DOI: 10.5061/dryad.z8w9ghxkd
title: Ripple effects in a communication network: Anti-eavesdropper defence elicits elaborated sexual signals in rival males

description: Emitting conspicuous signals into the environment to attract mates comes
 with the increased risk of interception by eavesdropping enemies. As a
 defence, a commonly described strategy is for signallers to group together
 in leks, diluting each individual’s risk. Lekking systems are often highly
 social settings in which competing males dynamically alter their
 signalling behaviour to attract mates. Thus, signalling at the lek
 requires navigating fluctuations in risk, competition, and reproductive
 opportunities. Here, we investigate how behavioural defence strategies
 directed at an eavesdropping enemy have cascading effects across the
 communication network. We investigated these behaviours in the túngara
 frog (Engystomops pustulosus), examining how a calling male’s swatting
 defence directed at frog-biting midges indirectly affects the calling
 behaviour of his rival. We found that the rival responds to swat-induced
 water ripples by increasing his call rate and complexity. Then, performing
 phonotaxis experiments, we found that eavesdropping fringe-lipped bats
 (Trachops cirrhosus) do not exhibit a preference for a swatting male
 compared to his rival, but females strongly prefer the rival male.
 Defences to minimize attacks from eavesdroppers thus shift the mate
 competition landscape in favour of rival males. By modulating the
 attractiveness of signalling prey to female receivers, we posit that
 eavesdropping micropredators likely have an unappreciated impact on the
 ecology and evolution of sexual communication systems.
description: <em><strong>Rival
 male experiment</strong></em>
 In August 2017, we collected
 calling male túngara frogs 1 to 4 hours after sunset from breeding sites
 within 1.5 km of Smithsonian Tropical Research Institute facilities
 (Gamboa, Panamá; 9°07.0’N, 79°41.9’W). Frogs took part in behavioural
 experiments in a large outdoor flight cage (5×5×2.5 m) within 3 hours
 following capture and before midnight. Following protocols established by
 the American Society of Ichthyologists and Herpetologists
 (https://asih.org/animal-care-guidelines), after each experiment we
 weighed, measured and toe-clipped the frog (to prevent testing the same
 individual multiple times), and released him the following night at his
 collection location. The research reported here complied with University
 of Texas at Austin #s AUP-2015-00048, AUP-2017-00051 and AUP-2020-00034;
 STRI IACUC protocols 2017-0102-2020-A8, 2018-0411-2021;
 and República de Panamá
 permits SE/AO-1-17, SE/A-44-18, SE/A-40-19, SE/A 69-15 and
 SE/AH-2-6.
 <em><strong>Field
 recordings</strong></em>
 To sample the natural
 variation of swat and call ripples from calling male túngara frogs, we
 recorded ripples from six males (<em>n</em> = 2 i<em>n
 situ</em>; <em>n </em>= 4 in a planter tray filled with
 water from the breeding site, placed by the original calling site). We
 measured the frequency, velocity and displacement of the water ripples
 with a digital laser vibrometer (LDV; Polytech PDV-100; Velocity = 20
 mm/s, Low Pass = 22 kHz, High Pass = none). The laser was focused on a
 reflective marker floating on the water surface; its reflection is
 detected by the LDV, allowing measurement of the surface vibrational
 velocities. We recorded these measurements from the digital output of the
 LDV using a Marantz audio recorder (48 kHz sample rate, 24 bit). See
 Supplementary Materials for a full description of the recording setup. We
 analysed call ripples (52 samples from 6 males; range: min = 5, max = 13
 per male) and swat ripples (66 samples from 6 males; range: min = 5, max =
 15 per male) using the velocity measurements recorded from the LDV digital
 output. We also converted velocity data to displacement values for
 comparison with related studies that have used this variable to
 characterize call ripples in this species (e.g. [32,36]). All ripple characterization analyses were
 performed in MATLAB R2016a (https://www.mathworks.com) using custom code
 (Supplementary Materials). The vertical velocity of a swat ripple differed
 depending on the location of the sensor relative to the side of the body
 that swats (Figure S1, Supplementary Materials and R scripts for details
 of the analysis). We therefore tested calling behaviour in response to
 both high- and low-velocity swat ripples to determine male responses to
 the range of swat ripple intensities encountered in the wild. We used the
 point estimate of the median maximum velocity of all recorded swat ripples
 (5.84 mm/sec. peak-to-peak), which was between the 95% credible intervals
 for the median low- and high-intensity swat values, as a guide to
 calibrate low- and high-velocity swat playbacks. While there was variation
 across playbacks, the vast majority of calibration measurements were
 within the range measured from the field recordings (see Figures S2-3 and
 associated R scripts for further details). 
