DETECTION OF MAGNETIC INCLINATION ANGLE BY SEA TURTLES: A POSSIBLE MECHANISM FOR DETERMINING LATITUDE

For animals that migrate long distances, the magnetic field of the earth provides not only a possible cue for compass orientation, but a potential source of world-wide positional information. At each location on the globe, the geomagnetic field lines intersect the earth's surface at a specific angle of inclination. Because inclination angles vary with latitude, an animal able to distinguish between different field inclinations might, in principle, determine its approximate latitude. Such an ability, however, has never been demonstrated in any animal. We studied the magnetic orientation behavior of hatchling loggerhead sea turtles (Caretta caretta L.) exposed to earth-strength magnetic fields of different inclinations. Hatchlings exposed to the natural field of their natal beach swam eastward, as they normally do during their offshore migration. In contrast, those subjected to an inclination angle found on the northern boundary of the North Atlantic gyre (their presumed migratory path) swam south-southwest. Hatchlings exposed to an inclination angle found near the southern boundary of the gyre swam in a northeasterly direction, and those exposed to inclination angles they do not normally encounter, or to a field inclination found well within the northern and southern extremes of the gyre, were not significantly oriented. These results demonstrate that sea turtles can distinguish between different magnetic inclination angles and perhaps derive from them an approximation of latitude. Most sea turtles nest on coastlines that are aligned approximately northsouth, so that each region of nesting beach has a unique inclination angle associated with it. We therefore hypothesize that the ability to recognize specific inclination angles may largely explain how adult sea turtles can identify their natal beaches after years at sea.

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A Geometrical origin of the Pulsar Core and Conal Emissions

International Astronomical Union Colloquium ◽

10.1017/s0252921100041579 ◽

1996 ◽

Vol 160 ◽

pp. 229-230 ◽

Cited By ~ 1

Author(s):

R.C. Kapoor ◽

C.S. Shukre

Keyword(s):

Polar Angle ◽

Quadratic Equation ◽

Magnetic Axis ◽

Polar Cap ◽

The Core ◽

The North ◽

Polar Caps ◽

Inclination Angles ◽

Field Geometry ◽

Field Lines

We have analysed the dipole magnetic field geometry for the general case of an oblique rotator and have found that open field lines which define the polar cap divide into two branches (Kapoor and Shukre 1996) which appear naturally relevant for distinguishing the core and conal emissions. The polar cap shape is actually determined by a quadratic equation having two roots leading to two values of the polar angle,θ+andθ−with respect to the magnetic axis for a given azimuth φ. For the north pole bothθ+andθ−branches are shown as polar plots in Fig. 1 for various inclination angles α and a typical pulsar period. The discussion of pulsar polar caps hitherto (e.g. Biggs 1990) had not distinguished between theθ+and theθ−solutions. The region defined by theθ+solution is completely contained inside the polar cap. It has a peculiar triangular shape whose lowest vertex is always on the magnetic axis. This naturally suggests an identification of theθ+and theθ−regions with the core and conal emission zones.

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Multi-year tracking reveals extensive pelagic phase of juvenile loggerhead sea turtles in the North Pacific

Movement Ecology ◽

10.1186/s40462-016-0087-4 ◽

2016 ◽

Vol 4 (1) ◽

Cited By ~ 5

Author(s):

D. K. Briscoe ◽

D. M. Parker ◽

S. Bograd ◽

E. Hazen ◽

K. Scales ◽

...

Keyword(s):

North Pacific ◽

Sea Turtles ◽

Loggerhead Sea Turtles ◽

The North ◽

The North Pacific

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Orientation and open-sea navigation in sea turtles

Journal of Experimental Biology ◽

10.1242/jeb.199.1.73 ◽

1996 ◽

Vol 199 (1) ◽

pp. 73-81 ◽

Cited By ~ 4

Author(s):

K Lohmann ◽

C Lohmann

Keyword(s):

