13.4 - Electrical and Magnetic Senses

Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization

First Edition

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm

Nearly all organisms, including humans, emit direct-current electricity when swimming in ordinary seawater. This is due to the gradient in electrical potential between normal body fluids and the saline electrolytic ocean. Voltages are actually developed across different parts of the body.

Sharks -- rather large animals of low intelligence -- are sensitive to incredibly minute electric fields. They can detect the equivalent of a single flash light battery at a distance of 1500 kilometers (about 10^-8 volt/cm). A small wound can double a person’s voltage gradient in water, and sharks have no trouble sensing this.⁵⁷⁴

Intelligent extraterrestrials may have developed an electric sense, given the proper evolutionary environment. By maintaining a carefully shaped field around their bodies, such creatures could detect the entry of foreign objects and other lifeforms into its personal space. Electrosensitive aliens could clearly identify the exact nature of the intruder by noting the location, magnitude, and shape of the distortion in the static field. Also detectable are such nonbiological sources as motions of and compositional changes in seawater, subsurface ore concentrations, earthquakes, thunderstorms and other meteorological disturbances.

Many terrestrial animals use a kind of electropulse reflection system analogous to sonar. Such mechanisms have evolved independently on Earth at least six different times among fishes. The most familiar include the electric eel (Electrophorus electricus), the electric ray (Torpedo), the skate, the knifefishes, the electric stargazers (Astroscopus), and the electric catfish (Malapterurus electricus) of the Nile.

The electrosonar fishes generate pulses at regular intervals. Amplitudes rarely exceed a third of a volt, and the frequencies range from 55 Hz for the Gymnotid species Sternopygus macrurus up to 300 Hz for Eigenmannia.^474,2516 (Peak surge rates as high as 1600 Hz have been recorded, though.)

Sense organs located in the head of Gymnarchus niloticus respond to currents as small as 0.003 picoamperes and voltages as low as 0.15 microvolt/cm. Dr. Hans W. Lissmann of Cambridge University believes that this typical electric fish uses its 300 Hz electrosonar for navigation. Its natural habitat is the muddy waters of Ghanese rivers in Africa. Since light cannot penetrate, the organism is forced to rely heavily on its inboard electronics. The fish uses its electric sense both to avoid obstacles and to detect and capture prey.²⁵¹⁶

The knifefish Eigenmannia has been closely studied by marine biologists because it uses its electrical sensitivity for social communication as well as navigation. When two of these animals meet, each adjusts his frequency up or down to avoid jamming the signals sent out by the other. And these high-speed discharges aren’t simple sine waves; rather, they are rich in harmonic variability and might easily serve as highly sophisticated communication systems in more cerebral alien creatures.²⁵⁴⁵

Dr. Carl Hopkins of Rockefeller University in New York has studied the sex habits of the electrical fish Sternopygus. When the male of this species passes a female, his normally polite and mild-mannered electronic emissions suddenly become an impassioned tangle of impulses -- the chaotic mixture of harmonics and timing that are his love song to potential mates. Literally, the female "turns on" the male.²⁵⁴¹

The Mormoryd or "elephant trunk" fishes provide our last example of social electrics. These organisms send pulsed electrical messages to each other as a form of territorial display to warn off competitors. When a stranger intrudes on the home turf, the defender raises his frequency in angry protest. Mormoryds also show a distinct fondness for playful activity, and at least one researcher has documented what might be called a "listen mode" of behavior. In this mode, one fish attentively ceases all electrical emanations when certain of its fellows pass by.²⁵⁴⁰ Similar patterns of electrocommunication have been observed in Gymnotus carapo, a knifefish.²⁵⁵⁰

One major question remains: What kind of planetary environment might give rise to intelligent aquatic beings who relied primarily on an electric sense? As first Lissmann and later the Jonases have suggested, there would appear to be two basic requirements.

First, to evolve electrosensitivity as the preferred sensory modality, the medium in which the creature dwells should be quite dark. This must be a permanent (not diurnal, seasonal, or sporadic) condition. Otherwise, eyes are so useful that it would be very difficult to rule them out as the primary modality. Even Gymnarchus, living out its entire existence in darkened and perpetually muddy waters, has a set of weak, poorly-developed eyes which it uses to tell day from night.