 <em><strong>Experimental
 setup</strong></em> For our ripple playback files, we used a total
 of three field recordings. These files represented the median dominant
 frequency and median maximum velocity of either a i) high-velocity swat,
 ii) low-velocity swat, or iii) call ripple. As playback of call ripples
 always co-occurred with an airborne call playback, we ensured that the
 call ripple accurately coincided with the airborne call component by
 synchronizing their playback to match the temporal profile of the field
 recording. For the airborne component of the multimodal call playback, we
 generated a call comprised of a whine with one chuck, as this is the most
 common call complexity observed in natural settings (see Supplementary
 Materials for details) [37,38]. Prior to an experiment, a male (n = 29 frogs; no
 males were from field recordings) was placed in a pool (2.6 × 2.1 m) of
 dechlorinated tap water. The male was contained within a ripple cage but
 could otherwise call freely. This ripple cage, used in a previous study of
 call-induced ripples, is acoustically transparent to low frequency ripples
 [33]. The cylindrical ripple cage (10.5 cm total
 diameter) consisted of a plastic, circular base and top held in place by
 three evenly spaced, vertical screws (~0.4 cm diam.). Monofilament fishing
 line (~0.36 mm thick) was strung vertically, encircling all sides of the
 plastic base and top (spaced ~0.25 cm apart creating an acoustically
 transparent cylinder 8 cm. in diameter) to prevent the frog from escaping.
 Once the male was consistently calling, he was presented with the first of
 four trials, which were presented in random order and separated by at
 least 1 minute of silence. The order of presentation did not affect male
 responses (Tables S1-2). Each trial consisted of a 1-minute silent control
 playback and 1-minute playback of one of the following treatments: i)
 high-intensity swats, ii) low-intensity swats, iii) multimodal calls
 (airborne calls and call ripples), and iv) multimodal calls alternating
 with high-intensity swats (Figure 1). Each stimulus was played back every
 2 seconds, which is consistent with the average natural call rate
 [37] and within the natural range of swat rates
 [19]. For a subset of the males (n = 15) we
 performed an additional trial at the end of the experiment, playing back
 the multimodal call stimulus once every four seconds (i.e. “slow
 multimodal call”, Figure 1) to control for the reduced call rate of the
 treatment in which the multimodal call alternated with a high-intensity
 swat ripple. For each frog (n = 29 frogs; # trials/frog:
 range = 1 to 5, median = 4; 106 trials total), we compared call rate
 (average # calls/sec) and complexity (average # chucks/whine) between
 control conditions (i.e., silent playback) and treatment playback. Males
 called during all silent control conditions (106/106 trials), but
 sometimes ceased calling (9/106 trials) or only produced a single call
 (2/106 trials) in response to a treatment playback. All 11 of these latter
 trials were excluded from call rate analysis, whereas only the 9 trials in
 which the male ceased calling were excluded from complexity analysis. We
 also excluded 2 treatment playbacks due to playback error or a sudden,
 loud stimulus from the environment. All acoustic analyses were performed
 in Adobe Audition CS6. 
 <em><strong>Bat
 foraging & female choice
 experiments</strong></em>
 The effectiveness and
 consequences of calling strategies are ultimately defined by the responses
 of the receivers. We therefore investigated how frog-biting midges impact
 decision-making in foraging bats and female túngara frogs by modulating
 the calling behaviours of male frogs and their rivals.
