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DUAL FUNCTION OF TIGER MOTH TYMBAL SOUND: SONAR JAMMING AND COURTSHIP SIGNALLING

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title
DUAL FUNCTION OF TIGER MOTH TYMBAL SOUND: SONAR JAMMING AND COURTSHIP SIGNALLING
author
Fernandez Delgado, Yohami
abstract
The ancient arm-race between bats and insects has provided selective pressure on both predator and prey for the last 65 million years. Bats have evolved a biological sonar to navigate space and pursue their prey items, in complete darkness. Tiger moths (Erebidae: Arctiinae) in response, have developed hearing structures tuned to the ultrasonic cries of their predators and evolved diverse escape maneuvers and sound production. Some species have gone one step further and tymbal sounds play a role in courtship and sexual selection. Chapter one provides an overview of the dual functions of acoustic signals in tiger moths.In chapter two, I address the hypothesis that the temporal properties of tiger moth signals (i.e duty cycle) influence the effectiveness of the jamming defense. I analyze the capture rate of big brown bats (Eptesicus fuscus) attacking tethered moths when challenged with modified signals of Bertholdia trigona. Moth sounds were effective at decreasing predation success and this effect was stronger for high duty cycle signals. I discovered that the jamming ability of tiger moth clicks is a continuous function of duty cycle. I also include evidence of acoustic counter-strategies in bats to compensate for sonar jamming. Chapter three reports for the first time the effect of jamming at the neuronal level using tiger moth natural sounds. I recorded single units from the inferior colliculus of big brown bats. Neurons responded to both conspecific echolocation pulses and tymbal sounds. I examined how the neural firing pattern evoked in response to echolocation calls varied in the presence of masking tymbal sounds with different duty cycles. Duty cycles of 25% and 45% strongly disrupt the neural response. I found evidence that the three phases of the echolocation sequence (search, approach and terminal buzz) were all susceptible to the jamming effect. The spike rates of collicular neurons in contrast, were not affected by the spectral motion (direction of frequency modulation) of moth clicks. In chapter four I determined whether the characteristics of moth sounds that make them effective sonar jammers also promote courtship success. I combined 1) behavioral observations of the acoustic courtship of B. trigona and Carales arizonensis with 2) playback experiments to assess female acoustic preference; and 3) female choice experiments. I demonstrated that acoustic communication impacts mating success in B. trigona and C. arizonensis differently. In C. arizonensis acoustic emissions were not frequent during courtship and females mated with males regardless of their sound production capabilities. For B. trigona however, I recorded acoustic emissions in every mating attempt and females showed strong preference towards high duty cycle signals during playback experiments. Males mating success decreased when tymbal sound production was partially or completely prevented experimentally.
subject
acoustic communication
courtship
duty cycle
echolocation
jamming
tiger moths
contributor
Conner, William E (committee chair)
Fuxjager, Matthew J (committee member)
Ashley-Ross, Miriam (committee member)
Fahrbach, Susan E (committee member)
Silver, Wayne (committee member)
date
2022-05-24T08:36:03Z (accessioned)
2023-05-23T08:30:13Z (available)
2022 (issued)
degree
Biology (discipline)
embargo
2023-05-23 (terms)
identifier
http://hdl.handle.net/10339/100740 (uri)
language
en (iso)
publisher
Wake Forest University
type
Dissertation

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