Loggerhead Turtles and  Galápagos Tortoises Avoiding Extinction

"One if by land, two if by sea!" Coined by Longfellow, in his poem about the iconic ride of Paul Revere, the warning referenced how many more British troops could attack by sea versus land. Coincidentally enough, in the natural world it appears that the Loggerhead sea turtles outnumber the Galápagos land tortoises. Today it is estimated there are approximately 40-50,000 nesting female Loggerheads who spend the majority of the life at sea. On the other hand, researchers suggests there are only 500 estimated tortoises currently living on the island.

Does that mean staying put on terra firms in one location is more risky than traveling an epic 8,000-mile solo journey around the North Atlantic basin?

Magnetic Map

Oddly, young loggerheads survive their migrations by staying at sea most of their lives. All toll, it takes them about 6 to 12 years to reach a formidable size that allows them to ward off their predators.

The migrations of young loggerhead turtles take them into the relative safety of the open ocean where predators are less abundant than in coastal waters. Their journeys are among the longest and most spectacular in the animal kingdom. The turtles begin as utterly defenseless, two-inch-long hatchlings — where the odds are initially stacked heavily against them.

Born with an inherited "magnetic map" they are innately aware of of the safest routes to take. Differences in magnetic fields at different locations cause the turtles to change course, while traversing these long distances.

For example, young loggerheads respond to a particular magnetic field near northern Portugal by turning south. This response helps them stay in warm waters and avoid being swept north into frigid waters near Great Britain and Scandinavia, where they would most likely freeze to death.

As far as possible extinction, the greatest threat to the loggerheads are their loss of nesting habitat due to coastal development, hurricanes, and human intervention.

According to the Sea Turtle Conservancy's latest forecasts, there are currently 40-50,000 nesting females in existence today, compared to 28,857 in 2007.

Back on the  Galapagos Islands

Now, the tortoises on the island of Galapogos are another story. A century ago, they were declared on the brink of extinction. However, just recently a small group of the tiny, shelled youngsters have been spotted. "I'm amazed that the tortoises gave us the opportunity to make up for our mistakes after so long," told researcher James Gibbs to The Dodo. who was among the first to see the hatchlings this past December.

When sailors first landed on Pinzón Island in the mid-18th century, they inadvertently triggered an environmental catastrophe that virtually took generations to correct. Rats aboard those early vessels quickly gained a foothold on the fragile ecosystem, feasting on the eggs and hatchlings of the island's tortoises who, up until then had very few natural predators.

The rats were so devastating, in fact, that over the following decades, minimal tortoise offspring survived the onslaught - setting the species on the path to extinction.

But just as human activity nearly spelled doom for the imperiled animals, it also helped them rise like a phoenix.

In 2012, biologists used helicopters to distribute poison specifically designed to kill rats. It was a first-of-its-kind use -- and it worked. Pinzón is now declared rat-free.

"The incredible eradication of rats on this island, done by the park service and others, has created the opportunity for the tortoises to breed for the first time," says Gibbs.

We did a survey to see if it was working for the tortoises. It was then they found 10 new hatchlings. This was the first time they've bred in the wild in more than a century," noted Gibbs.

Gibbs and his team spotted 300 tortoises in all on the trip, which he says suggests that there are may be more than 500 currently alive on the island. Talk about coming to the razor's edge of vanishing from the earth -- this remarkable case study shows that there are ways to combat extinction. Hopefully it will be the model for other such species surviving from the brink.

Primary Source:  The Dodo

 

 

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