page_title: Evolutionary arms race
section_title: Bats and moths
hierarchical_section_title: Evolutionary arms race / Examples / Bats and moths
caption_attribution_description: Deutsch: Rufe einer Zwergfledermaus während des Beutefangs. Die Aufzeichnung zeigt 1,1&#160;Sekunden; die Spektrogrammdarstellung wurde aus der 20fach verlangsamt abgespielten Aufnahme erstellt ("Zeitdehnung"). Die (lineare) Y-Achse reicht von 0 bis 160&#160;kHz,. Die Aufnahme enstand am Westufer des Main-Donau-Kanals, nördlich von Fürth. Die zeitgedehnte Aufnahme kann als Audiodatei angehört werden. English: Echolocation calls of a Common Pipistrelle approaching prey. The spectrograph was created from a 20fold dilated recording covering a total of 1.1 seconds. The linear y-axis ranges from 0 to 160&#160;kHz. The recording was taken at the western bank of the en:Rhine–Main–Danube Canals, north of the city of en:Fürth. The time-dilated recording is available as audio file
context_page_description: In evolutionary biology, an evolutionary arms race is a struggle between competing sets of co-evolving genes, traits, or species, that develop adaptations and counter-adaptations against each other, resembling an arms race. These are often described as examples of positive feedback. The co-evolving gene sets may be in different species, as in an evolutionary arms race between a predator species and its prey, or a parasite and its host. Alternatively, the arms race may be between members of the same species, as in the manipulation/sales resistance model of communication or as in runaway evolution or Red Queen effects. One example of an evolutionary arms race is in sexual conflict between the sexes, often described with the term Fisherian runaway. Thierry Lodé emphasized the role of such antagonistic interactions in evolution leading to character displacements and antagonistic coevolution.
context_section_description: Bats have evolved to use echolocation to detect and catch their prey. Moths have in turn evolved to detect the echolocation calls of hunting bats, and evoke evasive flight maneuvers, or reply with their own ultrasonic clicks to confuse the bat's echolocation. The Arctiidae subfamily of Noctuid moths uniquely respond to bat echolocation in three prevailing hypotheses: startle, sonar jamming, and acoustic aposematic defense. All these differences depend on specific environmental settings and the type of echolocation call; however, these hypotheses are not mutually exclusive and can be used by the same moth for defense. 
  The different defense mechanisms have been shown to be directly responsive to bat echolocation through sympatry studies. In places with spatial or temporal isolation between bats and their prey, the moth species hearing mechanism tends to regress. Fullard et al. (2004) compared adventive and endemic Noctiid moth species in a bat-free habitat to ultrasound and found that all of the adventive species reacted to the ultrasound by slowing their flight times, while only one of the endemic species reacted to the ultrasound signal, indicating a loss of hearing over time in the endemic population. However, the degree of loss or regression depends on the amount of evolutionary time and whether or not the moth species has developed secondary uses for hearing. 
  Some bats are known to use clicks at frequencies above or below moths' hearing ranges. This is known as the allotonic frequency hypothesis. It argues that the auditory systems in moths have driven their bat predators to use higher or lower frequency echolocation to circumvent the moth hearing. Barbastelle bats have evolved to use a quieter mode of echolocation, calling at a reduced volume and further reducing the volume of their clicks as they close in on prey moths. The lower volume of clicks reduces the effective successful hunting range, but results in a significantly higher number of moths caught than other, louder bat species. Moths have further evolved the ability to discriminate between high and low echolocation click rates, which indicates whether the bat has just detected their presence or is actively pursuing them. This allows them to decide whether or not defensive ultrasonic clicks are worth the time and energy expenditure.
caption: Spectrogram of Pipistrellus pipistrellus bat vocalizations during prey approach. The recording covers a total of 1.1 seconds; lower main frequency ca. 45 kHz (as typical for a common pipistrelle). About 150 milliseconds before final contact time between and duration of calls are becoming much shorter ("feeding buzz"). 
  Corresponding audio file:
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