58
1 Introduction
The butterfl yfi shes (Family Chaetodontidae) are a conspicuous, speciose, and highly
social family of coral reef fi shes. The family includes four genera of coralfi shes
( Amphichaetodon , Chelmon , Chelmonops , Coradion ), four genera of bannerfi shes
( Forcipiger , Hemitaurichthys , Heniochus , Johnrandallia ), and a clade composed of
the genera Prognathodes and Chaetodon , the latter of which represents approximately 70 % of the species in the family (Blum 1988 ; Smith et al. 2003 ; Fessler and
Westneat 2007 ; Bellwood et al. 2010 ). The butterfl yfi shes are diverse in their feeding
habits and they include species that are planktivores, obligate and facultative corallivores, benthic invertebrate predators, and omnivores (reviewed by Cole and
Pratchett 2014 ). Individuals are rarely solitary and several types of social relationships are found among species (Hourigan 1989 ; Yabuta and Berumen 2014 ). Many
species form monogamous pairs that are maintained for several years (or for life) in
which the same two individuals carry out all of their daytime activities in close proximity to one another (separated by only a few body lengths) while foraging over large
home ranges, or defending a feeding territory (Reese 1975 ; Fricke 1986 ; Tricas 1989 ;
Roberts and Ormond 1992 ). Other species form long-term haremic associations that
consist of a single male and multiple females. During daylight hours some species
form larger groups, shoals, or schools that feed on plankton in the water column
above the reef. Their highly conspicuous species-specifi c color patterns and behavioral displays are used to visually mediate many social interactions such as the recognition of conspecifi cs (Zumpe 1965 ; Boyle and Tricas 2014 ), identifi cation of
mates (Reese 1975 ; Yabuta 2002 ), defense of territories (Tricas 1985 , 1989 ; Roberts
1992; Wrathall et al. 1992 ; Kosaki 1999 ), avoidance of predators (Motta 1984 ;
Neudecker 1989 ), and determination of behavioral state (Hamilton and Peterman
1971 ). However, the more recent discoveries of novel anatomical features associated
with the lateral line system and the discovery of sound production have refocused
attention on butterfl yfi sh bioacoustic behavior in relation to their behavioral ecology
and evolution, which is the focus of this chapter.
The laterophysic connection (LC; Figs. 1 and 2 ) is a unique anatomical feature
in the genus Chaetodon that is defi ned by the presence of cylindrical, anterior
swim bladder horns in proximity to a medial opening in the lateral line canal in the
supracleithral bone, located at the posterior margin of the skull. This unique feature was proposed to facilitate the transmission of sound pressure stimuli to the
lateral line canal system and to the ear (Webb 1998 ; Webb et al. 2006 ). Behavioral
studies in the lab and fi eld demonstrate that sound is produced in all Chaetodon
species and in representatives of other butterfl yfi sh genera studied thus far (summarized in Tricas and Boyle 2015a ). The tendency for Chaetodon species to form
monogamous pairs and other close social associations is consistent with their use
of both the auditory and lateral line systems for the perception of acoustic signals
at short distances. This may be especially important on coral reefs in which the
soundscape is characterized by high intensity, broadband, ambient noise levels that
T.C. Tricas and J.F. Webb
1 Introduction
The butterfl yfi shes (Family Chaetodontidae) are a conspicuous, speciose, and highly
social family of coral reef fi shes. The family includes four genera of coralfi shes
( Amphichaetodon , Chelmon , Chelmonops , Coradion ), four genera of bannerfi shes
( Forcipiger , Hemitaurichthys , Heniochus , Johnrandallia ), and a clade composed of
the genera Prognathodes and Chaetodon , the latter of which represents approximately 70 % of the species in the family (Blum 1988 ; Smith et al. 2003 ; Fessler and
Westneat 2007 ; Bellwood et al. 2010 ). The butterfl yfi shes are diverse in their feeding
habits and they include species that are planktivores, obligate and facultative corallivores, benthic invertebrate predators, and omnivores (reviewed by Cole and
Pratchett 2014 ). Individuals are rarely solitary and several types of social relationships are found among species (Hourigan 1989 ; Yabuta and Berumen 2014 ). Many
species form monogamous pairs that are maintained for several years (or for life) in
which the same two individuals carry out all of their daytime activities in close proximity to one another (separated by only a few body lengths) while foraging over large
home ranges, or defending a feeding territory (Reese 1975 ; Fricke 1986 ; Tricas 1989 ;
Roberts and Ormond 1992 ). Other species form long-term haremic associations that
consist of a single male and multiple females. During daylight hours some species
form larger groups, shoals, or schools that feed on plankton in the water column
above the reef. Their highly conspicuous species-specifi c color patterns and behavioral displays are used to visually mediate many social interactions such as the recognition of conspecifi cs (Zumpe 1965 ; Boyle and Tricas 2014 ), identifi cation of
mates (Reese 1975 ; Yabuta 2002 ), defense of territories (Tricas 1985 , 1989 ; Roberts
1992; Wrathall et al. 1992 ; Kosaki 1999 ), avoidance of predators (Motta 1984 ;
Neudecker 1989 ), and determination of behavioral state (Hamilton and Peterman
1971 ). However, the more recent discoveries of novel anatomical features associated
with the lateral line system and the discovery of sound production have refocused
attention on butterfl yfi sh bioacoustic behavior in relation to their behavioral ecology
and evolution, which is the focus of this chapter.
The laterophysic connection (LC; Figs. 1 and 2 ) is a unique anatomical feature
in the genus Chaetodon that is defi ned by the presence of cylindrical, anterior
swim bladder horns in proximity to a medial opening in the lateral line canal in the
supracleithral bone, located at the posterior margin of the skull. This unique feature was proposed to facilitate the transmission of sound pressure stimuli to the
lateral line canal system and to the ear (Webb 1998 ; Webb et al. 2006 ). Behavioral
studies in the lab and fi eld demonstrate that sound is produced in all Chaetodon
species and in representatives of other butterfl yfi sh genera studied thus far (summarized in Tricas and Boyle 2015a ). The tendency for Chaetodon species to form
monogamous pairs and other close social associations is consistent with their use
of both the auditory and lateral line systems for the perception of acoustic signals
at short distances. This may be especially important on coral reefs in which the
soundscape is characterized by high intensity, broadband, ambient noise levels that
T.C. Tricas and J.F. Webb