Publication Date

8-2017

Date of Final Oral Examination (Defense)

6-29-2017

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Biology

Department

Biology

Supervisory Committee Chair

Jesse R. Barber, Ph.D.

Supervisory Committee Member

Jennifer Forbey, Ph.D.

Supervisory Committee Member

James F. Smith, Ph.D.

Abstract

Prey-generated illusions span sensory systems. Previous studies have mainly focused on visual illusions presented by prey coloring or morphology, but few have explored illusions produced via sound. We investigate an acoustic sensory illusion in moths, created by complex hindwing structures that divert echolocating bat predators. A phylogeny of the moth family, Saturniidae, in combination with data from geometric morphometrics, reveals that hindwings have repeatedly elongated to form tails across evolutionary time. Using high-speed, multi-camera, synchronized videos of bat-moth battles, we quantified the selective pressure of predation on extant and experimentally-modified moths, defined by moth escape success from bat attack. We approximated a gradient of less derived to more derived non-tailed Saturniidae morphs using Antheraea polyphemus, by reducing hindwing area (reduced), maintaining hindwing area (intact, sham) and adding hindwing area (elongated). We performed similar alterations along a potential evolutionary gradient with two tailed species, Actias luna and Argema mimosae, by removing the tails (ablated), shortening the tails (shortened, blunt), maintaining the tails (intact, sham) or elongating the tails (elongated, A. luna only). With increasing tail length, moths had a greater chance of surviving bat attack (model slope = 0.18±0.05) and the longest-tailed moths (tails > 7cm) survived bat attack in more than 56% of battles. Bat attack was also diverted from a moth’s body to its hindwing region at increasing rates with increasing hindwing length (model slope = 0.31±0.05). Tailed moths drew bat attack either towards the body or tail ends in 75% of interactions and towards the hindwing in only 25% of interactions, thus providing support for an attack on multiple targets, rather than the center of a single enlarged echo. We also extracted the 3D flight paths of moths from these encounters and found that flight kinematics do not change across genera or treatments, nor are they associated with escape success. These data provide evidence supporting a sonar-specific sensory illusion of multiple targets, and a challenge to the physiological limits of bat echolocation.

DOI

https://doi.org/10.18122/B2W695

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