DOI: 10.5061/dryad.66t1g1k73
title: Acoustic camouflage increases with body size and bat echolocation frequency range in a community of nocturnally-active Lepidoptera

description: 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.
description: # 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](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.