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CESTM coordinates the French Eastern Atlantic Marine Turtle Network and welcomes all marine turtles found stranded or in distress drifting or as accidental by-catch along the Channel & Atlantic coasts of France (from the Spanish border to the Belgian border). 220 of the turtles thus cared for have been released since 1988, and 23 were fitted with Argos satellite telemetry PTTs since 2008.

Photo : Jupiter on its way to the ocean (Photo Aquarium La Rochelle SAS)

The Argos tracks of the turtles are different each time with a number of surprises. This enable to better understand the behavior of these endangered marine species once released from the French Atlantic coast, and determine what oceanographic parameters influence their movements.

Icare: “Bermuda, here I come!” (or… maybe not)

Icare (Photo Ré Nature Environnement)
Icare (Photo Ré Nature Environnement)

We already met with Icare a few months ago (see Understanding the tracking of three loggerhead turtles with ocean data). Icare is a young loggerhead turtle found stranded on a beach in Mimizan (South-West of France) in January 2018. This turtle is taken care of by the Centre d’Études et de Soins pour les Tortues Marines (CESTM ; Research and Cares Center for Sea Turtles) of the Aquarium La Rochelle.

The Loggerhead turtle (Caretta caretta) is a vulnerable species, protected at the international level. It lives in every temperate and tropical region of the Atlantic, Pacific, Indian Oceans and Mediterranean Sea, feeding on small fish, mollusks, jellyfish and crustaceans. It’s the only species of sea turtle that nests in temperate zones, every two to three years. Juvenile loggerheads (15 to 24 cm) are frequently stranded during the winter season on the French Atlantic coast because they experience cold-stunning, a debilitating lethargy that often leads to death with a long exposure to cold water. Since 1988, 220 loggerhead turtles have been received care at Aquarium La Rochelle’s CESTM.

Icare was given an Argos PTT just before it was released to the sea from a beach North of the Ré’s island (Charente-Maritime, Western France), equipped by the Centre d’Etudes et de Soins pour les Tortues Marines of the Aquarium La Rochelle. This turtle has now been monitored since June 29, 2018.

Studying his route, the CESTM notes that Icare made a great loop off the Azores archipelago between 24/10/2018 and 22/12/2018. This loggerhead turtle seemed to follow very precisely the boundary between two areas showing steep variations in sea level. These front areas are generally nutrient-rich. Since leaving the Azores area, Icare went a bit South, and made its route towards the Bermuda Islands at about 30°N in a more or less straight line.

Five species of marine turtles have been recorded in the Bermuda Islands. The loggerhead is not known to regularly inhabit the waters of the Bermuda Islands and its nesting activity is extremely rare.

Icare's track on April 14, 2020 overlaid on Sea Surface Heights (Argos tracks for CESTM/Aquarium La Rochelle, ADT data EU Marine Copernicus)
Icare’s track on April 14, 2020 overlaid on Sea Surface Heights (Argos tracks for CESTM/Aquarium La Rochelle, ADT data EU Marine Copernicus). See the Animation of Icare’s track overlaid on Sea Surface Heights (Animation CLS, Argos tracks for CESTM/Aquarium La Rochelle, data EU Marine Copernicus)

So why did Icare go towards Bermuda? These islands are positioned near the Sargasso Sea which offers a unique refuge to a host of open ocean species, including sea turtles. The Sargasso Sea is turning clockwise, driven by the Gulf Stream Current from the northwest and the Canaries Counter Current from the southeast. Icare probably followed the Canaries current and then the North Equatorial current, which reaches close to Bermuda Islands. These days, Icare seems to have had a change of heart, or maybe it is turning around an eddy… According to its capacity, Icare’s PTT will last 920 days. So, we hope to follow its incredible journey until January 2021, and thus learn where it will go. (To be cont’d!)

Jupiter may have gone too much North

Jupiter with an Argos PTT (Photo Aquarium La Rochelle SAS)
Jupiter with an Argos PTT (Photo Aquarium La Rochelle SAS)

On December 9 th, 2018, a Kemp’s ridley sea turtle (Lepidochelys kempii) was found grounded on the coast, about 50 km South of La Rochelle. This subadult individual, 56-cm long and weighing 21 kg, was brought to the Centre d’Etudes et de Soins pour les Tortues Marines (CESTM) of Aquarium La Rochelle to be cared for during 7 months. Kemp’s ridley sea turtle is the smallest species of sea turtle (average size at adult stage: 65 cm), in critical danger of extinction according to the IUCN Red List.

