Bats avoid radar installations: could electromagnetic fields deter bats from colliding with wind turbines?

Abstract

Large numbers of bats are killed by collisions with wind turbines, and there is at present no direct method of reducing or preventing this mortality. We therefore determine whether the electromagnetic radiation associated with radar installations can elicit an aversive behavioural response in foraging bats. Four civil air traffic control (ATC) radar stations, three military ATC radars and three weather radars were selected, each surrounded by heterogeneous habitat. Three sampling points matched for habitat type and structure, dominant vegetation species, altitude and surrounding land class were located at increasing distances from each station. A portable electromagnetic field meter measured the field strength of the radar at three distances from the source: in close proximity (<200 m) with a high electromagnetic field (EMF) strength >2 volts/metre, an intermediate point within line of sight of the radar (200-400 m) and with an EMF strength <2 v/m, and a control site out of sight of the radar (>400 m) and registering an EMF of zero v/m. At each radar station bat activity was recorded three times with three independent sampling points monitored on each occasion, resulting in a total of 90 samples, 30 of which were obtained within each field strength category. At these sampling points, bat activity was recorded using an automatic bat recording station, operated from sunset to sunrise. Bat activity was significantly reduced in habitats exposed to an EMF strength of greater than 2 v/m when compared to matched sites registering EMF levels of zero. The reduction in bat activity was not significantly different at lower levels of EMF strength within 400 m of the radar. We predict that the reduction in bat activity within habitats exposed to electromagnetic radiation may be a result of thermal induction and an increased risk of hyperthermia.

AI evidence extraction

Main findings

Bat activity was significantly reduced at sampling points with EMF strength >2 V/m (<200 m from radar) compared with matched control sites registering 0 V/m (>400 m, out of sight). Bat activity at lower EMF levels (<2 V/m within 200–400 m, line of sight) was not significantly different from control.

Outcomes measured

• bat activity (acoustic recordings)
• aversive behavioural response/avoidance near radar

Limitations

• Frequency characteristics of the radar exposure were not reported in the abstract.
• Observational field design; potential for residual confounding despite habitat matching.
• Mechanism (thermal induction/hyperthermia) is speculative/predicted rather than directly measured.

Suggested hubs

• occupational-exposure (0.2)
  Involves radar EMF sources, though the study focuses on wildlife rather than workers.

{
    "study_type": "exposure_assessment",
    "exposure": {
        "band": null,
        "source": "radar installations (air traffic control, military ATC, weather radar)",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "sunset to sunrise (bat activity recording)"
    },
    "population": "foraging bats (wild)",
    "sample_size": 90,
    "outcomes": [
        "bat activity (acoustic recordings)",
        "aversive behavioural response/avoidance near radar"
    ],
    "main_findings": "Bat activity was significantly reduced at sampling points with EMF strength >2 V/m (<200 m from radar) compared with matched control sites registering 0 V/m (>400 m, out of sight). Bat activity at lower EMF levels (<2 V/m within 200–400 m, line of sight) was not significantly different from control.",
    "effect_direction": "harm",
    "limitations": [
        "Frequency characteristics of the radar exposure were not reported in the abstract.",
        "Observational field design; potential for residual confounding despite habitat matching.",
        "Mechanism (thermal induction/hyperthermia) is speculative/predicted rather than directly measured."
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "bats",
        "radar",
        "electromagnetic fields",
        "EMF strength",
        "avoidance behavior",
        "wind turbines",
        "collision mitigation",
        "field study"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.200000000000000011102230246251565404236316680908203125,
            "reason": "Involves radar EMF sources, though the study focuses on wildlife rather than workers."
        }
    ]
}

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