El Niño not good for dwindling leatherback sea turtles

Leatherback sea turtle closeup. Photo by Scott R. Benson, NMFS Southwest Fisheries Science Center.

Study suggests global warming will add to pressure on wide-ranging reptiles

By Summit Voice

SUMMIT COUNTY — Along with weather woes like droughts or excessive moisture, El Niño has been linked with higher mortality rates in populations of critically endangered leatherback sea turtles.

Those impacts could be exacerbated by global warming, may lead to more frequent warm and dry spells in key breeding areas like Northwest Costa Rica, according to researchers with Drexel University.

“Climate change may threaten survival of leatherback populations even if other factors driving population declines are removed,” the researchers wrote in a paper published online in the open access journal PLoS ONE.

El Niño Southern often results in dryer, warmer weather in northwest Costa Rica, conditions  associated with increased egg and hatchling mortality. Most climate models forecast that such conditions will become more common in the region over the next hundred years, which could significantly impact the already threatened leatherback turtle population.

The study found that the eggs and emerging hatchlings are sensitive to low precipitation and high temperatures, with hatching success tied to the precipitation totals in the two-month period leading up to egg laying, as well as precipitation in October (just before the dry season) and the average ambient temperature during the two-month incubation period.

Leatherback turtle populations were widespread in the tropics and subtropics, but their numbers have plummeted as a result of poaching and because the turtles often become entangled in fishing nets.

Population declines have been dramatic in the eastern Pacific, with Playa Grande, in  in northwestern Costa Rica remaining as one of the last breeding strongholds.

Leatherbacks are the most migratory and wide ranging of sea turtle species. They have built-in biological thermostats that enable them to maintain a core body temperature higher than that of the surrounding water, thereby allowing them to tolerate colder water temperatures.

Nesting female leatherbacks tagged in French Guiana have been found along the east coast of North America as far north as Newfoundland. Atlantic Canada supports one of the largest seasonal foraging populations of leatherbacks in the Atlantic. Leatherbacks tagged with satellite transmitters at sea off Nova Scotia were tracked to waters adjacent to nesting beaches along the northeast coast of South American, the Antilles, Panama and Costa Rica



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