Animal navigation: a noisy magnetic sense?

The Journal of experimental biology · 2020 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 2293

Study snapshot

PublicationThe Journal of experimental biology · 2020

Study typereview

Reported directionUnclear

Evidence ratingInsufficient

Abstract

Animal navigation: a noisy magnetic sense? Sönke Johnsen, Kenneth J Lohmann, Eric J Warrant. Animal navigation: a noisy magnetic sense? Journal of Experimental Biology 2020 223: jeb164921 doi: 10.1242/jeb.164921 Published 23 September 2020. Abstract Diverse organisms use Earth's magnetic field as a cue in orientation and navigation. Nevertheless, eliciting magnetic orientation responses reliably, either in laboratory or natural settings, is often difficult. Many species appear to preferentially exploit non-magnetic cues if they are available, suggesting that the magnetic sense often serves as a redundant or 'backup' source of information. This raises an interesting paradox: Earth's magnetic field appears to be more pervasive and reliable than almost any other navigational cue. Why then do animals not rely almost exclusively on the geomagnetic field, while ignoring or downplaying other cues? Here, we explore a possible explanation: that the magnetic sense of animals is 'noisy', in that the magnetic signal is small relative to thermal and receptor noise. Magnetic receptors are thus unable to instantaneously acquire magnetic information that is highly precise or accurate. We speculate that extensive time-averaging and/or other higher-order neural processing of magnetic information is required, rendering the magnetic sense inefficient relative to alternative cues that can be detected faster and with less effort. This interpretation is consistent with experimental results suggesting a long time course for magnetic compass and map responses in some animals. Despite possible limitations, magnetoreception may be maintained by natural selection because the geomagnetic field is sometimes the only source of directional and/or positional information available. pubmed.ncbi.nlm.nih.gov

Machine Enhanced Logic

AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typereview

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

ExposureNot supplied

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

The authors discuss that many animals use Earth's magnetic field for orientation/navigation but that magnetic orientation responses can be difficult to elicit reliably. They propose that animal magnetic sensing may be "noisy" (magnetic signal small relative to thermal and receptor noise), potentially requiring time-averaging and/or higher-order neural processing, consistent with experimental results suggesting long time courses for magnetic compass/map responses in some animals.

Outcomes measured

animal orientation and navigation using geomagnetic cues
magnetoreception signal-to-noise limitations (thermal/receptor noise)
time course/processing requirements for magnetic compass and map responses

Limitations

Narrative/speculative elements are explicitly noted ("We speculate")
No specific methods, inclusion criteria, or quantitative synthesis described in the abstract
No exposure quantification or standardized outcome measures provided in the abstract

View raw extracted JSON

{
  "study_type": "review",
  "exposure": {
    "band": null,
    "source": "Earth's magnetic field (geomagnetic field)",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "animal orientation and navigation using geomagnetic cues",
    "magnetoreception signal-to-noise limitations (thermal/receptor noise)",
    "time course/processing requirements for magnetic compass and map responses"
  ],
  "main_findings": "The authors discuss that many animals use Earth's magnetic field for orientation/navigation but that magnetic orientation responses can be difficult to elicit reliably. They propose that animal magnetic sensing may be \"noisy\" (magnetic signal small relative to thermal and receptor noise), potentially requiring time-averaging and/or higher-order neural processing, consistent with experimental results suggesting long time courses for magnetic compass/map responses in some animals.",
  "effect_direction": "unclear",
  "limitations": [
    "Narrative/speculative elements are explicitly noted (\"We speculate\")",
    "No specific methods, inclusion criteria, or quantitative synthesis described in the abstract",
    "No exposure quantification or standardized outcome measures provided in the abstract"
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "magnetoreception",
    "geomagnetic field",
    "animal navigation",
    "orientation",
    "sensory noise",
    "time-averaging",
    "neural processing"
  ],
  "suggested_hubs": []
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1242/jeb.164921
PubMed: 32967977

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