Magnetic Field ◽

Visual Cues ◽

Sea Turtles ◽

Positional Information ◽

Sea Turtle ◽

Compass Orientation ◽

Loggerhead Sea Turtle ◽

Open Sea ◽

Nesting Beaches ◽

Field Inclination

Loggerhead sea turtle hatchlings (Caretta caretta L.) emerge from underground nests, scramble to the sea and begin a transoceanic migration by swimming away from their natal beach and into the open ocean. Evidence suggests that hatchlings sequentially use three different sets of cues to maintain orientation during their initial migration offshore. While on the beach, hatchlings find the ocean by crawling towards the lower, brighter seaward horizon and away from the dark, elevated silhouettes of vegetation and dunes. Upon entering the ocean, turtles initially orient seawards by swimming into waves, which can be detected as orbital movements from under water. Laboratory experiments have demonstrated that turtles can transfer a course initiated on the basis of waves or visual cues to a course mediated by a magnetic compass. Thus, by setting a magnetic course on the basis of nearshore cues that indicate the seaward direction, hatchlings may continue on offshore headings after entering deep water beyond sight of land. Sea turtles may use the earth's magnetic field not only as a cue for compass orientation but also as a source of world-wide positional information. Recent experiments have demonstrated that loggerheads can detect subtle differences in magnetic field inclination and intensity, two geomagnetic features that vary across the surface of the earth. Because most nesting beaches and oceanic regions are marked by a unique combination of these features, these findings raise the possibility that adult sea turtles navigate using a bicoordinate magnetic map.

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Study of the change of surface magnetic field associated with flares

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311015675 ◽

2010 ◽

Vol 6 (S273) ◽

pp. 417-421

Author(s):

Yixuan Li ◽

Ju Jing ◽

Yuhong Fan ◽

Haimin Wang

Keyword(s):

Magnetic Field ◽

Inclination Angle ◽

Neutral Line ◽

Solar Physics ◽

Central Area ◽

Transverse Component ◽

Lower Altitude ◽

Surface Magnetic Field ◽

Magnetic Inclination ◽

Field Lines

AbstractHow magnetic field structure changes with eruptive events (e.g., flares and CMEs) has been a long-standing problem in solar physics. Here we present the analysis of eruption-associated changes in the magnetic inclination angle, the transverse component of magnetic field and the Lorentz force. The analysis is based on an observation of the X3.4 flare on Dec.13 2006 and a numerical simulation of a solar eruption made by Yuhong Fan. Both observation and simulation show that (1) the magnetic inclination angle in the decayed peripheral penumbra increases, while that in the central area close to flaring polarity inversion line (PIL) deceases after the flare; (2) the transverse component of magnetic field increases at the lower altitude near flaring PIL after the flare. The result suggests that the field lines at flaring neutral line turn to more horizontal near the surface, that is in agreement with the prediction of Hudson, Fisher & Welsch (2008).

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Helminth Infection of the Loggerhead Sea Turtle Caretta caretta along the Coasts of Sicily and the North West Adriatic Sea

Animals ◽

10.3390/ani11051408 ◽

2021 ◽

Vol 11 (5) ◽

pp. 1408

Author(s):

Antonino Gentile ◽

Tullia Amato ◽

Andrea Gustinelli ◽

Maria Letizia Fioravanti ◽

Delia Gambino ◽

...

Keyword(s):

Adriatic Sea ◽

Sea Turtles ◽

Single Species ◽

Caretta Caretta ◽

Sea Turtle ◽

Helminth Parasites ◽

Loggerhead Sea Turtles ◽

Loggerhead Sea Turtle ◽

North West ◽

The North

We provide new data on the presence of helminth parasites in 64 individual loggerhead sea turtles Caretta caretta stranded along the coasts of Sicily and the northwest Adriatic Sea between June 2014 and August 2016. The necropsy examination revealed 31 individuals (48.4%) positive for endoparasites, showing a greater prevalence of trematodes than nematodes. In particular, seven species and a single genus of Trematoda (Hapalotrema) and a single species and genus of Nematoda (Kathlania) were identified. Among the Digenea flukes the species with the highest prevalence of infection were Rhytidodes gelatinosus (34.6%) and Hapalotrema sp. (33.3%), while among the Nematoda they were Kathlania sp. (33.3%) and Sulcascaris sulcata (33.3%). Analysis of variance (ANOVA) was applied among the recovery sites of the stranded loggerhead sea turtles and prevalence of endoparasites was used to highlight any relationship between the parasites and the origin of the hosts. ANOVA showed significant differences (p < 0.001) among the data used.

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Dynamic Thermal Corridor May Connect Endangered Loggerhead Sea Turtles Across the Pacific Ocean

Frontiers in Marine Science ◽

10.3389/fmars.2021.630590 ◽

2021 ◽

Vol 8 ◽

Author(s):

Dana K. Briscoe ◽

Calandra N. Turner Tomaszewicz ◽

Jeffrey A. Seminoff ◽

Denise M. Parker ◽

George H. Balazs ◽

...

