Featured Research

from universities, journals, and other organizations

Migrating sea turtles have magnetic sense for longitude

Date:
February 28, 2011
Source:
Cell Press
Summary:
From the very first moments of life, hatchling loggerhead sea turtles have an arduous task. They must embark on a transoceanic migration, swimming from the Florida coast eastward to the North Atlantic and then gradually migrating over the course of several years before returning again to North American shores. Now, researchers have figured out how the young turtles find their way.

A newborn caretta caretta (loggerhead) sea turtle. From the very first moments of life, hatchling loggerhead sea turtles have an arduous task. They must embark on a transoceanic migration, swimming from the Florida coast eastward to the North Atlantic and then gradually migrating over the course of several years before returning again to North American shores.
Credit: iStockphoto/Burcin Tuncer

From the very first moments of life, hatchling loggerhead sea turtles have an arduous task. They must embark on a transoceanic migration, swimming from the Florida coast eastward to the North Atlantic and then gradually migrating over the course of several years before returning again to North American shores. Now, researchers reporting online on February 24 in Current Biology have figured out how the young turtles find their way.

"One of the great mysteries of animal behavior is how migratory animals can navigate in the open ocean, where there are no visual landmarks," said Kenneth Lohmann of the University of North Carolina at Chapel Hill.

"The most difficult part of open-sea navigation is determining longitude or east-west position. It took human navigators centuries to figure out how to determine longitude on their long-distance voyages," added Nathan Putman, a graduate student in Lohmann's lab and lead author of the study. "This study shows, for the first time, how an animal does this."

It appears that the turtles pick up on magnetic signatures that vary across Earth's surface in order to determine their position in space -- both east-west and north-south -- and steer themselves in the right direction. Although several species, including sea turtles, were known to rely on magnetic cues as a surrogate for latitude, the findings come as a surprise because those signals had been considered unpromising for determining east-west position.

The loggerheads' secret is that they rely not on a single feature of the magnetic field, but on a combination of two: the angle at which the magnetic field lines intersect Earth (a parameter known as inclination) and the strength of the magnetic field.

Near the Equator, the field lines are approximately parallel to Earth's surface, Putman and Lohmann explained. As one travels north from the Equator, the field lines grow progressively steeper until they reach the poles, where they are directed straight down into Earth. The magnetic field also varies in intensity, being generally strongest near the poles and weakest near the equator. Both parameters appear to vary more reliably from north to south than east to west, which had led many researchers to conclude that the magnetic field is useful only for latitudinal information.

"Although it is true that an animal capable of detecting only inclination or only intensity would have a hard time determining longitude, loggerhead sea turtles detect both magnetic parameters," Putman said. "This means that they can extract more information from the Earth's field than is initially apparent."

What had been overlooked before is that inclination and intensity vary in slightly different directions across Earth's surface, Putman added. As a result of that difference, particular oceanic regions have distinct magnetic signatures consisting of a unique combination of inclination and intensity.

The researchers made the discovery by subjecting hatchlings to magnetic fields replicating those found at two locations, both along the migratory route but at opposite ends of the Atlantic Ocean. Each location had the same latitude but different longitude. The turtles were placed in a circular water-filled arena surrounded by a computerized coil system used to control the magnetic field and tethered to an electronic tracking unit that relayed their swimming direction.

Turtles exposed to a field like one existing on the west side of the Atlantic near Puerto Rico swam to the northeast. Those exposed to a field like that on the east side of the Atlantic near the Cape Verde Islands swam to the southwest.

The findings may have important implications for the turtles, the researchers say.

"This work not only solves a long-standing mystery of animal behavior but may also be useful in sea turtle conservation," Lohmann said. "Understanding the sensory cues that turtles rely on to guide their migrations is an important part of safeguarding their environment."

The discovery may also lead to new approaches in the development of navigational technologies, the researchers added.


Story Source:

The above story is based on materials provided by Cell Press. Note: Materials may be edited for content and length.


Journal Reference:

  1. Nathan F. Putman, Courtney S. Endres, Catherine M.F. Lohmann, Kenneth J. Lohmann. Longitude Perception and Bicoordinate Magnetic Maps in Sea Turtles. Current Biology, 24 February 2011 DOI: 10.1016/j.cub.2011.01.057

Cite This Page:

Cell Press. "Migrating sea turtles have magnetic sense for longitude." ScienceDaily. ScienceDaily, 28 February 2011. <www.sciencedaily.com/releases/2011/02/110224121855.htm>.
Cell Press. (2011, February 28). Migrating sea turtles have magnetic sense for longitude. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2011/02/110224121855.htm
Cell Press. "Migrating sea turtles have magnetic sense for longitude." ScienceDaily. www.sciencedaily.com/releases/2011/02/110224121855.htm (accessed July 25, 2014).

Share This




More Earth & Climate News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Bill Gates: Health, Agriculture Key to Africa's Development

Bill Gates: Health, Agriculture Key to Africa's Development

AFP (July 24, 2014) Health and agriculture development are key if African countries are to overcome poverty and grow, US software billionaire Bill Gates said Thursday, as he received an honourary degree in Ethiopia. Duration: 00:36 Video provided by AFP
Powered by NewsLook.com
Higgins Breaks Record at Mt. Washington

Higgins Breaks Record at Mt. Washington

Driving Sports (July 24, 2014) Subaru Rally Team USA drivers David Higgins and Travis Pastrana face off against a global contingent of racers at the annual Mt. Washington Hillclimb in New Hampshire. Includes exclusive in-car footage from Higgins' record attempt. Video provided by Driving Sports
Powered by NewsLook.com
Storm Kills Three, Injures 20 at Virginia Campground

Storm Kills Three, Injures 20 at Virginia Campground

Reuters - US Online Video (July 24, 2014) A likely tornado tears through an eastern Virginia campground, killing three and injuring at least 20. Linda So reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile: iPhone Android Web
          Follow: Facebook Twitter Google+
          Subscribe: RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins