The Cartography of the Deep: Unlocking the Mechanics of the Sea Turtle’s Magnetic Map

Abstract

The navigational capabilities of the loggerhead sea turtle (Caretta caretta) have long represented one of the most profound enigmas in sensory biology and movement ecology. Emerging from subterranean nests on the sandy littorals of the southeastern United States, these reptilian mariners embark on a transoceanic odyssey—a multi-year migration spanning the North Atlantic Gyre—before returning with high fidelity to their natal regions. While the mid-20th century established the role of the Earth's magnetic field as a primary navigational cue for these and other long-distance migrants, the biophysical transduction mechanisms underpinning this "sixth sense" have remained a subject of contentious debate. A dichotomy has persisted in the literature: does the animal "see" the magnetic field via quantum mechanical effects modulated by light-sensitive proteins in the retina, or does it "feel" the field through the mechanical torque of biogenic magnetite crystals embedded in somatic tissue?

This comprehensive research report analyzes the seminal 2025 study by Mackiewicz, Lohmann, and colleagues, published in the Journal of Experimental Biology, which provides definitive behavioral evidence resolving this duality. By employing a novel food-anticipatory assay—the "turtle dance"—and subjecting hatchlings to high-intensity magnetic pulses designed to alter the polarity of biogenic magnetite, the researchers have demonstrated that the loggerhead's magnetic map sense is derived from a magnetite-based receptor system. This finding supports a "Two-Sense" hypothesis: a light-dependent radical pair mechanism likely functioning as a compass, and a magnetite-based receptor functioning as a geographic map. This report synthesizes the historical trajectory of magnetoreception research, the quantum and classical physics of the proposed mechanisms, the innovative methodology of the recent breakthrough, and the profound implications for evolutionary biology and marine conservation in an era of increasing anthropogenic electromagnetic noise.

1. Introduction: The Navigator’s Paradox and the Blue Desert

The open ocean is a sensory desert. To the human observer, the pelagic zone of the North Atlantic offers no landmarks; there are no mountains to triangulate, no rivers to follow, and the changing celestial canopy provides only temporal and cardinal guidance, not positional fixation. Yet, for the loggerhead sea turtle (Caretta caretta), this featureless expanse is a highway, a complex grid of coordinates that must be navigated with life-or-death precision. From the moment a hatchling erupts from the sand of a Florida beach, it is engaged in a desperate race against predation, dehydration, and oceanographic dynamics.¹ This frantic scramble toward the surf initiates a migration that spans entire ocean basins and lasts for years—a period historically referred to by biologists as the "Lost Years" because the turtles seemingly vanished into the deep ocean, only to reappear as juveniles in coastal foraging grounds years later.²

We now understand that these years are not spent aimlessly drifting. Survival in the North Atlantic Gyre requires active, sophisticated navigation. A turtle that drifts passively risks being swept north into the lethal, chilling waters of the North Atlantic current or washed back to shore before it has grown large enough to survive nearshore predators. To survive, the turtle must possess a cognitive map of its world. It must know not only which way is north (orientation) but also where it is located relative to the safe, warm currents of the gyre (navigation). This requires two distinct sensory tools: a compass to maintain a heading, and a map to determine global position.¹

1.1 The Theoretical Framework: Map versus Compass

The distinction between map and compass is fundamental to the study of animal navigation, a concept first formalized by Gustav Kramer in the 1950s regarding avian migration. It is a distinction that separates simple orientation from true navigation.

• The Compass Sense: This provides directional information—North, South, East, West. It allows an animal to maintain a straight line of travel. However, a compass alone is insufficient for homing or correcting for displacement. If a turtle is blown 500 miles east by a storm, a compass will tell it which way is north, but it will not tell it that it is now east of its target and needs to adjust its course.⁴

• The Map Sense: This provides positional information—latitude and longitude. It tells the animal its location on the planet's surface relative to a goal. It answers the question, "Where am I?" rather than "Which way am I facing?".⁴

By the early 21st century, it was well-established that loggerhead turtles possess both capabilities. The laboratory of Kenneth and Catherine Lohmann at the University of North Carolina at Chapel Hill—the epicenter of sea turtle navigation research—had previously demonstrated that hatchlings can detect magnetic inclination (the angle at which magnetic field lines intersect the Earth's surface) and magnetic intensity (the strength of the field).⁶ Because these two variables vary across the globe in a predictable grid-like pattern, a turtle can theoretically determine its global position by sensing the unique magnetic "signature" of a geographic location.⁵

