Navigation Links
No place like home: New theory for how salmon, sea turtles find their birthplace
Date:12/1/2008

CHAPEL HILL 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."


'/>"/>

Contact: Patric Lane
patric_lane@unc.edu
919-962-8596
University of North Carolina at Chapel Hill
Source:Eurekalert

Related biology news :

1. Emphasis on conifer forests places multiple species at risk
2. Opportunity for students displaced by Katrina to assess climate vulnerability of Southeast US
3. IEEE-USA innovation forum will help prepare US tech leaders to prosper in a global marketplace
4. In-vitro fertilization improved with 3-D/4-D-guided embryo transfer and new placement target
5. Single-largest biodiversity survey says primary rainforest is irreplaceable
6. Katherine Freed wins first place at the International ISPE Undergraduate Poster Contest
7. Listen-up ladies: Dont postpone knee-replacement surgery
8. MU researcher links hormone replacement therapy to breast cancer
9. A place in the sun
10. Testosterone replacement theraphy beneficial in men 60 and older
11. Clues to ancestral origin of placenta emerge in Stanford study
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/15/2016)... 15, 2016 --> ... Transparency Market Research "Digital Door Lock Systems Market - Global ... 2023," the global digital door lock systems market in terms ... and is forecast to grow at a CAGR of 31.8% ... and medium enterprises (MSMEs) across the world and high industrial ...
(Date:3/11/2016)... --> --> ... Recognition Market by Technology (Pattern Recognition), by Component (Hardware, ... Type (On-Premises and Cloud), by Industry Vertical and by ... the global market is expected to grow from USD ... 2020, at a CAGR of 19.1%. , ...
(Date:3/9/2016)... 9, 2016  Crossmatch ® , a leading ... today announced the addition of smart features to ... multi-factor authentication platform. New contextual and application-specific authentication ... security where it,s needed most — while minimizing ... . --> Washington, DC ...
Breaking Biology News(10 mins):
(Date:5/25/2016)... ... May 25, 2016 , ... Founder of ... board-certified in surgery and surgery of the hand by the National Board of ... to going above and beyond in his pursuit of providing the most comprehensive, ...
(Date:5/25/2016)... ... May 25, 2016 , ... Lady had been battling arthritis since ... ligament in her left knee. Lady’s owner Hannah sought the help of Dr Jeff ... surgeon, to repair her cruciate ligament and help with the pain of Lady’s arthritis. ...
(Date:5/24/2016)... ... May 24, 2016 , ... Last week, Callan Capital, ... executives and entrepreneurs, held The Future of San Diego Life Science event at the ... life science community attended the event with speakers Dr. Rich Heyman, former CEO of ...
(Date:5/23/2016)... May 23, 2016 Zimmer Biomet Holdings, Inc. (NYSE ... announced that its Board of Directors has approved the payment ... quarter of 2016. The cash dividend of ... 29, 2016 to stockholders of record as of the close ... are subject to approval of the Board of Directors and ...
Breaking Biology Technology: