The influence of bat echolocation call duration and timing on auditory encoding of predator distance in noctuoid moths

2019

Functional Ecology

Many prey species overlap in time and space and are hunted by the same predators. A common anti‐predator behaviour is using evasive manoeuvres to escape an attacking predator. The escape‐tactic diversity hypothesis postulates that species‐specific differences in evasive behaviour will increase the overall unpredictability experienced by predators within a predator–prey community. Evolutionary, escape‐tactic diversity would be driven by the enhanced predator protection for each prey individual in the community. However, escape‐tactic diversity could also be a functional consequence of morphological differences that correlate with evasive capabilities. Echolocating bats and eared moths are a textbook example of predator–prey interactions. Moths exhibit evasive flight with diverse tactics; however, the variability of their evasive flight within and between species and individuals has never been quantified systematically. In addition, moth species show variation in size, which correlates with their flight capability. We recorded flight strength during tethered flight of eight sympatric moth species in response to the same level of simulated bat predation. Our method allowed us to record kinematic parameters that are correlated with evasive flight in a controlled way to investigate species‐specific differences in escape tactics. We show species‐specific and size‐independent differences in both overall flight strength and change of flight strength over time, supporting the escape‐tactic diversity hypothesis for eared moths. Additionally, we show strong interindividual differences in evasive flight within some species. This diversity in escape tactic between eared moths increases the overall unpredictability of evasive flight experienced by bat predators, likely providing increased protection against predatory bats for the single individual.

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Stimulusmentioning

confidence: 99%

Section: Stimulusmentioning

confidence: 99%

See 3 more Smart Citations

Species‐specific strategies increase unpredictability of escape flight in eared moths

Hügel

2019

Functional Ecology

Light might suppress both types of sound‐evoked antipredator flight in moths

Hügel

2020

Ecology and Evolution

Urbanization exposes wild animals to increased levels of light, affecting particularly nocturnal animals. Artificial light at night might shift the balance of predator-prey interactions, for example, of nocturnal echolocating bats and eared moths. Moths exposed to light show less last-ditch maneuvers in response to attacking close-by bats. In contrast, the extent to which negative phonotaxis, moths' first line of defense against distant bats, is affected by light is unclear. Here, we aimed to quantify the overall effect of light on both types of sound-evoked antipredator flight, last-ditch maneuvers and negative phonotaxis. We caught moths at two light traps, which were alternately equipped with loudspeakers that presented ultrasonic playbacks to simulate hunting bats. The light field was omnidirectional to attract moths equally from all directions. In contrast, the sound field was directional and thus, depending on the moth's approach direction, elicited either only negative phonotaxis, or negative phonotaxis and last-ditch maneuvers. We did not observe an effect of sound playback on the number of caught moths, suggesting that light might suppress both types of antipredator flight, as either type would have caused a decline in the number of caught moths. As control, we confirmed that our playback was able to elicit evasive flight in moths in a dark flight room. Showing no effect of a treatment, however, is difficult. We discuss potential alternative explanations for our results, and call for further studies to investigate how light interferes with animal behavior.

Neural representation of bat predation risk and evasive flight in moths: A modelling approach

Journal of Theoretical Biology

Hofstede

Holderied

2020

Self Cite

Most animals are at risk from multiple predators and can vary anti-predator behaviour based on the level of threat posed by each predator. Animals use sensory systems to detect predator cues, but the relationship between the tuning of sensory systems and the sensory cues related to predator threat are not well-studied at the community level. Noctuid moths have ultrasoundsensitive ears to detect the echolocation calls of predatory bats. Here, combining empirical data and mathematical modelling, we show that moth hearing is adapted to provide information about the threat posed by different sympatric bat species. First, we found that multiple characteristics related to the threat posed by bats to moths correlate with bat echolocation call frequency. Second, the frequency tuning of the most sensitive auditory receptor in noctuid moth ears provides information allowing moths to escape detection by all sympatric bats with similar safety margin distances. Third, the least sensitive auditory receptor usually responds to bat echolocation calls at a similar distance across all moth species for a given bat species. If this neuron triggers last-ditch evasive flight, it suggests that there is an ideal reaction distance for each bat species, regardless of moth size. This study shows that even a very simple sensory system can adapt to deliver information suitable for triggering appropriate defensive reactions to each predator in a multiple predator community.