 Bats (n = 5; 10-20
 trials/bat per experiment) and female túngara frogs (n = 24; 1 trial/female per
 experiment) were presented with two-choice tests of airborne (no ripples)
 frog call playbacks to assess preferences (see Supplementary Materials for
 detailed descriptions of methods). 
 To evaluate relative
 preferences between a calling, swatting male and a rival responding to his
 swat ripples (i.e. the scenario examined in the male behavioural
 experiment), we broadcast calls of a male who intermittently swats – i.e.
 representative of the call rate and complexity of a frog that swats every
 2 seconds; 0.34 calls/second, 1.00 chucks/call [19]- versus a calling rival male responding to
 high-intensity swat ripples (i.e. representative of the call rate and
 complexity of frogs that were exposed to a high-intensity swat ripple once
 every 2 seconds; 0.5 calls/second, 1.75 chucks/call). In a second
 two-choice test, to investigate if and to what extent responding to swat
 ripples alters receiver preferences relative to a typical, non-swatting
 male, we broadcast calls of a characteristic non-swatting, calling male
 (i.e. representative of the call rate and complexity of a rival frog
 before being exposed to high-intensity swat ripples; 0.45 calls/second,
 1.00 chucks/call) and calling male responding to high-intensity swat
 ripples (same as in previously mentioned two-choice test). A third
 two-choice test was given to a single bat (n = 1; 20 trials), in which we
 broadcast calls of a male who intermittently swats, but does not append
 ornamental chucks (i.e. approximate call rate of a frog that swats every 2
 seconds, but without ornamental chucks; 0.34 calls/second, 0 chucks/call)
 versus a calling rival male responding to high-intensity swat ripples
 (same as above).
 <em><strong>Statistical
 analyses</strong></em>
 For our analyses, we
 formulated generalized linear mixed models fit under a Bayesian framework
 using the brms package version 2.14.4 [39] and R version 4.0.3 [40]. We used weakly informative priors to ensure
 that draws from the prior could be from any hypothetical dataset
 [41]. In this way, these priors include probability
 mass around potential, but not implausible extreme values. We ran 4 chains
 with 3000 iterations each and discarded the first 500, resulting in 10,000
 posterior samples. To ensure model convergence, we visually examined
 traceplots for good mixing of chains and confirmed that 
  &lt; 1.1 for all parameters. We
 performed posterior predictive checks to assess model fit with the
 bayesplot package version 1.8.1 [42]. Models were compared by assessing expected log
 pointwise predictive densities with the loo package [43]. See Table S3 for details specific to each
 model. Effects were determined using the hypothesis function in brms,
 first with two-side tests to determine an effect and directionality and
 subsequently a post-hoc one-sided test. Comparisons of effects between
 treatments were determined by subtracting the posterior probability
 densities from one another.  (See manuscript and supplementary materials for
 references, figures and tables.)