Finding a subadult or an adult Kemp’s ridley sea turtle on the Eastern coasts of Atlantic is highly unusual. Most often, turtles of those ages are found within the Gulf of Mexico where they reproduce and where they adopt a mostly coastal behavior. Since CESTM activities began, only 27 Kemp’s ridley sea turtles were cared for, and only 8 of them survived and were released afterwards.


Jupiter's track on October 23, 2019 overlaid on Sea Surface Temperature (Argos tracks for CESTM/Aquarium La Rochelle, SST data EU Marine Copernicus)
Jupiter’s track on October 23, 2019 overlaid on Sea Surface Temperature (Argos tracks for CESTM/Aquarium La Rochelle, SST data EU Marine Copernicus) See the Animation of Jupiter’s track overlaid on Sea Surface Temperature (Animation CLS, Argos tracks for CESTM/Aquarium La Rochelle, SST data EU Marine Copernicus)

On July 4 th, 2019, this turtle, nicknamed Jupiter was released from the same beach as Icare one year before. It began by swimming South, down to Spain, staying close to the coast all the time, for about three weeks. Then on July 24 th, it began migrating North. It toured the Brittany peninsula, and entered the English Channel in August. It went along both French and English coasts, crossing the Channel twice. Once in the North Sea in late September it went along the Belgian, Dutch, German and Danish coasts. Between October 25th and November 3rd, it was even located in the Skagerrak, the strait between Denmark and Norway. It continued to travel North, but its PTT stopped working at 58.6°N, on November 20th, 2019, after 140 days, nearly 4,000 km and 9 countries crossed.

Our hypothesis is that it followed a « warm » tongue of water that far North. However, when it receded with Autumn, Jupiter did not go back South, while the water temperature dropped to less than 10°C. Then, it’s possible that Jupiter suffered from cold-stunning, this is what happens unfortunately to marine turtles that stay a long period in cold water.


References and links


One of the tracked birds, named EH, at Pak Thale, Thailand, 14 November 2019 (Credit Ayuwat (Ton) Jearwattanakanok)

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A bowhead whale (cropped from Kit Kovacs/Norwegian Polar Institute)

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Two dorcas gazelles (credit C Enseñat)

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An Olive Ridley turtle with an Argos PTT glued on its back. The glue is made so as to fall off within one year (credit Katsufumi Sato, University of Tokyo)

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Olive Ridley sea turtles live in the tropical oceans. They dive to feed, and, as all species of sea turtles, they are threatened these days. To help in understanding and protecting them, some are tracked using Argos satellite telemetry. However, the environmental data thus collected can help other fields of…
first message from Argos beacon

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The first ARGOS satellite dedicated to environmental monitoring was launched in 1978 by NASA. Since then, this system has been at the service of the international scientific community and has enabled a better understanding of our Earth, its fauna, climate, meteorology, etc. Some scientists even say…
A silky shark with a pop-up tag (Credit NOAA Fisheries)

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Silky sharks occupy the same habitat as some marketable tuna species, thus leading to high risks of bycatch by fisheries. A NOAA study using a combination of telemetry technologies, including Argos satellite telemetry, aims to identify potential patterns in silky shark behavior in order to devise effective bycatch mitigation strategies.
ANGELS Kinéis nanosatellite

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On December 18, 2019, the French Space Agency, CNES, has launched the first Argos nanosatellite, marking the beginning of a revolution in the Argos system as we know it. This nanosat is the prototype mission for Kinéis, a constellation of 25 nanosatellites with Argos…
Photo: A lesser kestrel with an Argos PTT (Green Balkans)

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National Geographic “Sea to Source Expedition.” Photo copyright Alasdair Davies

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Weddell seals are the most southerly breeding mammal species. They are found among other places in the Weddell Sea, but their behaviour and foraging strategies are not well-known, in an area itself largely unknown. Scientists at the Alfred Wegener Institut tracked them using Argos PTTs recording…
a porcupine crab with its harness (Credit University of Windsor)

29.11.2019 Animal tracking applications Deep-sea crabs tracked with Argos!

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Male black caiman with an Argos satellite transmitter glued to its head (photo S Caut)

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Crocodilians are tropical wetland ecosystems’ top predators, but they are rarely studied. Black caimans, which live between Central America and the northern part of South America, saw their population drop by 90 % in the 20th century. To have a better understanding of their behavior, scientists used Argos PTTs to track…
great spotted cuckoo iStock

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Cuckoos’ most well-known characteristic is the laying of their eggs in another species’ nest taking advantage of the care provided by these foster parents (brood parasitism). But some cuckoo species, such as great spotted cuckoos, are also migratory. Advancements in Argos satellite telemetry – especially miniaturization of Argos tags –…
Saimaa ringed seal tagged with a GPS-Argos tag (Wildlife Computers, USA), photo: Saimaa ringed seal research UEF.

