Tuesdays with Turtles – Navigation

Byoliveridley

If you did not know already, sea turtles tend to nest on (or close to) the beaches they were born at. It is known that they use the Earth’s magnetic fields to navigate. Here’s an article on the navigational natations (I strain to alliterate at times, but natation means swimming!) of the Green Turtle.

ScienceDaily: How Do Marine Turtles Return To The Same Beach To Lay Their Eggs?

I flagged this article not because it tells us much new, but just adds some nuances to sea turtle navigation.

The study has shown that the marine turtles’ navigation system allows them to maintain their course towards the egg-laying site wherever they find themselves. It is almost as if they were equipped with a compass pointing towards the beach in question. So they can correct any deflection they are subject to: transport by boat, ocean currents… But, unlike human navigators, they are not able to correct for ocean drift in plotting their course. So the movements recorded by the satellite are a combination of deliberate action by the turtles and the effect of currents. So it appears that the turtles’ navigation system is relatively simple and may cause them to be wander at sea for long periods during adverse ocean conditions. One turtle released 250 km from its egg-laying site on Europa traveled more than 3 500 km in two months before returning there!

Well, that’s interesting, if not surprising. It’s one thing to have a magnetic bookmark of a destination in your head (pretty wonderful thing, I wish I had it!) and swim continually towards this destination. It’s quite another thing to keep track of complex parameters like ocean drift and keep correcting continuously.

In essence, what they’re saying is that turtles home in on their destinations, but don’t always take the shortest way in because they tend to drift and not correct for this drift dynamically. It is not evolutionarily necessary because turtles probably do not get thrown way of course often enough that evolving even more sophisticated navigational systems (Garmin?) would provide a significant enough survival advantage.

In the Mozambique Channel, between the east coast of Africa and Madagascar, on the beaches of the French Islands of Europa and Mayotte, they caught turtles at the beginning of their egg-laying cycle, so that the animals were strongly impelled to return to this area to complete their cycle. After having Argos transmitters fitted to their shells in order to satellite track their return journey to the beach, the animals were released in open sea, several hundred kilometers from the egg-laying site.

Now that’s just mean! Imagine being kidnapped, tagged and released many miles away from home, and having to find your way back. Apparently, these turtles did it. Man, that would be such a cool navigational aid to have, quite a party trick!

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    Tuesdays with Turtles – Wednesday Hook Edition

    Byoliveridley

    WWF – Fishing Technology That’s Letting Turtles Off the Hook –

    Turns out that a small change in hook design can save a lot of turtles from getting caught in longline hooks. But the story’s not really about the shape of the hook. I’ve written about this before. The issue is rarely one of technology. The solutions have been developed and exist because a lot of work has gone into developing technological solutions. Implementation on the ground (or sea!) has lagged because it is much harder to effect change where it counts when you attempt to impose technology in a top-down fashion. Small scale fishers (new english here, to avoid the whole fishermen/fisherwoman/fisherperson nonsense, take out the gender specific suffix to every occupation describing verb! – Try it, it’s not weldman, or plumbwoman!) are in a world of hurt with declining fish stocks and widespread fisheries piracy by the so called “developed world”. Without developing and implementing the solution with the full participation of the people who have the most potential to be affected, the change will not be successful.

    What did the WWF do differently this time?

    Together with fishermen we are building a culture for sustainable fishing practices that will guarantee fish stocks in the long term

    They emphasized the people, not the solution. And the results were great, 90% reduction in turtle catch, >95% of the turtles caught were released safely, and the fish yields were not affected. Everyone wins, right?

    Good stuff. Those turtles are still endangered and we’ll run out of wild edible fish in 50 years, but hey, more like this and there’s a bit of hope.

  • Small-Scale Fisheries Bycatch Jeopardizes Loggerheads

    Byoliveridley

    35AA810F-45DF-436A-B609-5EF72D09CC9B.jpg

    This is almost a 1000 juveniles killed in a year in Baja California alone. The authors mention that over 99% of all fisherpeople are employed in small scale fisheries, which surprised me.

