Biologging: tracking animals to understand the sea

Just over a year ago, on 5 October 2025, Thalassa returned to the sea.

A loggerhead sea turtle (Caretta caretta), she had arrived at the Genoa Aquarium to receive the necessary care before being returned to her natural environment. But on that occasion, thanks to a collaboration with Fondazione CIMA and technical support from the University of Pisa, her return to the sea had something extra: Thalassa carried a small satellite tag, a device capable of turning data on her movements into new information about her behaviour at sea and the surrounding ecosystem.

Exactly one year later, the story is repeating itself. Angela and Lisa, two loggerhead sea turtles (Caretta caretta) that arrived at the Genoa Aquarium Rescue Centre in recent months, have returned to the sea after recovering to good health. Like Thalassa, Angela has been fitted with a satellite tag that will make it possible to track her movements and collect valuable data on the environment through which she travels.

Because that small device offers much more than the ability to know where a turtle is: it provides a different way of observing the sea.

The sea seen through animals

Biologging is a monitoring approach that uses small devices, known as tags, attached to animals to collect data on their behaviour and movements, such as movement speed and acceleration, as well as information on the environmental conditions around them.

Joint analysis of these data makes it possible to relate animal movements and behaviour to the characteristics of the environments they move through. Researchers can therefore investigate, for example, how animals use space, which areas they frequent, and how they modify their behaviour in response to different environmental conditions.

Biologging therefore does more than simply track an animal's movements on a map: it provides data that help us understand its ecology and habitat use. At the same time, measurements collected along the animal's path can contribute to our knowledge of the marine environment by providing observations directly associated with the locations and conditions in which the animal lives and moves.

Not all tags collect the same data

Biologging encompasses a range of instruments designed to address different research questions.

Satellite tags, such as those used on Thalassa and Angela, collect data that are compressed and transmitted to satellites or ground-based receiving stations. They are attached to the animals and can remain in place for weeks or months. They are therefore suitable for long-term monitoring, although the data they provide have lower resolution.

Archival tags , by contrast, are attached using suction cups. They can be equipped with additional instruments such as hydrophones or video cameras and record much larger volumes of data, which are stored in the device's memory. The tag must then be recovered after it detaches from the animal in order to retrieve the data. In this case, the monitoring period is shorter, but the data resolution is considerably higher.

Not just turtles

The collaboration with the Genoa Aquarium is part of a broader biologging research programme that Fondazione CIMA has been pursuing for several years.

The monitoring programme using these instruments began in 2021 with the GIAS project (funded under the 2014-2020 Interreg Italy-France Maritime Programme), whose main objective was to prevent risks to navigation. It was within this framework that tracking data for goose-beaked whale were obtained in the Mediterranean for the first time.

Since then, biologging has been extended to other projects and research questions: from the issue of sperm whale entanglement in fishing nets, addressed by the Reduce project, to the analysis of cetaceans' exposure and behavioural responses to vessel traffic within the SEAsteMAR project, and the improvement of models describing ocean currents through the deployment of tags on animal carcasses.

The collaboration with the Genoa Aquarium has added sea turtles to these monitoring activities, broadening the range of marine megafauna being observed and expanding research opportunities.

And so, as Angela returns to swimming in the Mediterranean, the small device on her carapace begins to tell part of her story: where she travels, which environments she moves through, and the conditions she encounters.

One year after Thalassa, another turtle brings with her the opportunity to view the sea from a different perspective: that of an animal that moves through it every day.