1.2 The Biophysical Black Box

While the existence of the magnetic sense was proven through behavioral experiments, the mechanism remained elusive. Unlike vision, which has a clear organ (the eye) and a well-understood transducer (photoreceptors converting photons to electrical signals), the magnetic sense has no obvious external organ. The magnetic field passes through biological tissue unimpeded, meaning the sensor could theoretically be located anywhere inside the animal's body. This biophysical ambiguity led to two competing hypotheses regarding the physical transduction of the magnetic field, often summarized as the "See" versus "Feel" debate:

1. The Radical Pair Mechanism (The "See" Hypothesis): Proposed to occur in the eye, involving light-sensitive proteins called cryptochromes. This mechanism relies on quantum coherence and electron spin states, theoretically allowing an animal to perceive magnetic field lines as a visual pattern overlaid on their normal vision.⁹

2. The Magnetite Hypothesis (The "Feel" Hypothesis): Proposed to involve intracellular crystals of magnetite ($Fe_3O_4$), a permanently magnetic iron mineral. These crystals would physically rotate or torque in response to the Earth's field, triggering mechanoreceptors in the cytoskeleton.¹

The breakthrough of the Mackiewicz et al. (2025) study lies in experimentally disentangling these two mechanisms. By subjecting turtles to high-intensity magnetic pulses known to affect the physical magnetization of magnetite but not the quantum states of radical pairs, the researchers successfully isolated the physical basis of the map sense, providing the first direct evidence that while turtles may see their compass, they feel their map.¹¹

2. The Subject: Caretta caretta and the Atlantic Odyssey

To understand the necessity of such a sophisticated navigation system, one must appreciate the life history of the loggerhead sea turtle. The sensory biology of an organism is shaped by its ecology; the loggerhead's magnetic map is an evolutionary response to the vast, featureless, and dynamic environment of the open ocean.

2.1 The Cycle of Migration

The life of a loggerhead begins in a buried clutch of eggs on the beaches of the southeastern United States, primarily Florida. Upon hatching, usually at night, the neonates exhibit a frenzy of activity known as the "seafinding" phase. They locate the ocean using visual cues, moving away from dark silhouettes (dunes) and toward the brighter horizon over the ocean.¹³ Once in the water, they swim into the waves (wave orientation) to move offshore.

However, once they reach the open ocean, visual cues vanish. The seabed is miles below, and the horizon is equidistant in all directions. It is here, entering the Florida Current and the Gulf Stream, that the magnetic sense becomes paramount. These currents form the western boundary of the North Atlantic Subtropical Gyre, a massive circular system of currents that rotates clockwise around the Sargasso Sea.

The "Lost Years" are spent riding these currents. For a period ranging from 7 to 12 years, the turtles circle the Atlantic, passing the Azores, drifting south toward the Canary Islands and Cape Verde, and eventually crossing back west toward the Americas.¹ This is not a passive drift. The gyre is bounded by lethal thermal barriers. To the north lies the distinct temperature drop of the sub-polar waters. A cold-stunned turtle is a dead turtle. To the south, currents can sweep unwary drifters into the South Atlantic, removing them from their population's breeding pool. The turtle must constantly assess its latitude and longitude to adjust its swimming and stay within the "Goldilocks zone" of the gyre.²

2.2 The Necessity of a Map

The precision required for this retention in the gyre implies a map. A simple compass would allow a turtle to swim East, but it would not tell the turtle when to stop swimming East and start swimming South to catch the Canary Current. The Lohmann Lab's previous work demonstrated that hatchlings collected from Florida and exposed to magnetic fields replicating those found near Portugal (the eastern side of the Atlantic) oriented South—a heading that would keep them in the gyre. Conversely, hatchlings exposed to fields replicating the northern boundary of the gyre swam South-Southwest, avoiding the cold water.⁷

This context establishes the biological stakes. The magnetic map is not a luxury; it is a survival necessity. The recent study by Mackiewicz et al. (2025) moves beyond asking if they use a map, to asking how the physics of that map operates.

3. The Geophysical Stage: Earth’s Magnetic Field

The "map" that the turtles are reading is generated by the geophysics of the planet itself. The Earth behaves as a giant dipole magnet, with field lines emerging from the Southern Hemisphere and re-entering in the Northern Hemisphere. This field is generated by the geodynamo—the turbulent convection of molten iron alloys in the Earth's outer core.