Second, virtually all electrosensitive creatures on Earth live either in the ocean depths or in a turbid, fast-flowing watery habitat. If evolution is to favor these beings, the environment should probably be both dark and turbulent. Sonic senses would then be scrambled, vision virtually useless, and olfactory messages rapidly mixed, diluted, and swirled away. Electric field sensing could then become the sensation of choice.

So we might expect to find electric intelligences in the deep oceans of fast-spinning pelagic worlds. Another possibility could be a terrestrial planet with some oceans but which orbits a bright star at a great distance or a feeble star at a moderate distance. (Subjovian worlds might work well too.) A third alternative might be the dark side of a tidally-locked one-face planet located near the inside edge of the stellar habitable zone, a set of conditions likely to give rise to violent oceanic currents and turbulent winds.

How would electrosensitive ETs view their world? We can imagine that it would be an utterly alien environment compared to anything in normal human experience.

Sensations could be detected only at relatively close range due to the high electrical resistivity of water.^82,565 The creature’s immediate sensory universe might extend out to about 100 meters for small objects, perhaps to a kilometer for larger ones. It should be a simple matter for these creatures to locate and distinguish various objects. Electric field lines diverge from a poor conductor -- such as rubber, plastic, glass, and other insulators -- and converge toward good conductors -- such as metals. Tests with electrosensitive fishes have proven that they are capable of detecting tiny glass rods 2 millimeters in diameter which are optically invisible in water. Two objects of the same size and shape, but constructed of different materials, are also easily distinguished.²⁵¹⁶ Depending on the texture, conductivity, and chemical composition of the target, electrosensitive extraterrestrials might have an equivalent to our "color" which we could scarcely understand or appreciate.

The natural magnetic field of the planet, or submerged ferromagnetic ore lodes, would produce minute variations and distortions in the electrosensory field. A warmer or cooler layer in the watery medium could give rise to similar effects. And electrical impulses can play over the skin of an object or penetrate it to varying depths, permitting both interior and exterior views.

A related but more restricted sensory modality is the perception of magnetic fields. Zoologists have not yet found any creature on Earth capable of generating its own magnetism. Such ability cannot be ruled out elsewhere, since terrestrial fishes can generate electric fields and circulating electric fields give rise to magnetic ones. Nevertheless, the uniform absence of biomagnetism on this world seems to suggest that it may be restricted to a somewhat passive role elsewhere -- as on Earth.

The magnetic sense has been documented in the common mud snail (Nassarius)⁸² and in planarian worms.⁷⁶⁵ Magnetotaxis -- attraction to magnetic sources -- has also been clearly demonstrated in marsh bacteria and a few other microscopic species. These diminutive organisms have tiny chains of iron-rich beads incorporated within their bodies which allow them to orient themselves along Earth’s north-south axis and swim towards Magnetic North.²⁵¹⁸

Insects, too, make use of the planetary field. Bees are known to build their hives in perfect alignment parallel to Magnetic North. If a strong magnet is placed nearby, the insects obligingly construct their new home in accordance with the new distorted direction of the magnetic field vector. (In one experiment a deflection of more than 40° from true north was achieved in this manner.⁴³⁸) Some species of termites are similarly affected, building their nests either parallel or perpendicular to the geomagnetic field at that location.²¹⁹ These insects are believed to be sensitive to a mere 10^-5 gauss, yet to date no organs or receptors have been isolated that could serve in this capacity.

Finally, one of the leading theories of bird navigation holds that these avians (besides sighting on familiar landmarks and the stars²⁵³²) take some of their directional cues from the position of the planetary magnetic field. There is much recent experimental evidence that birds can respond to fields as weak as 10^-3 gauss (Earth’s field is about 0.5 gauss at the surface).^2517,2519 There is also some unconfirmed evidence of a tiny organ in the corner of the eyes of the homing pigeon which is sensitive to magnetic flux.⁷⁹

Magnetosensitivity may well serve in at least an auxiliary role for many extraterrestrial animal species.