Keyword(s):

North Pacific ◽

Bone Growth ◽

Sea Turtles ◽

Sea Turtle ◽

Loggerhead Sea Turtles ◽

Data Set ◽

Loggerhead Sea Turtle ◽

The North ◽

Ocean Conditions ◽

Formed Part

The North Pacific Loggerhead sea turtle (Caretta caretta) undergoes one of the greatest of all animal migrations, nesting exclusively in Japan and re-emerging several years later along important foraging grounds in the eastern North Pacific. Yet the mechanisms that connect these disparate habitats during what is known as the “lost years” have remained poorly understood. Here, we develop a new hypothesis regarding a possible physical mechanism for habitat connectivity – an intermittent “thermal corridor” – using remotely sensed oceanography and 6 juvenile loggerhead sea turtles that formed part of a 15 year tracking dataset of 231 individuals (1997–2013). While 97% of individuals remained in the Central North Pacific, these 6 turtles (about 3%), continued an eastward trajectory during periods associated with anomalously warm ocean conditions. These few individuals provided a unique opportunity to examine previously unknown recruitment pathways. To support this hypothesis, we employed an independently derived data set using novel stable isotope analyses of bone growth layers and assessed annual recruitment over the same time period (n = 33, 1997–2012). We suggest evidence of a thermal corridor that may allow for pulsed recruitment of loggerheads to the North American coast as a function of ocean conditions. Our findings offer, for the first time, the opportunity to explore the development of a dynamic ocean corridor for this protected species, illuminating a longstanding mystery in sea turtle ecology.

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Record of the Loggerhead Sea Turtle, Caretta caretta (Testudines, Cheloniidae), in the Black Sea with the Review of the Species Occurrence in the Region

Zoodiversity ◽

10.15407/zoo2021.02.127 ◽

2021 ◽

Vol 55 (2) ◽

pp. 127-132

Author(s):

O. Zinenko ◽

K. A. Vishnyakova ◽

L. Stoyanov ◽

P. E. Gol’din

Keyword(s):

Black Sea ◽

Sea Turtles ◽

Caretta Caretta ◽

First Record ◽

Sea Turtle ◽

The Black Sea ◽

Loggerhead Sea Turtles ◽

Loggerhead Sea Turtle ◽

The North ◽

North Western

A rare live record of the loggerhead sea turtle Caretta caretta (Linnaeus, 1758) is reported from the Dzharylgach Gulf in the north-western Black Sea. This is the first record from Ukrainian waters since 1962 and the northernmost record of the species in the Black Sea. The loggerhead sea turtles of the east Mediterranean origin are increasingly often seen in the Marmara and the Black Sea during the latest decade, which is an evidence for potential expansion of this species range, at least partly due to climate changes. Key words: sea turtles, Caretta caretta, Black Sea, Ukraine, range expansion.

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Identification of likely foraging habitat of pelagic loggerhead sea turtles (Caretta caretta) in the North Atlantic through analysis of telemetry track sinuosity

Progress In Oceanography ◽

10.1016/j.pocean.2010.04.009 ◽

2010 ◽

Vol 86 (1-2) ◽

pp. 224-231 ◽

Cited By ~ 29

Author(s):

Abigail L. McCarthy ◽

Selina Heppell ◽

Francois Royer ◽

Carla Freitas ◽

Thomas Dellinger

Keyword(s):

North Atlantic ◽

Sea Turtles ◽

Caretta Caretta ◽

Foraging Habitat ◽

Loggerhead Sea Turtles ◽

The North ◽

The North Atlantic

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Estimating the age of juvenile loggerhead sea turtles in the North Atlantic

Canadian Journal of Zoology ◽

10.1139/z97-005 ◽

1997 ◽

Vol 75 (1) ◽

pp. 40-46 ◽

Cited By ~ 58

Author(s):

G. C. Hays ◽

R. Marsh

Keyword(s):

North Atlantic ◽

Sea Turtles ◽

Drift Time ◽

Loggerhead Sea Turtles ◽

The North ◽

The United Kingdom ◽

The North Atlantic ◽

Area North ◽

Using Data ◽

Nesting Beaches

Analysis of previously published records shows that the modal size of juvenile loggerhead sea turtles (Caretta caretta) found around the United Kingdom (the area north of 49°N and east of 12°W) is a carapace length of 20.5 cm. These turtles are believed to originate from nesting beaches in North America (principally Florida). We estimated their trans-Atlantic drift time using data from satellite-tracked buoys and from a mathematical model and, hence, estimated that the modal age of these juvenile turtles was between 1.80 and 3.75 years.

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