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Reference — Sensing charge: how real animals find each other electrically

REF109 · r1 · 2026-09-06 · Reference Researcher · Reference, not a design proposal. Decides nothing. First revision. Written for the newly seated Combat/Enemies role. The Enemies roster is built almost entirely out of sensing and reacting to charge — a Carrier walks to the nearest reachable loose charge, a Spark is drawn to stored charge within a short range, a Grounder makes a device stop working for want of current. REF101 covered how real animals generate current. Nothing covered how they sense it, which is what this roster actually does. This is that half. Sources read: Enemies, Mechanics/Power and Attraction, Reference.

Proposes nothing. Sourced fact in the body; anything that follows for this project is set apart, labelled as inference, and belongs to the Combat/Enemies designer and the Lead. Real animals are not enemies in a game and nothing here says a real behaviour would play well.

1. There are two kinds of electroreception, and they answer different questions

From Wikipedia: Electroreception and electrogenesis:

Passive Active
What it does "the animal senses the weak bioelectric fields generated by other animals and uses it to locate them" "the animal senses its surrounding environment by generating weak electric fields… and detecting distortions in these fields"
Receptor type Ampullary, low frequency (below 50 Hz) Tuberous, high frequency (20–20,000 Hz)
Range Long, but only finds things that leak a field About one body length
Users Sharks, rays, sturgeon, lungfish, some amphibians Weakly electric fish — African elephantfishes, South American knifefishes

Passive sensing is extraordinarily sensitive. Sharks' ampullae of Lorenzini detect gradients "as low as 5 nV/cm" — described as "much more sensitive to electric fields than electroreceptive freshwater fish, and indeed than any other animal" (Ampullae of Lorenzini). For scale, set that beside REF101 §2's electrofishing figures: attraction begins around 0.1 V/cm, which is twenty million times the shark's threshold. Sensing a field and being moved by one are not remotely the same magnitude.

Active sensing reads conductivity. A weakly electric fish uses electrolocation to distinguish conducting from non-conducting objects.

Bearing (inference, for Combat/Enemies). The design already sorts the world into conductors and non-conductors — wet salvage conducts, modules do not, water carries and dry ground does not (REF101 §4a). A real sense exists whose entire job is to read exactly that distinction, at about one body length. An enemy that perceives the district as "conductive / not conductive" rather than "visible / not visible" is a documented sensory mode, not an invention. Whether the roster wants it is the designer's call.

2. Weak and strong are the same organ at two settings

"These fish create a potential usually smaller than one volt" — weakly electric fish, using discharges to navigate and hunt in murky water. Strongly electric fish, like the electric eel, instead use "stronger electric discharges… to stun prey", at 400–600 V (Wikipedia; Catania, The Astonishing Behavior of Electric Eels, open access).

The eel does both. It emits "low-voltage EODs for active electroreception" continuously while exploring, and switches to high-voltage discharges to hunt. Same animal, same organ, two jobs.

Bearing (inference). An enemy that emits a weak field to find things and a strong one to act is one creature with two modes, not two roster entries — and the mode it is in is legible from outside, because the two discharges differ enormously in magnitude. That is a real structure available to a roster that currently separates seeking behaviour and damaging behaviour across different enemies.

3. The doublet: a predator that makes a hidden target reveal itself

This is the most striking documented behaviour in the group, and it is the inverse of hiding.

A hunting eel emits "two high-voltage pulses with an interval of about 2 ms". The pulses act on the prey's motor neurons, not its muscles directly — shown by curare experiments, where blocking the nerve–muscle junction made fish immune. The result is an involuntary whole-body twitch in prey the eel cannot see, and the eel responds to that twitch within 20–40 ms (Catania, open-access review; original: The shocking predatory strike of the electric eel, Science, 2014).

So the eel has two remote-control modes: make hidden prey move so it can be found, and freeze prey once it has been found.

Bearing (inference). In this design the electrical relationship runs one way — the player energises things and the Flood is drawn to them. A real predator using a discharge to force a concealed target to give itself away is documented, and it is the exact inverse. Whether anything in the roster should do that is entirely the Combat/Enemies designer's and the Lead's call; it is recorded because it is real and because it is not an obvious idea to have unprompted.

4. Jamming avoidance: what real electric animals do when they interfere with each other

Two wave-discharging fish whose frequencies are close enough will each shift away from the other. From Wikipedia: Jamming avoidance response:

  • Triggered when a stimulus is within 5 Hz of the fish's own electric organ discharge frequency.
  • Stimuli above the fish's frequency push its own frequency down; stimuli below push it up.
  • Maximum shift about ±6.5 Hz.
  • Seen in South American Eigenmannia virescens and Apteronotus, and African Gymnarchus niloticus — evolved independently on two continents, converging on nearly identical neural machinery.

Bearing (inference). A roster in which several enemies emit, seek or hold charge has a collision problem: what happens when two of them want the same signal, or interfere with one another. Nature's answer is a small, local, legible rule — detect the conflict, move away from it by a bounded amount — and the fact that it evolved twice independently suggests it is a cheap solution to that problem rather than an exotic one. Offered as a shape, not a mechanic.

What this page does not claim

Not a proposal, not a mechanic, and not a claim that any real behaviour would be readable, fun or cheap. No claim that the roster is missing anything or that any enemy should change — the roster is the Combat/Enemies designer's and the Lead's, and this page reviews none of it. No engineering or feasibility claim; all gated. The four Bearing notes are labelled inferences and each names what it is inferred from.

Sources

Bookkeeping

Method. Encyclopedia articles and one open-access review by the researcher who did the work, read-only on 2026-09-06. The eel behaviour is sourced to Catania's own review rather than to press coverage of it, and the original Science paper is cited alongside. Nothing was built, prototyped or tested.

Stated limits. Wikipedia is a tertiary source and is used here for definitional and threshold material that it states with citations; the behavioural claims in §3 come from the primary literature. The comparison in §1 between a shark's 5 nV/cm detection threshold and electrofishing's 0.1 V/cm attraction threshold is arithmetic across two different measurements — one a sensory limit, one a behavioural response — and is offered as an order-of-magnitude contrast, not an equivalence.

Corrections. Kill any statement here with a counter-source and it goes.