83
for other fi shes (Ladich and Fine 2006 ; Amorim 2006 ). For instance, the low frequency (9–69 Hz) aggressive tail slap and body pulse (137–184 Hz) sounds produced by C. multicinctus during social interactions increase in intensity with body
size (Tricas and Boyle 2015a ), and a similar relationship between sound intensity
and body size was reported for the head bob sound in F. fl avissimus (Boyle and Tricas
2011 ). A preliminary independent contrast analysis of the continuous variables that
defi ne sound characteristics (duration, peak frequency, median frequency, bandwidth, and intensity) produced by the tail slap in Chaetodon and other sound types in
Forcipiger shows evidence for correlated changes between sound duration and sound
pressure intensity (Tricas and Boyle 2015a ). This indicates a possible evolutionary
trend for the generation of loud and long pulse sounds by butterfl yfi shes, although
data on additional species are needed. Members of both Forcipiger and Chaetodon
engage in contests over territories to protect mates and food resources, so signals that
convey information on body size may reduce the risk of injury (e.g., lacerations, lost
scales, broken spines) that commonly occur during escalated disputes. Reinforcement
of information on relative body size conveyed by visual and acoustic signals may
also be used to maintain low levels of aggression, as commonly seen among neighbors in stable territories (Hourigan 1989 ; Tricas 1989 ; Roberts and Ormond 1992 ).
In C. multicinctus , acoustic information that is correlated with body size may also
benefi t individuals because body size is correlated with the size of a feeding territory
(Tricas 1989 ). Thus, sounds and other sensory cues may be important indicators of
resource-holding potential and be factors in the evolution of their social behavior.
In summary, sound production between mates and between conspecifi c competitors is common in Chaetodon and appears to be widespread among butterfl yfi shes.
Single pulse or pulse train sounds are produced during non-aggressive interactions
with mates, initial social interactions with unfamiliar conspecifi cs, aggressive interactions with competitors and during courtship. Several species produce multiple
sound types with a frequency range from infrasound to >1 kHz. Analysis of kinematics correlated with sound production indicates that sound production mechanisms
vary substantially among chaetodontid taxa. These sounds are likely to provide useful information about size or quality of the individual and have critical implications
for butterfl yfi sh ecology and fi tness. Additional kinematic and electromyographic
analyses of sound production in other butterfl yfi sh genera (e.g., Amphichaetodon ,
Coradion and Chelmon ) and angelfi shes (family Pomacanthidae, a hypothesized sister group to Chaetodontidae) are needed to more completely address the origin and
evolutionary diversifi cation of sound production in butterfl yfi shes.
6 The Acoustic Soundscape of Coral Reefs and Implications
for Butterfl yfi sh Acoustic Communication
Ambient acoustic noise is common in both freshwater and marine habitats and can
decrease the ability to detect biologically relevant sounds especially in taxa that
possess anatomical specializations for enhancement of hearing sensitivity and frequency range (see review by Ladich 2013 ). The coral reef environment is replete
Acoustic Communication in Butterfl yfi shes…
for other fi shes (Ladich and Fine 2006 ; Amorim 2006 ). For instance, the low frequency (9–69 Hz) aggressive tail slap and body pulse (137–184 Hz) sounds produced by C. multicinctus during social interactions increase in intensity with body
size (Tricas and Boyle 2015a ), and a similar relationship between sound intensity
and body size was reported for the head bob sound in F. fl avissimus (Boyle and Tricas
2011 ). A preliminary independent contrast analysis of the continuous variables that
defi ne sound characteristics (duration, peak frequency, median frequency, bandwidth, and intensity) produced by the tail slap in Chaetodon and other sound types in
Forcipiger shows evidence for correlated changes between sound duration and sound
pressure intensity (Tricas and Boyle 2015a ). This indicates a possible evolutionary
trend for the generation of loud and long pulse sounds by butterfl yfi shes, although
data on additional species are needed. Members of both Forcipiger and Chaetodon
engage in contests over territories to protect mates and food resources, so signals that
convey information on body size may reduce the risk of injury (e.g., lacerations, lost
scales, broken spines) that commonly occur during escalated disputes. Reinforcement
of information on relative body size conveyed by visual and acoustic signals may
also be used to maintain low levels of aggression, as commonly seen among neighbors in stable territories (Hourigan 1989 ; Tricas 1989 ; Roberts and Ormond 1992 ).
In C. multicinctus , acoustic information that is correlated with body size may also
benefi t individuals because body size is correlated with the size of a feeding territory
(Tricas 1989 ). Thus, sounds and other sensory cues may be important indicators of
resource-holding potential and be factors in the evolution of their social behavior.
In summary, sound production between mates and between conspecifi c competitors is common in Chaetodon and appears to be widespread among butterfl yfi shes.
Single pulse or pulse train sounds are produced during non-aggressive interactions
with mates, initial social interactions with unfamiliar conspecifi cs, aggressive interactions with competitors and during courtship. Several species produce multiple
sound types with a frequency range from infrasound to >1 kHz. Analysis of kinematics correlated with sound production indicates that sound production mechanisms
vary substantially among chaetodontid taxa. These sounds are likely to provide useful information about size or quality of the individual and have critical implications
for butterfl yfi sh ecology and fi tness. Additional kinematic and electromyographic
analyses of sound production in other butterfl yfi sh genera (e.g., Amphichaetodon ,
Coradion and Chelmon ) and angelfi shes (family Pomacanthidae, a hypothesized sister group to Chaetodontidae) are needed to more completely address the origin and
evolutionary diversifi cation of sound production in butterfl yfi shes.
6 The Acoustic Soundscape of Coral Reefs and Implications
for Butterfl yfi sh Acoustic Communication
Ambient acoustic noise is common in both freshwater and marine habitats and can
decrease the ability to detect biologically relevant sounds especially in taxa that
possess anatomical specializations for enhancement of hearing sensitivity and frequency range (see review by Ladich 2013 ). The coral reef environment is replete
Acoustic Communication in Butterfl yfi shes…