Acoustic camouflage increases with body size and bat echolocation frequency range in a community of nocturnally-active Lepidoptera
Data files
Oct 12, 2023 version files 70.78 KB
Abstract
- Body size is an important trait in predator-prey dynamics as it is often linked to detection, as well as the success of capture or escape. Larger prey, for example, often runs higher risk of detection by their predators, which imposes stronger selection on their anti-predator traits compared to smaller prey.
- Nocturnal Lepidoptera (moths) vary strongly in body size, which has consequences for their predation risk, as bigger moths return stronger echoes for echolocating bats. To compensate for increased predation risk, larger moths are therefore expected to have improved anti-predator defences. Moths are covered by different types of scales, which for a few species are known to absorb ultrasound, thus providing acoustic camouflage. Here we assessed whether moths differ in their acoustic camouflage in a size-dependent way by focusing on their body scales and the different frequency ranges used by bats.
- We used a sonar head to measure 3D echo scans of a total of 111 moth specimens across 58 species, from eight different families of Lepidoptera. We scanned all the specimens and related their echo-acoustic target strength to various body size measurements. Next, we removed the scales covering the thorax and abdomen and scanned a subset of specimens again to assess the sound-absorptive properties of these scales.
- Comparing intact specimens with descaled specimens we found almost all species to absorb ultrasound, reducing detection risk on average by 8%. Furthermore, the sound absorptive capacities of body scales increased with body size suggesting that larger species benefit more from acoustic camouflage. The size-dependent effect of camouflage was in particular pronounced for the higher frequencies (above 29 kHz), with moth species belonging to large-bodied families consequently demonstrating similar target strengths compared to species from small-bodied families. Finally, we found the families to differ in frequency range that provided the largest reduction in detection risk, which may be related to differences in predation pressure and predator communities of these families.
- In general, our findings have important implications for predator-prey interactions across eco-evolutionary timescales and may suggest that acoustic camouflage played a role in body size evolution of nocturnally-active Lepidoptera.
README: Acoustic camouflage increases with body size and bat echolocation frequency range in a community of nocturnally-active Lepidoptera
https://doi.org/10.5061/dryad.66t1g1k73
Description of the data and file structure
The file contains three separate tabs that contain the data from the measurements on intact, partially descaled and fully descaled specimens.
- Intact specimen:
Specimen nr. refers to our collection, missing numbers were damaged specimens and therefore excluded from analysis.
Different body measurements (in mg or mm) are provided as well as target strength (TS) measurements (in dB values relative to an optimal reflector). TS values were either averaged over all measurement planes, ensonification angles and frequencies, or analysed within specific frequency bands (e.g. TS_19-29 = target strength within the 19 - 29 kHz band).
- partially descaled:
Data for a subset of intact specimens that were partially descaled on their thorax and abdomen by using sticky tapes. hair weight (in mg) refers to the difference in weight of the sticky tapes before and after descaling. Data from intact specimens was subtracted from TS measurements from tape-treated specimens to obtain differences (TS_diff) for the overall frequency range, as well as the 5 consecutive frequency bands.
- fully descaled:
Data for a subset of intact specimens that were fully descaled on their thorax and abdomen by using a razor blade. Data from intact specimen was subtracted from TS measurements from treated specimens to obtain differences (TS_diff) for the overall frequency range, as well as the 5 consecutive frequency bands.