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Ringed seals are living during winters in ice covered environment, both sea and lakes. One of the subspecies is living around Lake Saimaa in Southeastern Finland, where human activities are restricting their living areas and the population is endangered. The University of Eastern Finland has studied their movement using telemetry…
Record-breaking animals

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New Argos tracking study by the Norwegian Polar Institute and the Norwegian Institute for Nature Research (NINA) reveals unimagined distances traveled by a female Arctic fox, from Svalbard to a remote part of Canada. In the Southern hemisphere, an Oriental pratincole, tracked by the Australasian Wader Studies Group, surprises scientists…
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For 15 years, Kelonia, the CEDTM and its partners (Ifremer, CNRS, Universities, TAAF, the French Biodiversity Agency-AFB,…) have equipped nearly 300 sea turtles with Argos tags to study their movements in the Indian Ocean – from the high seas to coastal waters. Their research has resulted in knowledge and understanding…
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Carrion birds in general, and especially the largest of them are often threatened species, even though they are providing huge ecological services. The California condors among them nearly disappeared. They are now recovering thanks to reintroduction efforts, but are still endangered, especially by lead poisoning. Pinnacles National Park and Ventana…
pegase2019 sasemar

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An Argos ocean buoy deployed off the coast of Banyuls, France, in May 2019, has been visiting the Spanish coastline – along with approximately 30 million tourists this summer. The buoy, deployed within the French Space Agency’s Argonautica project, in collaboration with students and teachers from the Lycée…
An Oriental Pratincole with an Argos PTT antenna (Credit: Subbu Subramanya )

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Oriental Pratincoles, Australia’s most numerous shorebird, spend up to three months in Australia, migrating to various parts of Asia to breed. To date, traditional marking using bands and flags has produced little insight into their destinations & migration paths. Using 2 g Argos satellite telemetry tags, their migration is monitored…
Humpback whale and tag (Credit University of Auckland)

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Humpback whales are long-range migrators, on the recovery after heavy whaling during more than 150 years. Understanding where they feed in the polar oceans, and why they might choose an area rather than another is helped by Argos telemetry tracking. Populations recovering from whaling, but not the same everywhere…
Arctic Fox

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Arctic foxes are living in all the regions around the Arctic ocean. Argos satellite telemetry tracking demonstrates that some of those foxes are changing continent using the sea ice as bridge, travelling thousands of kilometers in a few months in the process, from Svalbard to Canada. ‘Recordfox’ of distance Since…
A whooping crane with an Argos PTT on its right leg (Credit Louisiana Department of Wildlife and Fisheries)

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Whooping cranes were nearly extinct in North Americas in the 1950s. Preservation actions initiated since then have enabled the protection of the species. Reintroduction programs, helped by Argos satellite telemetry are now increasing the populations, and enabling new discoveries on those emblematic birds. Whooping Cranes (Grus americana) are large birds…
Group of Mhorr gazelle with a GPS collar (credits T. Abáigar)

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The Mhorr gazelle is an endangered species of the Sahelian area. It is one of the most singular, threatened and scarcely-studied gazelle species of northern Africa. It is considered by locals as part of their cultural wealth. Reintroduction into the wild of captivity-bred individuals has first been tried in Southern…
IMOS glider

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On June 16th, people around the world celebrate the beauty of sea turtles and their importance to the marine ecosystem. CLS, unique operator of the Argos system since 1986, would like to take this occasion to honor the scientists working to understand and protect sea turtles globally.  The Argos system…
loggerhead turtle

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fiordland crested penguin

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An elephant seal track (CEBC/CNRS), with the elephant turning around the low eddy on the right (sea level anomaly map dating from that turn)

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Argonautica annual meeting 2019 (photo A. Willm for Cnes)

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