Posts Tagged ‘marine defaunation’

Caring for Kemp’s Ridley Sea Turtle

Wednesday, January 28th, 2015

Sea turtles are endangered for all the reasons you might imagine, including pollution, plastics, propellers, nest destruction, egg poaching, disease, global warming, and bycatch from trawls, seines and long-lines. Through a lot of effort over the past 3-4 decades, their crash toward extinction has been slowed, and in some places some recovery has occurred – of course not to past population sizes, but at least away from the brink.

Kemp's Ridley Sea Turtle, the smallest of sea turtles,  lives mostly in the Gulf of Mexico, reaches sexually maturity at 10-15 years old (marinelife.about.com)

Kemp’s Ridley Sea Turtle, the smallest of sea turtles, lives mostly in the Gulf of Mexico, reaches sexually maturity at 10-15 years old (marinelife.about.com)

Kemp’s Ridley Sea Turtles may have come the closest to extinction. They mostly live in inshore waters in the Gulf of Mexico where they forage for crabs. For a long time no one seemed to know where they nested, but in the mid 1940s a single nesting beach on the Mexican coast, Playa de Rancho Nuevo, was discovered. There possibly 120,000 females hauled themselves up the beach over a period of several days, dug their nests and laid their eggs, an extraordinary and tumultuous event we call an ‘arribada’. Several arribadas appear to have occurred on that one beach each summer, the same females returning to lay more eggs.

Females come ashore in large numbers over a few days, an arribada. Arribadas occur several times during the summer, involving the same renesting females (noaa.com)

Females come ashore in large numbers over a few days, an arribada. Arribadas occur several times during the summer, involving the same renesting females (noaa.com)

We know now that females nest every second year, so the total adult population at that time must have been about half a million. The beach was so crowded that females arriving on the second or third day often inadvertently dug up and destroyed the eggs of their predecessors as they scooped out holes to lay their own eggs.

Though the arribadas were unknown to biologists until then, they were certainly well known to people living along that coast who quickly dug up most of the nests and distributed the eggs among the coastal communities. Those were not the days of regulations.

Kemp’s Ridley Sea Turtle numbers plunged. Though protected by the US Endangered Species Act in 1970, only 700 females arrived to nest in the summer of 1985. But the arribada beach became tightly protected and monitored; many nests were moved to concentrated sites where they could be watched more easily; other nests were dug up, their eggs transplanted to other beaches along the Texas coast, hatchlings allowed to crawl to the surf, then recaptured and raised in captivity for 9-11 months to plate-sized juveniles, and then released in the Gulf of Mexico.

By 2010 about 7000 females once again nested, not just on the arribada beach, but also in small numbers where the eggs had been translocated. Not the numbers of the 1940s, but enough to think recovery was underway. A rare success, it was the result of huge coordinated effort by untold numbers of volunteers as well as biologists, communities, and government agencies from two countries.

Numbers of nests on the arribada beach in Mexico increased remarkably after prolonged efforts to protect the beach (esasuccess.net)

Numbers of nests on the arribada beach in Mexico increased remarkably after prolonged efforts to protect the beach (esasuccess.net)

Transplants of eggs to Texas beaches began in 1978. Now there are about 200 nests scattered among a number of protected beaches (esasuccess.org)

Transplants of eggs to Texas beaches began in 1978. Now there are about 200 nests scattered among a number of protected beaches (esasuccess.org)

Since 2010, things have not been so good. The BP oil spill damaged the main foraging region along the north shore of the Gulf, oiling and killing around 5000 of the foraging turtles. Causal or not, nesting numbers flatlined and now have declined despite all the efforts to protect them: in 2014 only 11500 nests were counted, indicating a drop to around 3-4000 nesting females and so an adult population of about 12,000.

Number of nests increased impressively until 2010, but not since (seaturtles.org)

Number of nests increased impressively until 2010, but not since (seaturtles.org)

To complicate the picture, many juveniles drift and swim out of the Gulf and head north with the Gulf Stream along the East Coast. Some of them reach Cape Cod Bay and even further into the Gulf of Maine, a risky venture since at sea temperatures less than 17-18 degrees C (65 degrees F), they are stunned and tend to die if they are not somehow soon rescued and warmed up again.

Until recently, each autumn only a few washed up stunned on the beaches of Cape Cod Bay where searching volunteers found them, warmed them up, and sent survivors back to Florida often through informal connections with air pilots. But this past autumn more than 1200 stunned juveniles washed up on those beaches, swamping local abilities to recover and transport them back south. Many more volunteers became involved, searching the beaches through the autumn months; stunned turtles were sent to a wide assortment of aquariums to recover them; transporting them back to the Gulf of Mexico was much more challenging.

Two no longer stunned  juveniles getting ready to travel back to the Gulf of Mexico

Two no longer stunned juveniles getting ready to travel back to the Gulf of Mexico

Once again, this has involved a huge labor-intensive and expensive effort by volunteers, biologists, and government agencies.

Now with declining numbers of nesting females and increasing numbers of stunned juveniles, we are nagged by the question of whether all the effort is making a difference. Comparable efforts of course struggle to protect and conserve the other species of sea turtles as well. They all remain endangered.

The case of Kemp’s Ridley Sea Turtles though is not reassuring. It has involved such huge effort to protect one species, with every conservation ingredient one could hope for. People truly care, and still recovery may fail, and fail because we cannot protect the animals from catastrophic oil spills or from the increasing and unpredictable stresses of climate change.

Hatchlings rush to water's edge. Much effort has been invested to help Kemps Ridley Sea Turtles recover, but has it been effective? (seathos.org)

Hatchlings rush to the water’s edge. Much effort has been invested to help Kemps Ridley Sea Turtles recover, but has it been effective? (seathos.org)

Though few marine species, including seabirds, marine mammals, fish, shellfish and other invertebrates have actually been reduced to extinction, population sizes of so many of them have declined precipitously, and local extinctions are common.

As a recent major review of marine ‘defaunation’ establishes, we are on the cusp of developing inshore waters in the ways we have developed terrestrial ecosystems over the past few millennia, development that has resulted in the extinction of so many terrestrial species. The review concludes that although much damage has already occurred, it is not too late to prevent marine extinctions on a similar scale – through protected areas, enlightened management and careful development.

But there is so much that is threatened, even in the rosiest of scenarios. We have hard choices ahead. How do we decide how much effort to invest in trying to recover one species, like Kemp’s Ridley Sea Turtle, when whole communities and ecosystems are at risk? Can somehow we protect both?

Either way, our energetic and global effort is essential.
And a world without sea turtles is a world immeasurably reduced.