description: # Ripple effects in a communication network: anti-eavesdropper defence
 elicits elaborated sexual signals in rival males
 Authors: Brian C. Leavell,
 Hoover Pantoja-Sánchez, Viviana Vélez, Claire T. Hemingway, Kyle Wilhite,
 Wouter Halfwerk, Ximena E. Bernal Dates of data collection: 2017-2019
 Location of data collection: Gamboa, Panamá Keywords: communication,
 male-male competition, predator-prey, foraging, vibratory cue, sexual
 selection ## Audio Playback Files: Audio Playback Files: *
 “audio_call_airborne.wav” * “audio_call_ripple.wav” *
 “audio_swat_highintensity.wav” * “audio_swat_lowintensity.wav” ## Data
  (variable descriptions shown in Scripts section below):
 field_vibro_rec_data.csv * Output from “d_wave.m” MATLAB script when
 processing laser doppler vibrometer audio files recorded in the field *
 Measurements of call and swat ripples from the field * Variables * Note:
 “NA” indicates that there was no value, as the measurement category did
 not pertain to file’s “rippletype” * male = unique ID for individual male
 túngara frog * rippletype = denotes cause of ripple (i.e. call- or
 swat-induced) * File = audio file name of individual sample *
 flicking_appendage = which appendage(s) the frog swatted with to create
 ripple in associated sample * midge_count_on_frog = number of midges on
 frog at moment swat began * swat_count = number of swats that generated
 ripple in sample * frog_orientation_to_laser = which side of frog faced
 towards the point on water surface being measured by the laser * A =
 anterior * L = left side (frog’s perspective) * R = right side (frog’s
 perspective) * P = posterior * swat_orientation_to_laser =  indicates
 whether the swatting appendage(s) faced towards (i.e. near) or away from
 (i.e. far) the point on the water surface being measured by the laser *
 frog_orientation_to_laser_radians = conversion of frog orientation to
 laser into radians (not used in analyses) * vel_max_mm_per_s = maximum
 velocity (mm/sec) of sampled ripple * vel_rms = RMS velocity (mm/sec) of
 sampled ripple * domin_freq_vel = dominant frequency (Hz) of sampled
 ripple (derived from velocity) * v_energy = energy of sampled ripple
 (derived from velocity) * disp_app_mm = maximum displacement of water
 surface (mm, peak-to-peak) * disp_rms = RMS displacement of water surface
 (mm) * domin_freq_disp = dominant frequency (Hz) of sampled ripple
 (derived from displacement) * disp_energy = energy of sampled ripple
 (derived from displacement) experiment_calibrations.csv * Output from
 “d_wave.m” MATLAB script when processing laser doppler vibrometer audio
 files recorded during experiment calibrations * Measurements of call and
 swat ripple playbacks from experiment calibrations * Variables   * date =
 night of experiment (trials and calibrations that extended into the early
 AM were still assigned to previous date) * Audio.file = sequence of
 samples * file = individual audio sample * treatment = one of 3
 categories, low-intensity swat, high-intensity swat, or call rate.
 Threshold for "High" vs. "Low" categories of maximum
 velocity of swat ripple is based on the median estimate from in situ
 Bayesian GLMM (5.84 mm/s, 4.55-7.51 mm/s 95% CI). * speaker_LorR = 2
 playback stations were used in the experiment, one on each side of the
 frog, to control for potential side biases * pre_post = indicates whether
 calibration audio was recorded pre- or post-experiment * vel_max_mm_per_s
 = maximum velocity (mm/sec) of sampled ripple * vel_rms = RMS velocity
 (mm/sec) of sampled ripple * domin_freq_vel = dominant frequency (Hz) of
 sampled ripple (derived from velocity) * v_energy = energy of sampled
 ripple (derived from velocity) * disp_app_mm = maximum displacement of
 water surface (mm, peak-to-peak) * disp_rms = RMS displacement of water
 surface (mm) * domin_freq_disp = dominant frequency (Hz) of sampled ripple
 (derived from displacement) * disp_energy = energy of sampled ripple
 (derived from displacement) * Heirarchical structure =
 date/pre_post/speaker_LorR/treatment/Audio.file/file
 male_tungara_response_to_ripples.csv * Behavioral data from rival response
 experiment * Variables * Note: “NA” indicates that measurements were not
 made, either because there were no calls in the recording or if there was
 only 1 call in the recording and measurements that require at least 2
 calls to be made (e.g. “call rate”) were not possible. In the columns
 “Call [#]”, “NA” is used to fill remaining cells in the row after the
 final call of the sequence for that recording. * date = night of
 experiment * frog = unique ID for individual male túngara frog * treatment
 = playback used for trial * "hi swat" = high-intensity swat
 ripple played back once every 2 seconds (no airborne playback) * "lo
 swat" = low-intensity swat ripple played back once every 2 seconds
 (no airborne playback) * "call only" = call ripple played back
 with airborne playback of a call (whine + 1 chuck), played back once every
 2 seconds * "call and swat" = alternating call ripple (with
 airborne call; whine + 1 chuck) and high-intensity swat, once every 2
 seconds (i.e. second 0 = call ripple and airborne call, second 2 =
 high-intensity swat, second 4 = call ripple and airborne sound, second 6 =
 high-intensity swat, ...) * "call and muted swat" = same as
 "call and swat" treatment, but the swat playback was muted (i.e.
