It is one of the prettiest boat trips in Central America: up the mangrove canals north from the Costa Rican port town of Limon to Tortuguero National Park.

Sea turtle like this leather-back (top) give Costa Rica’s Tortuguero its name. The surrounding area boasts a national park and mangrove canals (below), while Tortuguero church (bottom) is one of the village’s own attractions.

The tannin-stained water is smooth as brown glass and mirror-calm, broken only by flotillas of drifting water hyacinth and the occasional swirl of fish or a cayman’s tail.

The banks are lined with palms and rain forest, mangroves (of course), stilt houses and the occasional wonky jetty.

Sloths move so slowly that moss and lichens actually grow on their skin. By contrast, spider monkeys and howler monkeys, the New World’s heaviest (and noisiest) primates, scrabble and swing and mock-charge boats that get too close to the canal banks.

They howl, too, hence the name.

Actually it’s more of a roar, and if you didn’t know what was making the dragonlike bedlam, you’d probably run like hell. If they’re in good form, they can be heard more than 6 km away.

Like the Nicaraguan coast further north, this part of Costa Rica is a water-based society with few roads. Indeed, given that Tortuguero receives some of the highest annual rainfall in the world (more than 5 meters per year), what roads there are are frequently indistinguishable from the rivers.

Instead of cars, people rely on boats and manmade canals that link natural watercourses and lagoons. These form a network of tropical waterways that enable locals and visitors to travel as far as the Nicaraguan border and beyond, without having to venture out into the turbulent Caribbean.

Nowhere here is far from the Caribbean, though. For parts of the journey, the sound of its breaking, angry surf can clearly be heard. This said, the mangroves and thin spits of land that separate the canal from the sea ensure a totally placid ride.

River traffic, particularly before entering Tortuguero National Park proper, is a busy and colorful, occasionally criminal, mix of canoes and flat-bottomed boats known as lanchas, piled high with anything, from fish traps, pigs and coconut crates to illegally cut tropical timber and concealed sacks of poached sea turtles.

It is the turtles that give Tortuguero its name (tortuga is Spanish for turtle).

And although Tortuguero offers visitors the opportunity of exploring the mangrove canals and hiking through rain forest, encountering anything from poison-arrow-dart frogs to tapirs, it is the turtles that are the principal tourist draw.

Tortuguero was first put on the world map by American sea-turtle researcher, Archie Carr. He set himself the task of finding out where green turtles (Chelonia Mydas) nest in the Caribbean.

The quest took him all over the region and is recounted in his thoroughly recommendable book “The Windward Road.”

Eventually he found what he was looking for: Tortuguero, the largest green-turtle rookery in the Caribbean.

In 1954, Carr founded the world’s first sea-turtle conservation organization, the Caribbean Conservation Corporation. As a result of CCC’s work, Tortuguero was gazetted a national park in 1970. CCC is still active in Tortuguero.

In fact, some say it is the world’s premier sea-turtle research organization, and CCC’s biological field station here hosts hundreds of scientists, students and volunteers each year.

The CCC studies loggerhead turtles (Caretta caretta) and the gigantic 3-meter leatherback (Dermochelys coriacea), although the focus of their research is the green turtle.

Green sea turtles aren’t particularly green. The ones off Peru are sometimes white. The ones off Hawaii are black. Their fat, though, is greenish. Along with cartilage called calipee scraped from inside the shell, the fat is a prime constituent of turtle soup.

One of Carr’s greatest sacrifices, apparently, was giving up eating turtle soup which is allegedly unparalleled in the deliciousnes of its flavor.

Vast herds of green turtles, numbering in the millions, once grazed the sea-grass beds of the Caribbean. Human exploitation of the turtles for food changed all that. Sailors discovered that the turtles, if occasionally sprinkled with water, could survive long periods stored in the hold and provide fresh meat, even a month after capture. Due to the low-protein content of marine vegetation — its main food — the animal’s growth is slow. It can take 20 to 50 years before the green turtle reaches sexual maturity, making populations especially vulnerable to hunting. Turtle eggs, too, although having no more nutritional value than a chicken’s egg, came to be regarded as an aphrodisiac. They are particularly easy to locate — just by looking for distinctive turtle tracks in the sand. These invariably point the way to the nest.

As the 20th century drew to a close, the herds of millions had become mere scattered thousands, and the green turtle, like every other of the eight recognized sea-turtle species , was placed on the endangered species list.

Despite CCC’s efforts, poaching for both meat and eggs persists even in Tortuguero National Park. The nesting beach is 38 km long. CCC conducts night patrols and, whenever possible, obscures telltale tracks. Some volunteers even construct fake raided nests to discourage poachers. It works. A bit.

Perhaps 80 percent of eggs, though, are still stolen.

CCC, in partnership with the National Parks Service, is currently conducting an outreach program for local people, training folk who might otherwise drift into poaching as turtle-watching guides. Near the small village of Tortuguero, with its pretty church and friendly inhabitants, is a curious geological feature, Cerro Tortuguero, a volcanic finger that rises sharply from the otherwise flat land.

According to local legend, this holds a cave in which there is a turtle-shaped stone called “Turtle Mother.” This rock allegedly turns inland when the sea turtles are due to arrive and turns out to face the sea when it is time for the hatchlings to leave.

Whether it will still be turning in a hundred years’ time is, unfortunately, impossible to say. Despite the efforts of CCC, the fate of Tortuguero’s most famous inhabitants still hangs very much in the balance.

In line with COVID-19 guidelines, the government is strongly requesting that residents and visitors exercise caution if they choose to visit bars, restaurants, music venues and other public spaces.