3.1 The Elements of the Magnetic Map

For a navigator, the geomagnetic field offers a predictable landscape defined by several vector components. The reliability of the magnetic map depends on the stability and gradients of these components.

• Magnetic Intensity (Field Strength): The magnitude of the magnetic force. It is generally strongest at the magnetic poles (approx. 60,000 nT or 60 microTesla) and weakest at the magnetic equator (approx. 30,000 nT). In the North Atlantic, isodynamics (lines of equal intensity) run roughly Northeast-Southwest.⁵

• Magnetic Inclination (Dip Angle): The angle at which the magnetic field lines intersect the Earth's surface. At the magnetic equator, the lines are parallel to the ground (0° inclination). At the magnetic poles, they are perpendicular (90°). In the North Atlantic, isoclinics (lines of equal inclination) run roughly East-West.¹⁵

• Declination: The angle between magnetic North and true geographic North. While useful for human navigators adjusting compasses, its utility for animals is debated, though some birds may detect it.

3.2 The Bicoordinate Grid

The intersection of isodynamics (intensity) and isoclinics (inclination) creates a bi-coordinate grid across the ocean. While not a perfect Cartesian grid (the lines are not always perpendicular), they diverge enough to provide unique "magnetic addresses" for geographic locations.¹⁵

For example, a location off the coast of Florida might have an inclination of 58° and an intensity of 48,000 nT. A location near the Azores might have an inclination of 60° but an intensity of 44,000 nT. If a turtle can sense both parameters, it can triangulate its position. The Lohmanns' research has confirmed that Caretta caretta is sensitive to both parameters independently.⁵ The Mackiewicz study focuses on the transduction of these parameters—how the physical field is converted into a neural signal.

4. The Biophysics of Magnetoreception: Two Roads to Detection

The central question addressed by the 2025 study is the physical mechanism of detection. Theoretical biophysics posits two primary candidates for magnetoreception in terrestrial animals. These mechanisms operate on fundamentally different physical principles, which allows them to be distinguished experimentally.

4.1 The Radical Pair Mechanism (The "See" Hypothesis)

This hypothesis suggests that magnetoreception is a photochemical process rooted in quantum biology.

• The Molecule: The primary candidate is cryptochrome, a flavoprotein found in the retinas of birds and turtles. Cryptochromes are sensitive to blue light.¹⁰

• The Mechanism: When a photon of blue light hits a cryptochrome molecule, it triggers the transfer of an electron, creating a "radical pair"—two molecules with unpaired electrons. The spins of these electrons can be either aligned (triplet state) or antiparallel (singlet state).

• The Magnetic Effect: The Earth's weak magnetic field can influence the rate at which the radical pair shifts between singlet and triplet states. This ratio of states affects the chemical yield of the protein, which modulates the visual signal sent to the brain.

• The Result: The animal theoretically perceives the magnetic field as a modulation of light intensity or color—essentially "seeing" the magnetic compass heading.⁹

• Key Characteristic: Because this relies on transient electron spin states, it is insensitive to brief, strong magnetic pulses. A pulse might momentarily affect a radical pair, but once the pulse ends, the chemical system resets immediately.¹⁸

4.2 The Magnetite Mechanism (The "Feel" Hypothesis)

This hypothesis relies on classical electromagnetism and the properties of ferrimagnetic minerals.

• The Mineral: Magnetite ($Fe_3O_4$) is a naturally occurring iron oxide that is permanently magnetic at physiological temperatures. It has been found in bacteria, chitons, fish noses, and bird beaks.²⁰

• The Mechanism: Single-domain crystals of magnetite act like microscopic compass needles. When embedded in a cellular membrane or coupled to the cytoskeleton of a neuron, the Earth's magnetic field exerts a torque on the crystal, attempting to align it with the field lines.

• Transduction: This mechanical torque opens ion channels (likely piezoelectric or mechanosensitive channels), causing the neuron to fire. This is a tactile sense—a "feeling" of the magnetic pull.¹

• Key Characteristic: Because magnetite crystals are permanent magnets, they are highly sensitive to strong magnetic pulses. A strong magnetic pulse (stronger than the coercivity of the crystal) can remagnetize the crystal, reversing its polarity, or physically disrupt chains of crystals.³

4.3 The Diagnostic: The Magnetic Pulse

The different susceptibilities of these two mechanisms to high-intensity magnetic pulses provide the experimental "litmus test" used by Mackiewicz et al.