 did not play), thus this treatment featured a call ripple with airborne
 call (whine + 1 chuck) once every 4 seconds * side = left (L) or right (R)
 indicates which speaker was played back during trial; two speaker
 locations were used to control for the effect of side biases (see methods
 for further details) * order_of_playback = denotes the # in sequence of
 trials; treatments were randomized across trials, so order_of_playback can
 be used to determine effect of treatment position across trials on male
 response * original_audio = audio file number * min = minute of trial (1 =
 silent playback, 2 = treatment playback) * renumbered = randomized
 placeholder number assigned to file to ensure that the researcher
 analyzing the file was blind to the condition * calls = number of whines
 in 1 minute * time = duration (seconds) from start of 1st call to start of
 last call (within 1 minute) * mincallrate = call rate (calls/time) within
 minute portion of trial * mincomplexity = chuckstotal/calls;  average
 complexity per call within minute portion of trial * chuckstotal = total
 number of chucks appended to whines within 1 minute * First10seccallrate =
 call rate within first 10 seconds of minute * First10seccomplexity =
 average complexity per call within first 10 seconds of minute *
 Last10seccallrate = call rate within first 10 seconds of minute *
 Last10seccomplexity = average complexity per call within first 10 seconds
 of minute * Maxcomplexity = greatest # of chucks appended to a whine
 within 1 minute * Call [#] = these column heads refer to the order of
 whines (calls) produced by a frog within the given minute; the value for a
 given column indicates the number of chucks appended to that whine; e.g.
 for a given frog, if the value for column “Call 3” is “2”, this indicates
 that the 3rd whine produced by the frog in the given minute had 2 chucks
 appended mate_choice_experiment1.csv * Behavioral data from female choice
 experiment; swatter vs. rival responding to swat ripples * Variables *
 date: the date that a night of experiments began. (note: as these frogs
 are nocturnal, experiments began in the evening and would sometimes
 continue past midnight. in these cases, all experiments within the same
 night were assigned the date in which the night began.) * frog: unique ID
 of female túngara frog * swatter: the approximate call rate and complexity
 of a frog that swats every 2 seconds (i.e. 0.34 calls/second; 1.00
 chucks/call) see data from Leavell et al. (2022) Am. Nat. *
 neighbor_highswat: median call rate and complexity of frogs that were
 exposed to a high-intensity swat ripple once every 2 seconds (i.e., 0.5
 calls/second; 1.75 chucks/call) * latency: the duration from the start of
 the trial to (minutes.seconds; i.e. 1.22 = 1 minute, 22 seconds) * time:
 hour and minute in which trial took place. (hour.minute; i.e. 9.44 = 21:44
 or 9:44pm) mate_choice_experiment2.csv • Behavioral data from female
 choice experiment; male not responding to swat ripples vs. male responding
 to swat ripples bats.csv • Variables * date: the date that a night of
 experiments began. (note: as these frogs are nocturnal, experiments began
 in the evening and would sometimes continue past midnight. in these cases,
 all experiments within the same night were assigned the date in which the
 night began.) * frog: unique ID of female túngara frog (note: restarts
 numbering each night). * neighbor_control: the median call rate and
 complexity of the rival frog before being exposed to high-intensity swat
 ripples (i.e., 0.45 calls/second; 1.00 chucks/call) * neighbor_highswat:
 median call rate and complexity of frogs that were exposed to a
 high-intensity swat ripple once every 2 seconds (i.e., 0.5 calls/second;
 1.75 chucks/call) * latency: the duration from the start of the trial to
 (minutes.seconds; i.e. 1.22 = 1 minute, 22 seconds) * time: hour and
 minute in which trial took place. (hour.minute; i.e. 9.44 = 21:44 or
 9:44pm) * Behavioral data from bat foraging experiments *
 Variables * bat: unique ID of *Trachops cirrhosus* individual *
 experiment: two-choice tests * 1v1: not used for these analysis. same as
 1v2, but the swatter playback was 0.34 call/second, whine only (no chuck).
