Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

No Place Like Home: New Theory for How Salmon, Sea Turtles Find Their Birthplace

03.12.2008
How marine animals find their way back to their birthplace to reproduce after migrating across thousands of miles of open ocean has mystified scientists for more than a century. But marine biologists at the University of North Carolina at Chapel Hill think they might finally have unraveled the secret.

At the beginning of their lives, salmon and sea turtles may read the magnetic field of their home area and “imprint” on it, according to a new theory in the latest issue of the journal Proceedings of the National Academy of Sciences.

The Earth’s magnetic field varies predictably across the globe, with every oceanic region having a slightly different magnetic signature. By noting the unique “magnetic address” of their birthplace and remembering it, animals may be able to distinguish this location from all others when they are fully grown and ready to return years later, researchers propose.

Previous studies have shown that young salmon and sea turtles can detect the Earth’s magnetic field and use it to sense direction during their first migration away from their birthplace to the far-flung regions where they spend the initial years of their lives.

The new study seeks to explain the more difficult navigational task accomplished by adult animals that return to reproduce in the same area where they themselves began life, a process scientists refer to as natal homing.

“What we are proposing is that natal homing can be explained in terms of animals learning the unique magnetic signature of their home area early in life and then retaining that information,” said Kenneth Lohmann, Ph.D., professor of biology in the UNC College of Arts and Sciences and the first author of the study. “We hope that the paper will inspire discussion among scientists and eventually lead to a way of testing the idea.”

The theory builds on previous studies with sea turtles by Lohmann and his team. In 2001, they showed that baby turtles use magnetic information to help guide them during their first migration across the Atlantic Ocean. And in 2004 they discovered that sea turtles several years of age possess a more sophisticated “magnetic map” sense that helps them navigate to specific areas rich in food.

Sea turtles and salmon are among nature’s most impressive ocean travelers but, no matter how long or far they journey, both seem to remember where home is. Some populations of sea turtles, for example, cross entire oceans and are absent from their home beach for more than a decade before returning to reproduce. Salmon hatch in rivers, then migrate hundreds of miles out into the ocean before returning to their home river several years later to spawn.

Just why marine animals migrate such vast distances to return to their own birthplace, sometimes bypassing other suitable locations along the way, is not known. Scientists speculate that natal homing evolved because individuals that returned to their home areas to reproduce left more offspring than those that tried to reproduce elsewhere.

“For animals that require highly specific environmental conditions to reproduce, assessing the suitability of an unfamiliar area can be difficult and risky,” Lohmann said. “In effect, these animals seem to have hit on a strategy that if a natal site was good enough for them, then it will be good enough for their offspring.”

The study notes that the Earth’s magnetic field changes slightly over time and thus probably only helps animals arrive in the general region of their birthplace. Once an animal is close to the target, other senses, such as vision or smell, may be used to pinpoint specific reproductive sites. Salmon, for example, are known to use smell to locate spawning grounds once they have drawn near.

Lohmann said one problem making it difficult to test the new theory is the low survival rate of sea turtles. Only one out of about 4,000 baby sea turtles survives to adulthood and returns to its natal site to breed. A similarly small percentage of baby fish survive.

Lohmann also notes that if the theory is correct, it could lead to new ways of helping save sea turtles and salmon. “Ideally, it might be possible to steer turtles to protected areas where we would like them to nest,” Lohmann said, noting the animals’ endangered status. “It might also be possible to use magnetic imprinting to help re-establish salmon populations in rivers where the original population has been wiped out.”

Along with Lohmann, UNC researchers Catherine Lohmann, Ph.D., lecturer of biology, and Nathan Putman, a graduate student in the department, co-authored the paper. The study was funded by the National Science Foundation.

Note: Lohmann can be reached at (919) 962-1332 or klohmann@email.unc.edu.

To see associated pictures, go to: http://uncnews.unc.edu/embargoed/science-and-technology/sea-turtles.html

Lohmann’s Web site: http://www.unc.edu/depts/geomag/

Dee Reid | Newswise Science News
Further information:
http://www.unc.edu
http://www.unc.edu/depts/geomag/

Further reports about: Birthplace SEA UNC magnetic field magnetic map marine animals sea turtles turtles

More articles from Ecology, The Environment and Conservation:

nachricht Dune ecosystem modelling
26.06.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht Understanding animal social networks can aid wildlife conservation
23.06.2017 | Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB)

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Study shines light on brain cells that coordinate movement

26.06.2017 | Life Sciences

Smooth propagation of spin waves using gold

26.06.2017 | Physics and Astronomy

Switchable DNA mini-machines store information

26.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>