• The Pulse: A typical pulse used in these experiments is approximately 0.1 Tesla (100 mT). This is about 2,000 times stronger than the Earth's field (0.05 mT).

• The Logic: If the navigation behavior is based on the Radical Pair Mechanism (Cryptochrome), the pulse should have no lasting effect, as the electron spins reset instantly. If the behavior is based on Magnetite, the pulse should disrupt the behavior for hours or days, as the physical crystals have been remagnetized or disordered.¹²

This diagnostic tool has been the gold standard in magnetoreception physics, previously used to suggest magnetite use in bats and mole rats. The 2025 study applied it to the map sense of turtles for the first time.³

5. The 2025 Study: Methodology and the "Turtle Dance"

The study titled "Disruption of the sea turtle magnetic map sense by a magnetic pulse," published in November 2025 by Alayna Mackiewicz, Catherine Lohmann, Kenneth Lohmann, and colleagues, represents a methodological triumph in behavioral ecology.¹ Solving the riddle of the map sense required not just biophysics, but a breakthrough in behavioral conditioning.

5.1 The Challenge of Testing "Location"

Traditionally, orientation studies involved placing a turtle in a tank and observing which direction it swam. However, distinguishing a "map" response from a "compass" response in a swim tank is difficult. The researchers needed a behavior that signaled recognition of a place, independent of directional swimming. They needed the turtle to say, "I know where I am."

5.2 The Innovation: Food-Anticipatory Activity (The "Turtle Dance")

The breakthrough came from co-author Kayla Goforth, who developed a Pavlovian conditioning assay. The team discovered that hatchling loggerheads could be trained to associate specific magnetic field parameters with a food reward.¹

• Conditioning: Hatchlings were placed in a coil system that generated the magnetic signature of a specific location (e.g., the fields found near Haiti or Turks and Caicos). While in this field, they were fed.

• The Behavior: The turtles developed a food-anticipatory activity (FAA) specific to that magnetic field. This behavior, dubbed the "turtle dance," is distinct and quantifiable. It involves the turtle tilting its body vertically (head up, tail down), raising its head near or above the water surface, opening its mouth, and rapidly paddling or waggling its front flippers, often spinning in circles.¹

• Significance: This behavior is an unambiguous sign of recognition. If the turtle performs the dance in the magnetic field before food is presented, it confirms the turtle has identified the magnetic signature of the "reward zone."

5.3 Experimental Design: The Pulse Protocol

The experiment followed a rigorous "train, disrupt, test" protocol designed to isolate the mechanism of this recognition.³

Phase 1: Training

Hatchlings were conditioned to associate a specific magnetic field (Field A) with food. A second field (Field B) was presented without food to serve as a control, ensuring the turtles were responding to the specific magnetic parameters and not just the presence of any magnetic field. The turtles successfully learned to dance in Field A.1

Phase 2: The Treatment

Once conditioned, the turtles were divided into three groups to test the effect of a magnetic pulse.

1. No Pulse (Control): Turtles were handled and moved but not subjected to the pulse machine. This established the baseline behavior.

2. Sham Pulse (Control): Turtles were placed inside the pulse magnetizer, but the capacitor bank was discharged in a way that produced the noise and vibration of the machine without generating the magnetic field. This was a critical control to rule out stress, handling, or acoustic noise as the cause of any behavioral change.³

3. Pulse (Experimental): Turtles were placed in the magnetizer and subjected to a brief (5 ms), high-intensity (~85 mT) magnetic pulse. This field strength is sufficient to remagnetize single-domain magnetite.³

Phase 3: The Test

Following the treatment, all turtles were returned to Field A (the food-associated field). The researchers then quantified the intensity and duration of the "turtle dance" behavior.

6. Results and Synthesis: The Magnetite Map

The results of the Mackiewicz et al. study were statistically robust and theoretically decisive.

6.1 The Silence on the Dance Floor

• Control Groups: Turtles in both the "No Pulse" and "Sham Pulse" groups exhibited high levels of the "turtle dance" when placed in the rewarded magnetic field. They correctly identified their location and anticipated food. The fact that the Sham group performed normally proved that the stress of handling and the noise of the machine did not disrupt their memory or behavior.¹¹

• Pulse Group: The turtles that received the magnetic pulse showed a significant reduction in dancing behavior. Despite being in the "food" field, they failed to recognize it. Their map sense had been temporarily blinded—or more accurately, "numbed".¹

6.2 Data Interpretation: The "Two-Sense" Hypothesis

The suppression of the map behavior by a magnetic pulse provides the "smoking gun" for the involvement of magnetite. Since the pulse does not affect cryptochrome (the chemical compass), the disruption of the map sense implies that the map and the compass rely on different physical mechanisms.