 * 1v2: same as "experiment 1" playback in mate_choice trials *
 i.   swatter: the approximate call rate and complexity of a frog that
 swats every 2 seconds (i.e. 0.34                     calls/second; 1.00
 chucks/call) see Leavell et al. (2022) Am. Nat. * ii.  neighbor_highswat:
 median call rate and complexity of frogs that were exposed to a
 high-intensity swat ripple once every 2 seconds (i.e., 0.5 calls/second;
 1.75 chucks/call) * 2: same as "experiment 2" playback in
 mate_choice trials * i.   neighbor_control: the median call rate and
 complexity of the rival frog before being exposed to high-intensity swat
 ripples (i.e., 0.45 calls/second; 1.00 chucks/call) * ii. 
 neighbor_highswat: median call rate and complexity of frogs that were
 exposed to a high-intensity swat ripple once every 2 seconds (i.e., 0.5
 calls/second; 1.75 chucks/call) * choice: which speaker was attacked by
 bat. 0 = simple (lower call rate and complexity); 1 = complex (greater
 call rate and complexity) * feeding: experiments were spread across a
 maximum of 3 feeding sessions per night. 1, 2, 3 = 1st, 2nd, and 3rd
 feeding sessions of the night. * date: the date that a night of
 experiments began. (note: experiments began in the evening and would
 sometimes continue past midnight. in these cases, all experiments within
 the same night were assigned the date in which the night began.) ##
 Scripts: 1_Ripple_analysis_insitu.Rmd * Script for analysis of field
 recordings * Requires “field_vibro_rec_data.csv”
 2_Ripple_analysis_experiment_calibrations.Rmd * Script for analysis of
 ripple calibration recordings * Requires “experiment_calibrations.csv”
 3_rival_males.Rmd * Script for analysis of behavioral data from rival
 response experiment * Requires “male_tungara_response_to_ripples.csv”
 4_mate_choice.Rmd * Script for analysis of behavioral data from female
 choice experiments * Requires “mate_choice_experiment1.csv” and
 “mate_choice_experiment2.csv” 5_bat_foraging.Rmd * Script for analysis of
 behavioral data from bat foraging experiments * Requires “bats.csv”
 6_audio_file_visualizations.Rmd * Visualizations of ripple and airborne
 stimuli used for playbacks; shown in Figure 1 of manuscript * Requires
 “audio_call_airborne.wav”, “audio_call_ripple.wav”,
 “audio_swat_highintensity.wav”, “audio_swat_lowintensity.wav” d_wave.m *
 Script for analysing field and calibration audio files recorded as output
 from laser doppler vibrometer ## Methods (from manuscript): *Rival male
 experiment* In August 2017, we collected calling male túngara frogs 1 to 4
 hours after sunset from breeding sites within 1.5 km of Smithsonian
 Tropical Research Institute facilities (Gamboa, Panamá; 9°07.0’N,
 79°41.9’W). Frogs took part in behavioural experiments in a large outdoor
 flight cage (5×5×2.5 m) within 3 hours following capture and before
 midnight. Following protocols established by the American Society of
 Ichthyologists and Herpetologists
 (), after each experiment
 we weighed, measured and toe-clipped the frog (to prevent testing the same
 individual multiple times), and released him the following night at his
 collection location. The research reported here complied with University
 of Texas at Austin #s AUP-2015-00048, AUP-2017-00051 and AUP-2020-00034;
 STRI IACUC protocols 2017-0102-2020-A8, 2018-0411-2021; and República de
 Panamá permits SE/AO-1-17, SE/A-44-18, SE/A-40-19, SE/A 69-15 and
 SE/AH-2-6. **Field recordings.** To sample the natural variation of swat
 and call ripples from calling male túngara frogs, we recorded ripples from
 six males (n = 2 in situ; n = 4 in a planter tray filled with water from
 the breeding site, placed by the original calling site). We measured the
 frequency, velocity and displacement of the water ripples with a digital
 laser vibrometer (LDV; Polytech PDV-100; Velocity = 20 mm/s, Low Pass = 22
 kHz, High Pass = none). The laser was focused on a reflective marker
 floating on the water surface; its reflection is detected by the LDV,
 allowing measurement of the surface vibrational velocities. We recorded
 these measurements from the digital output of the LDV using a Marantz