    PLoS ONE: Small-Scale Fisheries Bycatch Jeopardizes Endangered Pacific Loggerhead Turtles:

    Although bycatch of industrial-scale fisheries can cause declines in migratory megafauna including seabirds, marine mammals, and sea turtles, the impacts of small-scale fisheries have been largely overlooked. Small-scale fisheries occur in coastal waters worldwide, employing over 99% of the world’s 51 million fishers. New telemetry data reveal that migratory megafauna frequent coastal habitats well within the range of small-scale fisheries, potentially producing high bycatch. These fisheries occur primarily in developing nations, and their documentation and management are limited or non-existent, precluding evaluation of their impacts on non-target megafauna.

    This is a surprising and unexpected finding because you would expect smaller fishing boats to have smaller impacts. I guess smaller scale fishing fleets in Mexico (and other developing nations) have not been targeted for education, awareness and enforcement of turtle safe fishing practices.

    The good news from the study is that a major source of mortality has been identified and the authors point to recent efforts to increase awareness in the community about turtle safe fishing. But it will be a long and hard fight to be tackled all over the world.

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    Sea Turtle News o' the day – Global warming edition

    Byoliveridley

    ScienceDaily: Scientists Warn Of Climate Change Risk To Marine Turtles

    North American marine turtles are at risk if global warming occurs at predicted levels, according to scientists from the University of Exeter. An increase in temperatures of just one degree Celsius could completely eliminate the birth of male turtles from some beaches. A rise of three degrees Celsius would lead to extreme levels of infant mortality and declines in nesting beaches across the USA.

    Here’s the paper.

    Like a lot of other reptiles, the sex of the hatchling is dependent on nest temperature. Warmer temperatures make female turtles (my mnemonic was hot females!), and even warmer temperatures just kill the eggs. But, I wonder if the turtles would adapt by nesting a little earlier. I don’t think it is yet clear when turtles decide to nest. If it is based on sea temperature, then they would eventually figure it out. This paper from 2004 appears to conclude that loggerheads in Florida do nest earlier than before, so there is hope.

    John F. Weishampel, Dean A. Bagley, Llewellyn M. Ehrhart (2004) Earlier nesting by loggerhead sea turtles following sea surface warming Global Change Biology 10 (8), 1424–1427

    The onset of spring, noted by the timing of wildlife migratory and breeding behaviors, has been occurring earlier over the past few decades. Here, we examine 15 years of loggerhead sea turtle, Caretta caretta, nesting patterns along a 40.5 km beach on Florida’s Atlantic coast. This small section of beach is considered to be the most important nesting area for this threatened species in the western hemisphere. From 1989 to 2003, the annual number of nests fluctuated between 13 000 and 25 000 without a conspicuous trend; however, based on a regression analysis, the median nesting date became earlier by roughly 10 days. The Julian day of median nesting was significantly correlated with near-shore, May sea surface temperatures that warmed an average of 0.8°C over this period. This marine example from warm temperate/subtropical waters represents another response of nature to recent climate trends.

    So the truth lies somewhere between easy adaptation and giant swarms of frustrated female turtles!

  • Tuesdays with Turtles – Triumphant Return

    Byoliveridley

    So, blogging has been light this summer as Olive Ridley’s partner made her way to Canada and is settling in. Also, it is summer in BC and beautiful as hell, so the prospect of sitting down and typing on a computer with brains that are only half working, well, ain’t so hot! Also, Canada is just a much calmer place than the U.S. As I looked back at my many posts, most of them are bitter fulminations against American politics or the various shenanigans of the Emperor. Anyway, I am not under his rule any more, and while he’s gutting the Endangered Species Act as we speak, he will be history soon.

    While Canadian policy debates are equally interesting, they are generally civil in comparison, except the occasional kerfluffle where old white men want their female opponents to go back to making tea, charming…

    Anyway, I felt the blogging itch again and as always, it’s nice to get back with a story about turtles.

    Researchers say they have figured out why sea turtles that normally feed and breed in shallow water or on land will, very rarely, go deep sea diving: the reptiles are on reconnaissance.

    Sea Turtles Dive to Depths for Reconnaissance : Discovery News

    Leatherbacks have amazing diving capabilities and can get up to a kilometre below the surface. Why? for food, of course! More precisely, the promise of future food. Turns out that jellyfish (or jellyfish like animals) hang out in the deep during day time and surface at night. Leatherbacks go looking for them during the daytime down in the deeps so they can get them on the surface for dinner. It’s akin to you taking a leisurely walk around downtown looking for the perfect dinner spot.

    Interesting. As always, very fascinating and sexy creatures, and critically endangered.