This finding supports the Two-Sense Hypothesis, proposing a sophisticated division of labor in the sea turtle's sensory suite:

Sensory Function	Likely Mechanism	Physical Basis	Pulse Sensitivity	Function
The Compass	Cryptochrome (Radical Pair)	Quantum Spin Chemistry (Vision)	No	Determines Direction (North/South)
The Map	Magnetite	Classical Ferromagnetism (Touch)	Yes	Determines Location (Lat/Long)

This dual system makes evolutionary sense.

• The Compass must be consulted constantly (second-by-second) to maintain a heading while swimming. Integrating this into the visual system (as a "heads-up display" of direction) allows for rapid course correction.

• The Map is consulted less frequently (perhaps daily or hourly) to check global position. Magnetite is an ideal sensor for measuring intensity (a scalar value), which is a key component of the map. Cryptochrome, which detects the angle of field lines relative to light, is less suited for measuring absolute intensity. Thus, the turtle "sees" its direction but "feels" its location.⁹

6.3 Integration with Previous Research

This study resolves decades of ambiguity. Previous work had shown that sea turtle orientation (compass) is light-dependent, suggesting a cryptochrome mechanism.⁹ However, the map sense involves detecting intensity, which cryptochrome models struggle to explain. By confirming that the map is pulse-sensitive (and thus magnetite-based), the Mackiewicz study harmonizes these disparate findings into a coherent physiological model.

7. Comparative Navigation: A Universal Toolkit?

The discovery of a magnetite-based map in sea turtles does not exist in a vacuum. It aligns with a growing body of evidence across the animal kingdom, suggesting that the "Two-Sense" solution might be a convergent evolutionary trait among long-distance migrants.

7.1 The Salmon Connection

Research on Chinook salmon (Oncorhynchus tshawytscha) has paralleled the findings in turtles. In studies led by Nathan Putman and David Noakes (often collaborating with the Lohmanns), juvenile salmon subjected to magnetic pulses showed disrupted orientation when tested in "map-shifted" magnetic fields, but not in local fields.²⁹

• Parallels: Like turtles, salmon use magnetic cues to navigate vast oceanic distances (the Pacific vs. the Atlantic). The fact that pulses disrupt their ability to navigate to distant virtual locations suggests they too use a magnetite-based map.

• Anatomy: In salmonids, magnetite crystals have been identified in the olfactory epithelium (nose), suggesting a connection between the sense of smell and the magnetic map—a different anatomical solution than birds but functionally similar.²¹

7.2 The Avian Puzzle

Birds, the most studied navigators, offer a complex comparison.

• The Compass: There is overwhelming evidence that the avian magnetic compass is light-dependent and located in the right eye, mediated by cryptochrome. It is insensitive to pulses.¹⁹

• The Map: Evidence suggests the avian map is mediated by magnetite. Pulse experiments on bobolinks and other migrants have disrupted map-based navigation behaviors while leaving the compass intact.³² However, the anatomical location of the magnetite remains controversial. Early claims of magnetite in the pigeon beak were challenged when the cells turned out to be macrophages (immune cells) rather than neurons.¹⁷ Despite the anatomical uncertainty, the behavioral evidence of a pulse-sensitive map in birds aligns perfectly with the new turtle data.

7.3 Invertebrate Convergences

The universality of magnetite extends to invertebrates. Spiny lobsters (Panulirus argus), which also migrate long distances on the seafloor, have shown susceptibility to magnetic pulses, disrupting their homing ability.⁸ Even magnetotactic bacteria use magnetite chains to orient. This ubiquity suggests that biogenic magnetite is an ancient, fundamental biological adaptation to the geomagnetic field, which vertebrates later specialized into a high-precision map sensor.

8. Conservation in the Anthropocene: The Electromagnetic Threat

The realization that sea turtles rely on a delicate, magnetite-based "feeling" to navigate the ocean has profound and alarming implications for marine conservation. We are entering an era of unprecedented electromagnetic pollution in the marine environment, and the Mackiewicz study suggests we may be inadvertently blinding these animals.

8.1 The Threat of Ferrous Infrastructure

Conservation efforts often involve protecting sea turtle nests from predators (raccoons, foxes) using wire cages.

