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Bernal XE, Page RA. Tactics of evasion: strategies used by signallers to deter eavesdropping enemies from exploiting communication systems. Biol Rev Camb Philos Soc 2023; 98:222-242. [PMID: 36176190 DOI: 10.1111/brv.12904] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 09/03/2022] [Accepted: 09/06/2022] [Indexed: 01/12/2023]
Abstract
Eavesdropping predators, parasites and parasitoids exploit signals emitted by their prey and hosts for detection, assessment, localization and attack, and in the process impose strong selective pressures on the communication systems of the organisms they exploit. Signallers have evolved numerous anti-eavesdropper strategies to mitigate the trade-off between the costs imposed from signal exploitation and the need for conspecific communication. Eavesdropper strategies fall along a continuum from opportunistic to highly specialized, and the tightness of the eavesdropper-signaller relationship results in differential pressures on communication systems. A wide variety of anti-eavesdropper strategies mitigate the trade-off between eavesdropper exploitation and conspecific communication. Antagonistic selection from eavesdroppers can result in diverse outcomes including modulation of signalling displays, signal structure, and evolutionary loss or gain of a signal from a population. These strategies often result in reduced signal conspicuousness and in decreased signal ornamentation. Eavesdropping enemies, however, can also promote signal ornamentation. While less common, this alternative outcome offers a unique opportunity to dissect the factors that may lead to different evolutionary pathways. In addition, contrary to traditional assumptions, no sensory modality is completely 'safe' as eavesdroppers are ubiquitous and have a broad array of sensory filters that allow opportunity for signal exploitation. We discuss how anthropogenic change affects interactions between eavesdropping enemies and their victims as it rapidly modifies signalling environments and community composition. Drawing on diverse research from a range of taxa and sensory modalities, we synthesize current knowledge on anti-eavesdropper strategies, discuss challenges in this field and highlight fruitful new directions for future research. Ultimately, this review offers a conceptual framework to understand the diverse strategies used by signallers to communicate under the pressure imposed by their eavesdropping enemies.
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Affiliation(s)
- Ximena E Bernal
- Department of Biological Sciences, Purdue University, 915 W State Street, West Lafayette, IN, 47907, USA.,Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Republic of Panama
| | - Rachel A Page
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancón, Republic of Panama
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2
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Sedlock JL, Gomes DGE, Rubin JJ, Woody S, Hadi BAR, Barber JR. A phantom ultrasonic insect chorus repels low‐flying bats, but most are undeterred. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Dylan G. E. Gomes
- Department of Biological Sciences Boise State University Boise ID USA
- Cooperative Institute for Marine Resources Studies Hatfield Marine Science CenterOregon State University Newport OR USA
| | - Juliette J. Rubin
- Department of Biological Sciences Boise State University Boise ID USA
| | - Sarah Woody
- Biology Department Lawrence University Appleton WI USA
| | - Buyung A. R. Hadi
- Sustainable Impact Platform International Rice Research Institute Los Baños Philippines
| | - Jesse R. Barber
- Department of Biological Sciences Boise State University Boise ID USA
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3
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Prakash H, Greif S, Yovel Y, Balakrishnan R. Acoustically eavesdropping bat predators take longer to capture katydid prey signalling in aggregation. J Exp Biol 2021; 224:268371. [PMID: 34047777 DOI: 10.1242/jeb.233262] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 04/21/2021] [Indexed: 11/20/2022]
Abstract
Prey that are signalling in aggregation become more conspicuous with increasing numbers and tend to attract more predators. Such grouping may, however, benefit prey by lowering the risk of being captured because of the predator's difficulty in targeting individuals. Previous studies have investigated anti-predatory benefits of prey aggregation using visual predators, but it is unclear whether such benefits are gained in an auditory context. We investigated whether katydids of the genus Mecopoda gain protection from their acoustically eavesdropping bat predator Megaderma spasma when calling in aggregation. In a choice experiment, bats approached calls of prey aggregations more often than those of prey calling alone, indicating that prey calling in aggregation are at higher risk. In prey capture tasks, however, the average time taken and the number of flight passes made by bats before capturing a katydid were significantly higher for prey calling in aggregation than when calling alone, indicating that prey face lower predation risk when calling in aggregation. Another common anti-predatory strategy, calling from within vegetation, increased the time taken by bats to capture katydids calling alone but did not increase the time taken to capture prey calling from aggregations. The increased time taken to capture prey calling in aggregation compared with solitary calling prey offers an escape opportunity, thus providing prey that signal acoustically in aggregations with anti-predatory benefits. For bats, greater detectability of calling prey aggregations is offset by lower foraging efficiency, and this trade-off may shape predator foraging strategies in natural environments.
