“Another one!” someone shouts, pointing at a dark dot on the sea surface a couple hundred metres ahead of our boat. As we approach, a sea turtle unravels on the surface. The animal, apparently resting, is completely unaware of our presence. “It’s the third loggerhead today”says Frederic Vandeperre, a researcher from the University of the Azores who has dedicated its research to sea turtles. Before we could say anything else, the turtle realized it was not alone and vanished down into the deep blue, flapping its powerful fins. “That was a large one!”, says Vendeperre. “Shouldn’t take much longer until it goes back to Florida”, replies Christopher Pham, also researcher at the University of the Azores. 

An estimated 50 to 70 thousand annual spawnings of the loggerhead sea turtle (Caretta caretta) take place in the southeastern United States of America, particularly on the beaches of Florida. These numbers translate into approximately six to eight million eggs, assuming an average of 115 eggs per laying, making this region the largest nesting area in the Atlantic, and possibly the world. 

After approximately two months of incubation in a nest dug by the mother, a few centimetres below the surface of the sandy beaches, the small and restless turtles, not exceeding five centimetres of shell, emerge from the ground and rush towards the sea. A short but risky journey, proving lethal for many of them, unable to avoid the onslaught of sea birds, crabs, reptiles, and small mammals, which do not hesitate to grab an easy meal. The fastest, or luckiest ones, manage to reach the water where they have to overcome the surf zone through vigorous, albeit uncoordinated flapping of their small fins. They then disappear into the immense blue, without looking back, with a promise to return one day. 

The moment the newborns enter the sea marks the beginning of a phase of oceanic life for these animals. A phase that will last until adulthood, and which, for many decades, was characterised by almost total ignorance. Nobody knew for sure where the individuals were going, what they were eating, how they interacted with their surroundings and what dangers they faced. It was as if they disappeared without a trace. The scientific community called this period “the lost years”. 

Faithfull to their promise, they would eventually return as adults, settling and becoming a regular presence in the coastal waters of the region they had left behind several years earlier. 

In the 18th and 19th centuries, scientists were struggling with another mystery, involving the same species of turtle, but on the opposite side of the Atlantic: its great abundance, particularly in the waters around the Azores archipelago. Reports date back to 1595, when the Dutch captain Van Linschoten, wrote in his navigation routes: “… when passing from 36° to 39 1/3°, you will spot the Island of Flores with many turtles floating in the water”. During oceanographic campaigns in the Azores region aboard the ships ‘Hirondelle’ and ‘Princess Alice’ in the 19th century, Prince Albert I of Monaco also published some observations of these animals in the region. In his notes, the prince suggested that their origin might be the West Indies or Florida and that the turtles travelled all the way from the western Atlantic through the Gulf Stream. In 1972, the Dutch zoologist Leo Brongersma published a remarkable study on European sea turtles, mentioning the large number of small individuals around the Azores and suggesting, for the first time, that the animals found in European waters originated from the nesting beaches of the western Atlantic. 

This theory could explain part of the mystery that had for so long kept American scientists awake at night. However, scientific evidence was needed to support it. According to Brongersma, such evidence could be achieved through the implementation of a turtle tagging programme that would allow to begin to understand their movements. 

This programme started in the Azores in 1982, promoted by the researcher Helen Rost Martins, from the Department of Oceanography and Fisheries (DOP) of the University of the Azores and the naturalist Dalberto Pombo. “One day, in a café in Madalena on Pico Island, I noticed a flyer from Pombo asking local fishers to look for tagged turtles,” says Martins. “I contacted him straight away.”