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 firstname.lastname@example.org.
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/
Preservation of floodplains is flood protection
27.09.2017 | Technische Universität München
Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
23.10.2017 | Event News
17.10.2017 | Event News
10.10.2017 | Event News
23.10.2017 | Physics and Astronomy
23.10.2017 | Earth Sciences
23.10.2017 | Health and Medicine