Mystères des bas-fonds

Le Groupe de travail sur la tortue luth.

La tortue luth peut avoir les dimensions d’un lit double et peut peser près d’une tonne. Elle peut plonger plus d’un kilomètre sous l’eau et maintenir une température corporelle jusqu’à 18 degrés C au-delà de la température de l’eau ambiante. Elle naît en Amérique du Sud et en Amérique Centrale et ne mange que des méduses. Une portion de la population des tortues luth, qui est en déclin de façon alarmante, passe l'été à proximité des côtes de la Nouvelle-Écosse.
La tortue luth est le plus gros reptile du monde.

« Ce n’est qu’à partir des années soixante que des chercheurs ont commencé à documenter la présence de la tortue luth ici ; et même à ce moment personne n’avait fait d’études approfondies sur elle », constate Mike James, coordinateur du Groupe de travail sur la tortue luth, un groupe qui veut en apprendre d’avantage sur la tortue et sur ses déplacements dans les eaux de la Nouvelle-Écosse.

 

 

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Mystery of the Deeps

 

    Kathleen Martin,
    For the Leatherback Sea Turtle Working Group
    October 1998

 

t.gif (259 bytes) hey can grow to the size of a double bed and weigh up to a ton. They can dive more than a kilometer into the sea, and they maintain body temperatures as high as 18 degrees C. above the surrounding water temperature. They eat only jelly fish. They are born in South and Central America, and a portion of their declining population spends the summer off the coast of Nova Scotia. The leatherback turtle is the world’s largest reptile, and one of it’s most mysterious.

turtle2.jpg (29210 bytes)
(photo: Vern Skalpsky, North Atlantic Leatherback Turtle Working Group)

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Female leatherback nesting on Trinidad Beach
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"We know very little about the basic biology of leatherbacks – their growth rates, their reproductive behavior, their life span," says Mike James, Coordinator of the Leatherback Sea Turtle Working Group, which is interested in finding out more about the turtles, including their distribution in Nova Scotian waters. "We don’t fully understand their ocean travel routes, and we have no idea where in the open ocean the juvenile leatherbacks are. There are no records of small leatherbacks at sea."

"Researchers only began documenting the leatherbacks’ presence here in the 1960’s, and even then nobody did in-depth studies on the turtles," says James. "Fishermen have always known that leatherbacks are part of the marine environment in Atlantic Canada, but nobody has asked them to contribute to research on the animal until now."

The Leatherback Sea Turtle Working Group depends on information from fishermen, because they encounter the animals more than anyone else. James has spent the last five months travelling throughout coastal communities in Nova Scotia talking to fishermen about leatherbacks, as well as to school children and operators of whale and seabird tour boats. The contacts he has made so far have been encouraging. Not only have many people volunteered to help with the project, but many have also reported past sightings.

turtle1.jpg (18334 bytes)
(photo: Lindsay Hatcher, North Atlantic Leatherback Turtle Group)
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Adult turtle  (swimming off Cape Breton, N.S.,
August 1998)
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One thing he learned was that there were a large number of leatherbacks feeding in Shelburne Harbour last August. "That kind of phenomenon has only been documented a few times for this species," says James enthusiastically, "and it occurred here. That’s significant. It’s possible that there were more leatherbacks off Shelburne last year over the course of three days than we had previously thought would come to the province in a year."

Biologists used to think leatherbacks found in Nova Scotian waters were individuals that had strayed from their southern habitat as they followed the Gulf Stream in search of jellyfish. "But we now believe that isn’t so," explains James. "The animals that are here mean to be here, because they know they can find lots of jellyfish here. And the turtles are here every year. But apart from knowing that leatherbacks eat jellyfish, we still know very little of their habits in the North Atlantic."

The number of leatherbacks that come to Nova Scotia, and where precisely they go when they get here, is so far unknown, but James is optimistic that the information he’s receiving this summer will help him begin to answer these questions. "We’ve recorded 34 new leatherback sightings already, and it’s only July," he says excitedly. "It’s August that’s the peak leatherback month in our waters."

James attributes a large part of the Leatherback Sea Turtle Working Group’s current success to people who have volunteered to put up its distinctive blue-and-yellow, "Have You Seen This Turtle?" posters across the province, and to those who have gotten the word out to people in coastal communities. The Working Group is interested in all sightings of leatherbacks, alive or dead. Anyone who has seen one should record the date, time, and location of the sighting as precisely as possible, the sea and weather conditions at the time, and , if possible, the water temperature. The Group would also appreciate any photos that might be taken of the turtles.

To report a leatherback sighting, or if you are interested in taking part in or learning more about any aspect of the project, please call Mike James toll-free, at 1-888-729-4667.

http://www.seaturtle.ca