• The Problem: If these cages are made of ferrous metal (iron, steel), they distort the local magnetic field. Research has shown that these distortions can be significant enough to alter the magnetic "imprinting" of hatchlings.⁷

• Imprinting: Hatchlings are thought to memorize the magnetic signature of their natal beach to return years later. If they imprint on a distorted field caused by a steel cage, their internal map will be calibrated incorrectly. When they return 30 years later as adults, they may fail to find the beach.

• The Solution: The Mackiewicz study reinforces the urgent recommendation to use non-magnetic materials, such as plastic, aluminum, or marine-grade stainless steel (non-ferrous), for all nest protection structures.³³

8.2 Offshore Energy and Subsea Cables

The push for renewable energy is filling the coastal oceans with infrastructure.

• HVDC Cables: High-voltage direct current cables connecting offshore wind farms to the mainland generate significant magnetic fields. While buried, these fields can extend into the water column.

• The Disruption: For an animal that "feels" magnetic intensity to determine its location, swimming over a high-voltage cable could be the sensory equivalent of a blinding flash of light or a deafening noise. It represents a massive, unnatural anomaly in their magnetic map. While a cable is unlikely to permanently remagnetize their cells like a lab pulse, it could cause temporary spatial disorientation or "reset" their navigational calculations, potentially causing them to deviate from migratory corridors.⁶

8.3 Electromagnetic Smog (RFI)

While the map sense is sensitive to magnetic fields, the compass sense (cryptochrome) is sensitive to radiofrequency interference (RFI). Studies have shown that electrosmog in the AM radio band can disrupt the compass orientation of migratory birds.¹⁹ The Mackiewicz study notes that while RFI affects the compass, the pulse affects the map, meaning anthropogenic noise attacks both systems on different fronts. Urbanized coastlines, rich in both ferrous metal (seawalls, rebar) and electronic noise, create a "confusing" sensory landscape for hatchlings trying to start their journey.³⁵

9. Conclusion: The Dual-Sense Reality

The publication of Mackiewicz et al. (2025) marks a watershed moment in the discipline of sensory ecology. By ingeniously asking turtles to "dance" for their dinner, the researchers have moved the field of magnetoreception from theoretical speculation to behavioral demonstration.

The confirmation that the sea turtle's magnetic map relies on a magnetite-based receptor fundamentally changes our understanding of these animals. They are not merely observing the world; they are physically connected to the planet's geophysics, feeling the subtle tug of the pole and the intensity of the crustal field. This "Two-Sense" reality—a visual compass and a tactile map—reveals a level of biological sophistication that evolutionary pressures have honed over millions of years to conquer the featureless blue desert of the Atlantic.

However, this discovery comes with a burden of responsibility. As we now understand the mechanism, we also understand its vulnerability. The "feeling" sense of the turtle is susceptible to the iron and electricity of human industry. Preserving these ancient mariners requires more than just protecting their nesting beaches from development; it requires preserving the invisible, magnetic sanctity of their migratory corridors. We must ensure that the map they have evolved to read remains legible, lest we erase the coordinates of their survival.

Technical Appendix: Comparative Data

Table 1: Summary of Behavioral Response to Magnetic Pulse in Caretta caretta

Treatment Group	Handling Procedure	Magnetic Pulse Applied?	Behavioral Outcome in Rewarded Field	Interpretation
Control	Standard handling	No	High frequency of "dancing"	Map sense intact; recognition successful.
Sham	Placed in coil, no discharge	No	High frequency of "dancing"	Handling/noise does not disrupt map sense.
Experimental	Placed in coil, discharged	Yes (~85 mT)	Significantly reduced "dancing"	Map sense disrupted; recognition failed.
Data synthesized from Mackiewicz et al. (2025).3

Table 2: Comparative Magnetoreception Mechanisms in Migratory Species

Species	Compass Mechanism (Direction)	Map Mechanism (Location)	Pulse Sensitivity?	Reference
Loggerhead Turtle	Light-Dependent (Cryptochrome)	Magnetite-Based ("Feel")	Yes (Map only)	Mackiewicz et al. (2025)
Chinook Salmon	Unknown (likely Magnetite)	Magnetite-Based	Yes (Map/Orientation)	Putman et al. (2014); Noakes et al.
Homing Pigeon	Light-Dependent (Cryptochrome)	Magnetite-Based (Beak/Trigeminal)	Yes (Specific behaviors)	Wiltschko et al. (2007)
Spiny Lobster	Unknown	Magnetite-Based	Yes	Lohmann et al. (1995)

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