 audio recorder (48 kHz sample rate, 24 bit). See Supplementary Materials
 for a full description of the recording setup. We analysed call ripples
 (52 samples from 6 males; range: min = 5, max = 13 per male) and swat
 ripples (66 samples from 6 males; range: min = 5, max = 15 per male) using
 the velocity measurements recorded from the LDV digital output. We also
 converted velocity data to displacement values for comparison with related
 studies that have used this variable to characterize call ripples in this
 species (e.g. [32,36]). All ripple characterization analyses were
 performed in MATLAB R2016a () using
 custom code (Supplementary Materials). The vertical velocity of a swat
 ripple differed depending on the location of the sensor relative to the
 side of the body that swats (Figure S1, Supplementary Materials and R
 scripts for details of the analysis). We therefore tested calling
 behaviour in response to both high- and low-velocity swat ripples to
 determine male responses to the range of swat ripple intensities
 encountered in the wild. We used the point estimate of the median maximum
 velocity of all recorded swat ripples (5.84 mm/sec. peak-to-peak), which
 was between the 95% credible intervals for the median low- and
 high-intensity swat values, as a guide to calibrate low- and high-velocity
 swat playbacks. While there was variation across playbacks, the vast
 majority of calibration measurements were within the range measured from
 the field recordings (see Figures S2-3 and associated R scripts for
 further details). **Experimental setup.** For our ripple playback files,
 we used a total of three field recordings. These files represented the
 median dominant frequency and median maximum velocity of either a i)
 high-velocity swat, ii) low-velocity swat, or iii) call ripple. As
 playback of call ripples always co-occurred with an airborne call
 playback, we ensured that the call ripple accurately coincided with the
 airborne call component by synchronizing their playback to match the
 temporal profile of the field recording. For the airborne component of the
 multimodal call playback, we generated a call comprised of a whine with
 one chuck, as this is the most common call complexity observed in natural
 settings (see Supplementary Materials for details) [37,38]. Prior to an
 experiment, a male (n = 29 frogs; no males were from field recordings) was
 placed in a pool (2.6 × 2.1 m) of dechlorinated tap water. The male was
 contained within a ripple cage but could otherwise call freely. This
 ripple cage, used in a previous study of call-induced ripples, is
 acoustically transparent to low frequency ripples [33]. The cylindrical
 ripple cage (10.5 cm total diameter) consisted of a plastic, circular base
 and top held in place by three evenly spaced, vertical screws (~0.4 cm
 diam.). Monofilament fishing line (~0.36 mm thick) was strung vertically,
 encircling all sides of the plastic base and top (spaced ~0.25 cm apart
 creating an acoustically transparent cylinder 8 cm. in diameter) to
 prevent the frog from escaping. Once the male was consistently calling, he
 was presented with the first of four trials, which were presented in
 random order and separated by at least 1 minute of silence. The order of
 presentation did not affect male responses (Tables S1-2). Each trial
 consisted of a 1-minute silent control playback and 1-minute playback of
 one of the following treatments: i) high-intensity swats, ii)
 low-intensity swats, iii) multimodal calls (airborne calls and call
 ripples), and iv) multimodal calls alternating with high-intensity swats
 (Figure 1). Each stimulus was played back every 2 seconds, which is
 consistent with the average natural call rate [37] and within the natural
 range of swat rates [19]. For a subset of the males (n = 15) we performed
 an additional trial at the end of the experiment, playing back the
 multimodal call stimulus once every four seconds (i.e. “slow multimodal
 call”, Figure 1) to control for the reduced call rate of the treatment in
 which the multimodal call alternated with a high-intensity swat ripple.