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Affiliation(s)
- Harish Prakash
- Centre for Ecological Sciences, Indian Institute of Science, Bangalore 560012, India
| | - Stefan Greif
- School of Zoology, Faculty of Life Sciences, Tel-Aviv University, Tel Aviv 69978, Israel.,Sagol School of Neuroscience, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Yossi Yovel
- School of Zoology, Faculty of Life Sciences, Tel-Aviv University, Tel Aviv 69978, Israel.,Sagol School of Neuroscience, Tel-Aviv University, Tel Aviv 69978, Israel
| | - Rohini Balakrishnan
- Centre for Ecological Sciences, Indian Institute of Science, Bangalore 560012, India
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4
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Neurophysiology goes wild: from exploring sensory coding in sound proof rooms to natural environments. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2021; 207:303-319. [PMID: 33835199 PMCID: PMC8079291 DOI: 10.1007/s00359-021-01482-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Revised: 03/21/2021] [Accepted: 03/23/2021] [Indexed: 10/27/2022]
Abstract
To perform adaptive behaviours, animals have to establish a representation of the physical "outside" world. How these representations are created by sensory systems is a central issue in sensory physiology. This review addresses the history of experimental approaches toward ideas about sensory coding, using the relatively simple auditory system of acoustic insects. I will discuss the empirical evidence in support of Barlow's "efficient coding hypothesis", which argues that the coding properties of neurons undergo specific adaptations that allow insects to detect biologically important acoustic stimuli. This hypothesis opposes the view that the sensory systems of receivers are biased as a result of their phylogeny, which finally determine whether a sound stimulus elicits a behavioural response. Acoustic signals are often transmitted over considerable distances in complex physical environments with high noise levels, resulting in degradation of the temporal pattern of stimuli, unpredictable attenuation, reduced signal-to-noise levels, and degradation of cues used for sound localisation. Thus, a more naturalistic view of sensory coding must be taken, since the signals as broadcast by signallers are rarely equivalent to the effective stimuli encoded by the sensory system of receivers. The consequences of the environmental conditions for sensory coding are discussed.
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Symes LB, Martinson SJ, Kernan CE, Ter Hofstede HM. Sheep in wolves' clothing: prey rely on proactive defences when predator and non-predator cues are similar. Proc Biol Sci 2020; 287:20201212. [PMID: 32842929 DOI: 10.1098/rspb.2020.1212] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Predation produces intense selection and a diversity of defences. Reactive defences are triggered by predator cues, whereas proactive defences are always in effect. We assess whether prey rely on proactive defences when predator cues do not correlate well with predation risk. Many bats use echolocation to hunt insects, and many insects have evolved to hear bats. However, in species-rich environments like Neotropical forests, bats have extremely diverse foraging strategies, and the presence of echolocation corresponds only weakly to the presence of predators. We assess whether katydids that live in habitats with many non-dangerous bat species stop calling when exposed to echolocation. For 11 species of katydids, we quantified behavioural and neural responses to predator cues, and katydid signalling activity over 24 h periods. Despite having the sensory capacity to detect predators, many Neotropical forest katydids continued calling in the presence of predator cues, displaying proactive defences instead (short, infrequent calls totalling less than 2 cumulative seconds of sound per 24 h). Neotropical katydid signalling illustrates a fascinating case where trophic interactions are probably mediated by a third group: bats with alternative foraging strategies (e.g. frugivory). Although these co-occurring bats are not trophically connected, their mere presence disrupts the correlation between cue and predation risk.
