Moth vs. Bat: How Lucerne Moths Use Erratic Flight to Dodge Echolocation
"New research reveals the surprising escape tactics of lucerne moths, highlighting their ability to evade bats with unpredictable flight patterns."
The nighttime world is a battleground, especially for insects facing predators that hunt by sound. Bats, masters of echolocation, send out ultrasonic pulses to navigate and find their prey. In response, many moths have developed ultrasound-sensitive hearing to detect these signals and evade capture. The stakes are high: survival depends on outsmarting these aerial hunters.
Typically, when a moth hears the faint cries of a distant bat, it might make a slight turn to steer clear. But when a bat gets closer, emitting louder and more frequent pulses, moths often resort to erratic, unpredictable flight. Some even cease flying altogether, diving to the ground in a last-ditch attempt to escape. But not all moths follow this pattern.
A recent study focuses on the lucerne moth (Nomophila nearctica) and its unique evasion strategy. Unlike many moths, the lucerne moth rarely dives in response to bat echolocation. Instead, it relies on early and erratic flight maneuvers, regardless of how close the bat is. This approach challenges traditional understanding of moth behavior and highlights the diversity of survival tactics in the insect world.
Lucerne Moths’ Evasive Response
The lucerne moth, Nomophila nearctica, did not make passive dives when exposed to frequent, loud ultrasonic pulses above 60 dB SPL simulating the attack calls of the big brown bat, Eptesicus fuscus. Instead, it turned away or flew erratically. Research on noctuid moths also reports ultrasound-sensitive ears that provide information about threats from different sympatric bat species. The supplied sources describe these behaviors and sensory adaptations but provide no population or impact statistics.
Bat Call Monitoring and Predator Countermeasures
Acoustic identification of bat echolocation calls is a cornerstone of bat research and conservation, but a systematic review of 531 articles published between 1990 and 2025 says the reliability of automated identification methods remains uncertain. In predator–prey research, earlier work suggested that some bats use low-amplitude “stealth” echolocation to counter moth hearing. However, conclusive evidence for bat counterstrategies against insect defenses has been difficult to acquire. Eared insects may evade calls, while some tiger moths produce sounds that deter bats during aerial attacks.
Milestones in Echolocation Research
A 2018 review surveys important milestones in the discovery and early understanding of bat echolocation through about the mid-1980s, describing the field’s understanding of behavioral and neural adaptations as a major achievement of neuroethology. A separate 2015 study found that luna moth hindwing tails lured bat attacks toward those wing regions in 55% of interactions with intact moths. The researchers’ flight-kinematics analysis suggested that the tails play only a minimal role in flight performance.
Lucerne Moths: Early Dodging Experts
Researchers at the University of Toronto Scarborough investigated how lucerne moths respond to simulated bat echolocation calls. They found that these moths consistently turned away or flew erratically when they detected ultrasonic pulses above a certain intensity, no matter the specific pattern or frequency of the calls. This indicates that lucerne moths prioritize early action over last-minute desperate measures.
- No Response: The moth continued flying without any noticeable change in direction or flight pattern.
- Turning-Away Response: The moth altered its course to fly away from the source of the ultrasonic sound.
- Erratic Response: The moth exhibited unpredictable flight patterns, such as looping, zigzagging, or spiraling.
Ultrasonic Avoidance Research
A 2025 study examines how ultrasonic pulse timing elicits escape responses in cabbage looper moths, Trichoplusia ni, using tethered, flying moths of both sexes and host-searching mated females. The supplied snippet says behavioral responses in nocturnal predator–prey interactions remain unclear. It also notes prior findings that ultrasonic pulses can suppress flight in the lucerne moth, Nomophila nearctica, and the Asian corn borer, Ostrinia furnacalis, both crambid moths. The sources provided do not report the 2025 study’s results.
Erratic Flight Instead of Passive Diving
In tests of the lucerne moth, Nomophila nearctica, frequent, loud ultrasonic pulses above 60 dB SPL simulating an attacking Eptesicus fuscus did not trigger passive dives. The moths instead turned away or flew erratically, regardless of the stimulus’s temporal structure. A related-family comparison reports that tethered Asian corn borer moths, Ostrinia furnacalis, showed evasive action in about 80% of individuals exposed to 62-dB ultrasonic pulses, despite not making substantial numbers of passive dives. These findings show that evasion can occur without the stereotyped diving response.
Why Early Evasion Works
This early escape strategy might be particularly effective because bats can track and catch erratically flying moths. By initiating unpredictable flight early, the lucerne moth increases its chances of avoiding capture, blending into cluttered environments, or simply exhausting the bat's pursuit.
While diving might seem like a foolproof last resort, it’s risky. Bats are adept at catching diving moths, making early, evasive maneuvers a more reliable survival tactic for lucerne moths. This behavior is advantageous, particularly because these moths often fly close to the ground, where vegetation provides additional cover.
The lucerne moth's strategy highlights the complexity of predator-prey relationships and the diverse ways in which animals adapt to survive. Further research into other moth species could reveal even more unique strategies in the ongoing battle between bats and their insect prey.