By Giovanni Casotti Department of Biology West Chester University, West Chester, PA Lost? Ask a Turtle: Navigation and Migration in Loggerheads.

by

Giovanni Casotti

Department of Biology

West Chester University, West Chester, PA

Lost? Ask a Turtle:

Navigation and Migration in Loggerheads

Terminology

NavigationoMoving along a course

MigrationoMoving from one region to another

HomingoReturning back to a specific point

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MigrationReproductive success

– Sockeye salmon (lifecycle migration and homing)

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MigrationReproductive success

– Loggerhead turtles

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− Elephant seals

Case Case Study

Loggerhead turtles1.How do hatchlings navigate to the ocean? What dangers are faced by newly emerging turtles hatchlings?

2.Once in the water, what mechanism do hatchling turtles use to make their way toward open ocean?

3.Once off the coast, juveniles make their way to the North Atlantic Current (Gyre). Describe this pathway.

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Migration

Food acquisition– Humpback whales

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Navigation Strategies

Trail following– Employed by

invertebrates only (ants)

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Piloting‒Using landmarks to navigate (pigeons)

Navigation Strategies

Path integration– Employed by invertebrates only (ants)

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Return journey

Navigation Strategies

Map and compass navigation– Used by long distance migrators (whales and turtles)

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Terrestrial AnimalsCompass navigation

– Using Earth’s magnetic field

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Case Study

Watch the video on turtle navigation:http://www.youtube.com/watch?v=LbiBXRtiVrg

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Magnetite Receptors

Located in beaks of birds

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Magnetite Receptors2 possible mechanisms of action

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Case Study

Question4.How do hatchling and adult turtles find their way along their migratory pathway? What methods did scientists use to identify the mechanism responsible for long distance navigation in sea turtles?

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Navigation Strategies

Compass navigation– Using the sun (starlings)

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Sunlight

Sunlight

Navigation Strategies

Compass navigation– Using the stars (Indigo buntings)

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Navigation Strategies

Olfactory cues: Detection of dimethyl sulphide (DMS)

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Case StudyQuestions5.Birds might use DMS to navigate. What produces DMS and what methods did researchers use to determine this? In what oceans has DMS been measured?

6.What about seals? Why do the researchers think that seals use visual cues to navigate?

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Case StudyQuestions7.Why did the researchers discount the possibility of geomagnetic, celestial, acoustic and olfactory cues as navigational tools in seals?

8.Migrating in the open ocean can be more challenging than a land migration. Describe these differences.

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Image CreditsSlide 1Photo ©Nexus7 | Dreamstime.com, ID#28139654, licensed for use.

Slide 2Photo by Hila Shaked, “Hatchling Loggerhead sea turtles near Atlit, Israel, on their way to the ocean,” http://commons.wikimedia.org/wiki/File:Hatchling_Loggerhead_Sea_Turtles_near_Atlit_Israel.jpg), CC BY-SA 3.0.

Slide 3 (left)Photo of spawning sockeye salmon by Theinterior, http://commons.wikimedia.org/wiki/File:SockeyeSpawn_inAdams.JPG, CC BY 3.0.

Slide 3 (right)Figure 5 from: Lohmann, K. J., Lohmann, C.M.F. , and Endres, C.S. 2008. The sensory ecology of ocean navigation. J Exp Biol June 2008 vol. 211 no. 11 1719-1728. http://jeb.biologists.org/content/211/11/1719/F5.expansion.html#ref-19.

Slide 4 (left)Crop of Fig 3 in:Lohmann, K. J., Lohmann, C. M. F. and Endres, C. S. 2008. The sensory ecology of ocean navigation. J. Exp. Biol. 211: 1719–1728. Available online at http://jeb.biologists.org/content/211/11/1719.long. Last accessed March 27, 2014. CC-BY 3.0.

Slide 4 (right)Distribution of the northern elephant seal (dark blue: breeding colonies; light blue: non-breeding individuals) , by Mirko Thiessen, http://en.wikipedia.org/wiki/File:Mirounga_angustirostris_distribution.png, CC BY-SA 3.0.

Slide 6National Park Service, US Department of the Interior. Humpback Whale (Megaptera novaeangliae).http://www.nature.nps.gov/biology/migratoryspecies/humpbackwhale.cfm.

Slide 7 (left)Photo of ant trail by Wikipedia User:Fir0002, http://commons.wikimedia.org/wiki/File:Ant_trail.jpg, CC BY-SA 3.0.

Slide 7 (right)Julius Neubronner's tiny cameras strapped to homing pigeons, http://commons.wikimedia.org/wiki/File:Pigeoncameras.jpg, public domain. 20

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Slide 8Created by author.

Slide 9NASA, http://www.nasa.gov/images/content/607968main_geomagnetic-field-orig_full.jpg.

Slide 10Schematic of experimental setup and photo of turtle in harness provided by The Lohman Lab, Department of Biology, University of North Carolina, Chapel Hill, NC (http://www.unc.edu/depts/geomag/), used with permission.

Slide 12Figure 7 in:Pósafi, M., and R. E. Dunin-Borkowski. 2009. Magnetic nanocrystals in organisms. Elements 5: 235-240. Used with the permission of the Mineralogical Society of America.

Slide 13Panels B and C of Figure 4 in:Pósafi, M., and R. E. Dunin-Borkowski. 2009. Magnetic nanocrystals in organisms. Elements 5: 235-240. Used with the permission of the Mineralogical Society of America.

Slide 15Adapted from Fig. 27.21, page 603 In: Hickman CP, Roberts, L.S. Keen, SL, Larson, A., I’Anson, H and Eisenhour, D.J. (2008). Integrated Principles of Zoology. 14th ed. McGraw-Hill, Boston. ISBN 978-0-07-722126-3.

Slide 16Modified from: Emlen, ST (1967). Migration orientation in the Indigo Bunting, Passerina cyanea: Part 1 Evidence for the use of celestial cues. The Auk, 84: (3) 309-342. https://sora.unm.edu/sites/default/files/journals/auk/v084n03/p0309-p0342.pdf

Slide 17 Figure 1 in: Nevitt, G. A. and Bonadonna, F. 2005. Sensitivity to dimethyl sulphide suggests a mechanism for olfactory navigation by seabirds. 1: 303305. Available online at http://rsbl.royalsocietypublishing.org/content/1/3/303.full. Used with permission.