Stealth coating enables for larger body size in a predator-prey arms
race
- Ralph Simon,
- Alrike Dreissen,
- Helene Leroy,
- Matty Berg,
- Wouter Halfwerk
Abstract
Body size plays an important role in predator-prey interactions, but its
evolution is often limited due to all sorts of constraints. The arms
race between bats and moths provides great opportunities to study body
size evolution and associated traits across a wide range of species.
Nocturnally-active moths are in particular limited in evolving larger
bodies, as any increase in echo-acoustic reflective surface will put
them more at risk of a bat's sonar system. Here we assessed whether
moths can escape bat detection in a size-dependent way by increasing
their acoustic camouflage through ultrasonic absorptive body scales. We
used an automated setup to 3D scan a total of 110 moth specimen, from
eight different families of Lepidoptera using a biomimetic bat head. We
carried out three different ensonification experiments with intact,
partially shaved and fully shaved moth specimen to relate the level of
acoustic camouflage to various body size measurements. Comparing shaved
versus intact specimen we found a clear reduction in target strength,
although the effect strongly depends on frequency range as well as body
size. The stealth coating provided by sound absorptive body scales can
reduce prey detectability up to 365 cubic metres and is in particular
beneficial to larger species. The level of acoustic camouflage did not
covary with other anti-predator traits, such as ultrasonic ears and
appears to be an all-round anti-predator strategy. Acoustic camouflage
through stealth coating thus allows moths to escape from the allometric
relationship between size and detection risk, thereby enabling species
to evolve larger bodies.