    Expect more regularly scheduled blogging just in time for the late summer sweeps!

  • Tuesdays with Turtles – Poaching in Mexico

    Byoliveridley

    This article brings up some interesting information about sea turtle poaching in Mexico, including the fact that sea turtle eggs are considered aphrodisiacal in certain cultures…

    Real Men Don’t Eat Turtle Eggs : To Fight Turtle Poaching, Campaigners Hit Below the Belt (By C.J. Bahnsen)

    But there have been recent gains. WiLDCOAST, a small conservation organization also co-founded by Nichols, has implemented a media campaign. It started in 2005, when Argentine singer and Playboy model Dorismar attracted controversial attention by appearing in television and poster PSAs, hitting Mexican men—who eat turtle eggs mistakenly believing they are aphrodisiacs—below the belt. The message above a salacious Dorismar reads: “My man doesn’t need to eat turtle eggs; because he knows they don’t make him more potent.” The bold campaign reached a global audience of 300 million and resulted in a decrease in consumption of sea turtle eggs.

    Well, the unfortunate thing about aphrodisiacs is that if you believe, it works! So, I guess a Playboy model telling you that sea turtles eggs are baloney may work. They author does say there was a decrease in consumption, but presumably, it is not quite that easy to ascribe causation relationships to particular parts of a campaign!

    Other highlights…

    Turtle smuggling is thought to be a proving ground, a gateway into drug trafficking. Mexico is the principal transit country for 70 to 90 percent of cocaine entering the U.S., and the largest outside source of
    marijuana and methamphetamine.

    This, I did not know.

    Grupo Tortuguero continues its David-vs.-Goliath efforts to co-opt fishermen and volunteers from Baja’s fishing communities to monitor, tag and protect sea turtles. The group has dozens of sites along the peninsula and all have drug issues, ranging from trafficking to addiction. “I’ve interacted with fishers who were not ‘poachers,’ but were poaching for money to feed their habit,” says Nichols

    The article is interesting because it points out the similarities between sea turtle smuggling and drug smuggling, the use of young women, the co-opting of users to become dealers, the bribery of local officials, the organization to avoid capture, etc. Hmm…

  • Tuesdays with Turtles -Thursday Edition – Pacific Leatherbacks in Trouble

    Byoliveridley

    Personal Note
    I swear, this blog has gone to pot. Either I’ve been too busy at work (yes, that does not explain everything), or I have not been thinking enough. I started this blog so that when I saw something interesting, I would have to think a little bit, and gather some information to write about what I saw/read. Apparently, I don’t read/see any more (which is not true), I don’t think any more (possible), or I am too lazy to spend enough time thinking to throw a coherent blog post together.

    This has got to stop, and it stops right now!!
    End Personal Note
    Back to the topic on hand…

    The Pacific Leatherback is in serious trouble and is slated to go extinct soon.

    ENN News Network

    Experts at the Bellagio Sea Turtle Conservation Initiative have just concluded a conference to save the imperiled Pacific leatherback sea turtle from extinction. The International Union for the Conservation of Nature and Natural Resources (IUCN) has classified Pacific leatherbacks as critically endangered.

    The meeting convened an internationally diverse group of scientists, conservationists, economists, fund-raisers and policy makers. One focus was the development of immediate actions to boost hatchling production of the Western Pacific nesting populations by protecting nests from predation, beach erosion and human consumption on the beaches of Indonesia, Papua New Guinea, Solomon Islands, Vanuatu, Vietnam and Malaysia. Although there are still hundreds of turtles nesting, with 75 percent in one area on the north coast of Papua (Indonesia), researchers are concerned by new information indicating that the majority of nests laid are not producing hatchlings. Some simple procedures have been developed to improve hatch success, and applying these techniques now may ensure the populations are sustained in the future.

    Some radical measures have been suggested, including cloning. Well, highly unlikely. Jurassic Park horrors and ethical dilemmas aside, cloning reptiles ain’t so easy.

    What ails the Pacific Leatherback? Their numbers have dropped from 115000 reproductive females to less than 3000. This news release from a 2004 conference has more. But the usual suspects are destruction of nesting habitats, long line fishing, egg poaching, and to a more uncertain degree, climate change.

    It’s depressing, I’ve never seen a leatherback, I guess I need to get on the case and see one before they disappear for ever.