Highlights

  • ΒιΆΉΣ³»­΄«Γ½ researchers discovered that electric eels and their knifefish prey use electric stealth, strategically turning their electric signals on and off to sense their environment while avoiding detection.

  • Field and laboratory data show knifefish go electrically silent when eels are nearby, while eels briefly pause low-voltage signals before striking, minimizing the chance of alerting prey.

  • The findings reveal a broader principle seen in nature and technology: successful sensing systems β€”Β  from animals to sonar and radar β€” must balance gathering information with staying hidden.

In aquatic ecosystems, some species use active sensing systems, emitting echolocation sounds or electric fields to navigate dark or murky waters.

This sensory ability can come with trade-offs. For electric eels and their weakly electric knifefish prey, generating electric fields helps them navigate and hunt, but those same signals can also reveal their location.

In a recent study published in , ΒιΆΉΣ³»­΄«Γ½ researchers found that both electric eels and knifefish strategically suppress and resume their electric signals to avoid detection.

The findings provide new insight into how animals balance sensing their surroundings while remaining hidden from predators or prey, a challenge that also appears in technologies such as sonar and radar. This work also expands scientific understanding of how active sensory systems evolve in competitive environments where being detected can mean losing a meal or becoming one.

β€œOur findings show that active sensing creates a paradox: the same electric signals these animals need to navigate and hunt can also reveal them to eavesdropping predators or prey,” says Professor of Biology William Crampton, who co-led the study with biology doctoral graduate Lok Poon ’26PhD. β€œBoth eels and knifefish appear to resolve this paradox through electric stealth, briefly suppressing their signals when concealment matters, then resuming them when sensing becomes more important.”

Researcher Lok Poon stands outdoors carrying field equipment in a wooded area.
ΒιΆΉΣ³»­΄«Γ½ biology doctoral graduate Lok Poon ’26PhD holding electric signal loggers designed by Crampton Lab, which are used to record wild electric fish activity in the Amazon. (Photo by William Crampton)

Tracking Electric Signals in the Amazon

To test these predator-prey interactions, the researchers deployed six custom-designed electric signal loggers along a 150-meter section of an Amazonian stream. Each logger recorded 60-second segments of electric signals over 27 nights. In total, nearly 107,000 minutes of data were collected.

β€œElectric fish are ideal for this kind of study because their signals let us monitor their presence and movements electronically, simply by recording how often they pass near submerged electrodes,” Crampton says. β€œOur loggers allowed us, for the first time, to monitor predator-prey electric signaling interactions continuously in the wild.”

Researchers then analyzed the recordings to distinguish species by their unique electric signal signatures.

How Eels and Knifefish Use β€œElectric Stealth”

“With knifefish, we found that when they detect electric eel signals, some flee while some pulse-type species switch off their own electric discharges for several seconds. “β€”William Crampton, professor of biology

β€œWith knifefish, we found that when they detect electric eel signals, some flee while some pulse-type species switch off their own electric discharges for several seconds,” Crampton says. β€œIn our logger recordings, a knifefish could be producing its normal train of pulses to sense its environment, then suddenly become electrically silent as soon as eel signals appeared.”

Laboratory tests showed that low-frequency components of electric eel signals play a key role in triggering this response, with knifefish reacting far less when those components were reduced.

Electric eels were also found to pause their low-voltage electrolocation pulses before high-voltage bursts used to probe for or stun prey. This silence would make an approaching eel less detectable to electroreceptive prey such as knifefish. Once the eel produces a high-voltage burst, however, it has revealed its presence, temporarily reducing the benefit of stealth.  The eel promptly resumes its regular low-voltage pulses, likely to rapidly relocate, track or capture prey.

Professor William Crampton monitors recording equipment beside a water-filled tank during a nighttime field study.
Professor of Biology Will Crampton recording electric signals from weakly electric fishes in temporary captivity. (Photo by Lok Poon ’26 PhD)

β€œThe field recordings revealed these phenomena in the ecological context,” Crampton says. β€œThe laboratory experiments then allowed us to isolate the eel signal features that trigger knifefish responses.”

Parallels in Nature and Technology

In nature, the only well-studied comparison to this behavior is the predator-prey dynamic between killer whales and their toothed-whale prey.

β€œKiller whales and smaller toothed whales such as beaked whales use echolocation, relying on sound rather than electric signals to sense their surroundings,” Crampton says. β€œMammal-eating killer whales can suppress echolocation and calls while hunting, while beaked whales and other prey species may reduce vocal activity or take evasive action when they detect killer whale sounds. The eel-knifefish system shows a remarkably similar trade-off in the electric sense.”

The findings suggest convergent evolutionary pressures favoring the ability of both predators and prey to modulate active-sensing signals to improve survival.

Similar trade-offs also occut in human active-sensing technologies such as sonar and radar. A submarine, for instance, can use active signals to detect its surroundings, but each outgoing ping can also reveal the vessel’s location.

β€œJust as we found in electric eels and knifefish, operators of these systems balance the need to gather information with the need to remain hidden,” Crampton says. β€œIn submarines, that can mean alternating between active sonar and passive listening depending on the situation.”

Electric eels, knifefish, echolocating whales and human operators all face the same challenge: balancing the benefits of active sensing with the risk of detection.

Future Research Applications

Electric fish have long contributed to scientists’ understanding of concepts beyond biology, including electricity, nerves and sensing.

β€œElectric fishes have played an outsized role in the history of biology and physics,” Crampton says. β€œFor example, their discharges helped shape early research on electricity, including Alessandro Volta’s invention of the first battery, and their electric organs later became important model tissues for studying acetylcholine receptors β€” protein channels that help nerves send signals to other cells.”

The new findings build on this legacy, showing how electric fish can reveal principles related to sensing, stealth and decision making. Similar trade-offs shape sonar, radar and autonomous sensing technologies, suggesting that nature’s solutions to stealth and detection may offer insights for future adaptive sensing systems.

β€œThis study shows that active sensing is not just about gathering information, but also about managing the risk of being detected,” Crampton says. β€œThis opens opportunities for future research, from understanding how other aquatic species respond to electric signals to uncovering whether similar stealth strategies occur in other sensory systems.”

This work was funded by National Science Foundation Graduate Research Fellowship Program grant 2035702 (L.P.), an American Philosophical Society Lewis and Clark Fund for Exploration and Field Research grant (L.P.), and National Science Foundation grant DEB-1146374 (W.G.R.C.).