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Affiliation(s)
- Laurel B Symes
- Center for Conservation Bioacoustics, Cornell Lab of Ornithology, 159 Sapsucker Woods, Ithaca, NY 14850, USA.,Department of Biological Sciences, Dartmouth College, 78 College Street, Hanover, NH 03755, USA.,Smithsonian Tropical Research Institute, Balboa, Ancón, Panama City, Republic of Panama
| | - Sharon J Martinson
- Department of Biological Sciences, Dartmouth College, 78 College Street, Hanover, NH 03755, USA.,Smithsonian Tropical Research Institute, Balboa, Ancón, Panama City, Republic of Panama
| | - Ciara E Kernan
- Department of Biological Sciences, Dartmouth College, 78 College Street, Hanover, NH 03755, USA.,Smithsonian Tropical Research Institute, Balboa, Ancón, Panama City, Republic of Panama
| | - Hannah M Ter Hofstede
- Department of Biological Sciences, Dartmouth College, 78 College Street, Hanover, NH 03755, USA.,Smithsonian Tropical Research Institute, Balboa, Ancón, Panama City, Republic of Panama
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6
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Römer H. Directional hearing in insects: biophysical, physiological and ecological challenges. ACTA ACUST UNITED AC 2020; 223:223/14/jeb203224. [PMID: 32737067 DOI: 10.1242/jeb.203224] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Sound localisation is a fundamental attribute of the way that animals perceive their external world. It enables them to locate mates or prey, determine the direction from which a predator is approaching and initiate adaptive behaviours. Evidence from different biological disciplines that has accumulated over the last two decades indicates how small insects with body sizes much smaller than the wavelength of the sound of interest achieve a localisation performance that is similar to that of mammals. This Review starts by describing the distinction between tympanal ears (as in grasshoppers, crickets, cicadas, moths or mantids) and flagellar ears (specifically antennae in mosquitoes and fruit flies). The challenges faced by insects when receiving directional cues differ depending on whether they have tympanal or flagellar years, because the latter respond to the particle velocity component (a vector quantity) of the sound field, whereas the former respond to the pressure component (a scalar quantity). Insects have evolved sophisticated biophysical solutions to meet these challenges, which provide binaural cues for directional hearing. The physiological challenge is to reliably encode these cues in the neuronal activity of the afferent auditory system, a non-trivial problem in particular for those insect systems composed of only few nerve cells which exhibit a considerable amount of intrinsic and extrinsic response variability. To provide an integrative view of directional hearing, I complement the description of these biophysical and physiological solutions by presenting findings on localisation in real-world situations, including evidence for localisation in the vertical plane.
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Affiliation(s)
- Heiner Römer
- Institute of Biology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
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7
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Gone with the wind: Is signal timing in a neotropical katydid an adaptive response to variation in wind-induced vibratory noise? Behav Ecol Sociobiol 2020. [DOI: 10.1007/s00265-020-02842-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Abstract
Wind, a major source of environmental noise, forces invertebrates that communicate with plant-borne vibrations to adjust their signaling when communicating in windy conditions. However, the strategies that animals use to reduce the impact of wind noise on communication are not well studied. We investigated the effects of wind on the production of tremulatory signals in the neotropical katydid Copiphora brevirostris. First, we recorded katydid signaling activity and natural wind variation in the field. Additionally, we exposed katydid couples during their most active signaling time period to artificial wind of different levels, and we recorded the number of tremulations produced by the males. We found that wind levels are at their lowest between 2:00 and 5:00 in the morning, which coincides with peak signaling period for male katydids. Furthermore, we found that males produce significantly fewer tremulations when exposed to wind rather than acoustic noise or silence. Wind velocity significantly affected the number of tremulations produced during the wind treatment, with fewer tremulations produced with higher wind velocities. Our results show that katydids can time their vibratory signaling both in the short- and long-term to favorable sensory conditions, either through behavioral flexibility in response to short-term fluctuations in wind or as a result of an evolutionary process in response to predictable periods of low-wind conditions.