 For each frog (n = 29 frogs; # trials/frog: range = 1 to 5, median = 4;
 106 trials total), we compared call rate (average # calls/sec) and
 complexity (average # chucks/whine) between control conditions (i.e.,
 silent playback) and treatment playback. Males called during all silent
 control conditions (106/106 trials), but sometimes ceased calling (9/106
 trials) or only produced a single call (2/106 trials) in response to a
 treatment playback. All 11 of these latter trials were excluded from call
 rate analysis, whereas only the 9 trials in which the male ceased calling
 were excluded from complexity analysis. We also excluded 2 treatment
 playbacks due to playback error or a sudden, loud stimulus from the
 environment. All acoustic analyses were performed in Adobe Audition CS6.
 *Bat foraging & female choice experiments* The effectiveness and
 consequences of calling strategies are ultimately defined by the responses
 of the receivers. We therefore investigated how frog-biting midges impact
 decision-making in foraging bats and female túngara frogs by modulating
 the calling behaviours of male frogs and their rivals. Bats (n = 5; 10-20
 trials/bat per experiment) and female túngara frogs (n = 24; 1
 trial/female per experiment) were presented with two-choice tests of
 airborne (no ripples) frog call playbacks to assess preferences (see
 Supplementary Materials for detailed descriptions of methods). To evaluate
 relative preferences between a calling, swatting male and a rival
 responding to his swat ripples (i.e. the scenario examined in the male
 behavioural experiment), we broadcast calls of a male who intermittently
 swats – i.e. representative of the call rate and complexity of a frog that
 swats every 2 seconds; 0.34 calls/second, 1.00 chucks/call [19] – versus a
 calling rival male responding to high-intensity swat ripples (i.e.
 representative of the call rate and complexity of frogs that were exposed
 to a high-intensity swat ripple once every 2 seconds; 0.5 calls/second,
 1.75 chucks/call). In a second two-choice test, to investigate if and to
 what extent responding to swat ripples alters receiver preferences
 relative to a typical, non-swatting male, we broadcast calls of a
 characteristic non-swatting, calling male (i.e. representative of the call
 rate and complexity of a rival frog before being exposed to high-intensity
 swat ripples; 0.45 calls/second, 1.00 chucks/call) and calling male
 responding to high-intensity swat ripples (same as in previously mentioned
 two-choice test). A third two-choice test was given to a single bat (n =
 1; 20 trials), in which we broadcast calls of a male who intermittently
 swats, but does not append ornamental chucks (i.e. approximate call rate
 of a frog that swats every 2 seconds, but without ornamental chucks; 0.34
 calls/second, 0 chucks/call) versus a calling rival male responding to
 high-intensity swat ripples (same as above). *Statistical analyses* For
 our analyses, we formulated generalized linear mixed models fit under a
 Bayesian framework using the brms package version 2.14.4 [39] and R
 version 4.0.3 [40]. We used weakly informative priors to ensure that draws
 from the prior could be from any hypothetical dataset [41]. In this way,
 these priors include probability mass around potential, but not
 implausible extreme values. We ran 4 chains with 3000 iterations each and
 discarded the first 500, resulting in 10,000 posterior samples. To ensure
 model convergence, we visually examined traceplots for good mixing of
 chains and confirmed that R ̂ &lt; 1.1 for all parameters. We performed
 posterior predictive checks to assess model fit with the bayesplot package
 version 1.8.1 [42]. Models were compared by assessing expected log
 pointwise predictive densities with the loo package [43]. See Table S3 for
 details specific to each model. Effects were determined using the
 hypothesis function in brms, first with two-side tests to determine an
 effect and directionality and subsequently a post-hoc one-sided test.
 Comparisons of effects between treatments were determined by subtracting
 the posterior probability densities from one another.