Kemp's Ridley turtles saved by science?
Kemp's Ridley turtles, Lepidochelys kempii, are critically endangered. Anything which makes any effect on their survival is welcome to every one of us. There is a similar model of green turtles available but this paper concentrates on the Caribbean dispersal, from the western Gulf, of young Kemp's Ridley. 94% hatch from the beaches of Tamaulipas in Mexico. Nathan F. Putman of Oregon State University and colleagues from the US and France put together models that could explain how we should locate the youngsters as they travel through the Sea during their most vulnerable stages.
In their oceanic phase, animals such as turtles are almost impossible to trace for 2-15 years. Instead, the technique sis to use passive particle dispersal models because the tiny slow-swimming animal is in effect totally passive as it is swept along by complex currents. The nesting beaches are well-known and females always return there, so the "seeding" of the individuals can be realistically recreated.
From 2003-2010, counts of the annual cohorts of L.kempii were used to simulate their release in June, July and August into the Caribbean model. A "frenzy period" of swimming normally takes the youngsters to the open sea, or alternatively to "bounce off a neighbouring coastline! The articles were more numerous than the rare turtle, s it was relatively easy to draw average results for estimates such as age structure of a group within part of the model.
When Nathan and his co-workers examined the results, the whole Gulf and the NW Atlantic became the scenario. With the natal beach area still important for such young creatures, half had escaped their childhood homes and penetrated as far as the Florida Keys after their first, nursery year, with occasions when there was a rapid movement eastwards and completely out of the Caribbean. Such prediction fills a big gap in our knowledge. They are confirmed by the sparse in situ observations such as numerous early strandings and the occurrence of 38 in the Sargasso sea community on the West Florida Shelf.
The latter had an average carapace length of 233mm. 18 months is therefore the likely age of the cohort, if they were from the same group of drifting hatchlings. Survival there would be a lot easier than many other areas which they could have been swept to. Anthropogenic effects such as the frequent oil spills in certain areas and environmental factors need now to be quantified to give us some idea how to maintain a population of these precious reptiles.
According to the models, 2007 gave us a good year, with a great survival rate of >20%, the emergence of large numbers into the western Atlantic Ocean and the South American coasts well-covered! Maybe records can confirm some of that projected success, too, and please the authors.They publish, "Predicting the distribution of Kemp's Ridley sea turtles," in the Proceedings of the Royal Society B: Biological Sciences.
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