Significance statement
Animal communication can be hampered by noise across all sensory modalities. Most research on the effects of noise and the strategies to cope with it has focused on animals that use airborne sounds to communicate. However, although hundreds of thousands of invertebrates communicate with vibrational signals, we know very little about how noise affects this form of communication. For animals that rely on substrate-borne vibrations, wind represents the major source of environmental noise. Wind velocity levels can be predictable at a long-term scale (hours) but rather unpredictable at a short time scale (seconds). Both scales of variation are important for communication. Using a combination of field observations and lab experiments, we investigated the strategies used by a neotropical katydid Copiphora brevirostris to cope with vibrational noise induced by wind. Our results demonstrate that C. brevirostris times its signals at the long- and short-term range. Katydids signaled more at the times at night when wind velocity was lowest. Moreover, when exposed to wind gusts during their peak time of activity, katydids signaled more during the wind-free gaps.
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Geipel I, Kernan CE, Litterer AS, Carter GG, Page RA, Ter Hofstede HM. Predation risks of signalling and searching: bats prefer moving katydids. Biol Lett 2020; 16:20190837. [PMID: 32315594 DOI: 10.1098/rsbl.2019.0837] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Males signalling their attractiveness to females are at risk from predators that exploit mating signals to detect and locate prey. Signalling, however, is not the only risky activity in sexual interactions: mate searching can incur risk as well. Male Neotropical pseudophylline katydids produce both acoustic and vibrational signals (tremulations). Females reply to male signals with tremulations of their own, and both sexes walk to find one another. We asked if movement increases predation risk, and whether tremulation or walking was more attractive to predators. We offered the Neotropical gleaning bat Micronycteris microtis a series of two-choice tests, presenting the bats with katydid models that were motionless or moved in a way to mimic either tremulating or walking. We found that prey movements do put prey at risk. Although M. microtis can detect motionless prey on leaves, they preferred moving prey. Our study shows that movement can put searching or signalling prey in danger, potentially explaining why silent female katydids are frequently consumed by gleaning bats.
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Affiliation(s)
- Inga Geipel
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Panama
| | - Ciara E Kernan
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Panama.,Department of Biological Sciences, Dartmouth College, 78 College Street, Hanover, NH 03755, USA
| | - Amber S Litterer
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Panama.,Department of Biological Sciences, Dartmouth College, 78 College Street, Hanover, NH 03755, USA
| | - Gerald G Carter
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Panama.,Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH, USA
| | - Rachel A Page
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Panama
| | - Hannah M Ter Hofstede
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Panama.,Department of Biological Sciences, Dartmouth College, 78 College Street, Hanover, NH 03755, USA
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9
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Römer H. Insect acoustic communication: The role of transmission channel and the sensory system and brain of receivers. Funct Ecol 2019. [DOI: 10.1111/1365-2435.13321] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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10
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Symes LB, Martinson SJ, Hoeger LO, Page RA, ter Hofstede HM. From Understory to Canopy: In situ Behavior of Neotropical Forest Katydids in Response to Bat Echolocation Calls. Front Ecol Evol 2018. [DOI: 10.3389/fevo.2018.00227] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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11
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Hebets EA, Anderson A. Using cross-disciplinary knowledge to facilitate advancements in animal communication and science communication research. J Exp Biol 2018; 221:221/18/jeb179978. [DOI: 10.1242/jeb.179978] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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12
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Tiwari C, Diwakar S. Singers in the grass: call description of conehead katydids (family: Tettigoniidae) and observations on avoidance of acoustic overlap. BIOACOUSTICS 2018. [DOI: 10.1080/09524622.2018.1499553] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- Chandranshu Tiwari
- Department of Environmental Studies, University of Delhi, New Delhi, India
| | - Swati Diwakar
- Department of Environmental Studies, University of Delhi, New Delhi, India
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13
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Penna M, Cisternas J, Toloza J. Restricted responsiveness to noise interference in two anurans from the southern temperate forest. Ethology 2017. [DOI: 10.1111/eth.12644] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mario Penna
- Programa de Fisiología y Biofísica; Facultad de Medicina; Instituto de Ciencias Biomédicas; Universidad de Chile; Santiago Chile
| | - Javiera Cisternas
- Programa de Fisiología y Biofísica; Facultad de Medicina; Instituto de Ciencias Biomédicas; Universidad de Chile; Santiago Chile
| | - Jessica Toloza
- Programa de Fisiología y Biofísica; Facultad de Medicina; Instituto de Ciencias Biomédicas; Universidad de Chile; Santiago Chile
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