic to put them on the record.)

While Roman had been hopeful during the Obama years, he’s less optimistic with the Trump administration , which just rolled back Obama-era steps to normalize diplomatic relations with Cuba. And long-standing military policy remains unchanged. In an emailed statement, Department of Defense spokesman Ben Sakrisson says, “The United States Government has no intention to alter the existing lease treaty and other arrangements related to Naval Station Guantanamo Bay, which enables the United States to enhance and preserve regional security.”

Still, Roman believes the proposal presents a third path between the Cuban demand to return the land immediately, which Raúl Castro reiterated to Obama during his Cuba visit in 2016, and the determination of the United States to hang on to the base. “It could be a good economic decision,” Roman says, because ceasing military operations would save millions of dollars. “It would certainly be a good ecological decision to protect the area, and it could be very good politically, both for normalization with Cuba and because most of the world agrees that that land should go back to Cuba.”

Tolson scours the 45-square-mile naval base in a Kawasaki Mule utility vehicle looking for the boas. (Katherine Frey/The Washington Post)

Late one morning, Tolson pulls his four-wheeler off the road near a small housing area called Tierra Kay, a.k.a. TK. More than a decade ago, a resident noticed a boa drinking the condensate dripping from an air conditioner. Tolson outfitted her with a radio transmitter and named her Tiki. He’s been tracking her for 14 years, the longest of any of the snakes in his study.

Tolson scans for the snake. He hears a signal, a staccato clicking, that gets stronger as he scrambles up a hillside and through tight, thorny shrubs. Homing in on the signal, Tolson says quietly, “I try to go around them as I zero in on them.” He’s moving slowly now, through knee-high grass.

The Cuban pygmy owl is endemic to the island. (Katherine Frey/The Washington Post)

“I think she’s right here,” he says, gesturing to an unremarkable patch of grass. He kneels and starts brushing the green grass aside to reveal a slightly bulging mat of dead grass beneath. He gingerly sweeps this away. And there is the snake. Even a glimpse of its flank shows that it is massive, somehow coiled up in a hollow in the grass.

“There she is. Beautiful. Oh, she’s big, too. Look at the size of her. See how she’s bulging out? She might’ve eaten a hutia,” he says. A few seconds pass, and the snake begins to move. “She’s taking off,” Tolson says.

The snake slowly inches away, its muscles rippling. Soon, the grass is waving eight feet away, downhill, even as the snake is still unfurling from its refuge. It pauses in a clear patch, and Tolson gets a good look. “She’s about 11 feet of beautifully patterned brown, chestnut and black patches,” he says. “She looks phenomenal.”

The snake stays still for a moment in the dappled shade. Mosquitoes drone, zenaida doves coo and traffic passes below, on the road to the detention center. Then the snake slides off into this strange piece of land, this American outpost in Cuba, as its ancestors have for millions of years.

Murray Carpenter is a freelance journalist and the author of “ Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks Us.

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