vidual’s drainage tile, with sound amplitude at a maximum level directly
behind a nest. Observations of acoustic courtship in midshipman showed
that females are immediately directed to the nest entrance (a broken
cement block on a sandy substrate) by a humming male that is perched at
an artificial nest’s entrance with his head oriented to the front of the nest
(Brantley and Bass 1994). Additional phonotaxis experiments also demonstrated that females directly approach the front of a speaker, where sound
pressure is greatest (McKibben and Bass 1998). Together, these studies
point to the need for more analyses of sound fields and acoustic-related
behaviors in more complex, naturalistic habitats.
13. Complementary Explanations for Low-Frequency
Acoustic Signaling in Teleosts
A number of complementary explanations at different levels of analysis
may be put forth to explain the existence of low-frequency signaling in an
underwater environment (Fig. 2.13). Because of the greater diversity of
mechanistic information available for teleost fishes, this portion of our essay
focuses on their acoustic signals, thereby providing an example of a pluralistic approach to explaining existing vocal phenotypes. We have adopted
this research strategy to explain the existence of vocalizations and mate
choice among midshipman fish (Bass 1998; Bass et al. 1999). Here, we focus
mainly on mechanistic explanations that identify linkages between the ecological environment and behavioral or structural (e.g., neural, endocrine,
genetic) characters. Mechanisms are categorized as either behavioral–
ecological, behavioral–structural, or ecological–structural. There are also
fitness explanations that identify the consequences of mechanisms in terms
of survival or reproductive success and historical explanations that provide
adaptive interpretations for patterns observed over an individual’s lifetime
or geological time (see Bass 1998).
13.1. Behavioral–Ecological Mechanisms
The physical acoustics of signal propagation predicts that teleosts in very
shallow water habitats should utilize vocal signals with high-frequency
content, and yet the opposite appears to be the case for most species studied
so far. Why? One behavioral–ecological explanation is that low-frequency
calling behaviors lead to short communication distances in shallow water
habitats because of the severe influence of water depth on the range of
signal transmission. Short communication distances, in turn, may guard
against detection by competitors or predators (Forrest et al. 1993).The short
communication distances associated with low-frequency signals might also
reduce the negative impact that reflections and reverberations at the
2. Physical Acoustics of Underwater Sound Communication
53
behind a nest. Observations of acoustic courtship in midshipman showed
that females are immediately directed to the nest entrance (a broken
cement block on a sandy substrate) by a humming male that is perched at
an artificial nest’s entrance with his head oriented to the front of the nest
(Brantley and Bass 1994). Additional phonotaxis experiments also demonstrated that females directly approach the front of a speaker, where sound
pressure is greatest (McKibben and Bass 1998). Together, these studies
point to the need for more analyses of sound fields and acoustic-related
behaviors in more complex, naturalistic habitats.
13. Complementary Explanations for Low-Frequency
Acoustic Signaling in Teleosts
A number of complementary explanations at different levels of analysis
may be put forth to explain the existence of low-frequency signaling in an
underwater environment (Fig. 2.13). Because of the greater diversity of
mechanistic information available for teleost fishes, this portion of our essay
focuses on their acoustic signals, thereby providing an example of a pluralistic approach to explaining existing vocal phenotypes. We have adopted
this research strategy to explain the existence of vocalizations and mate
choice among midshipman fish (Bass 1998; Bass et al. 1999). Here, we focus
mainly on mechanistic explanations that identify linkages between the ecological environment and behavioral or structural (e.g., neural, endocrine,
genetic) characters. Mechanisms are categorized as either behavioral–
ecological, behavioral–structural, or ecological–structural. There are also
fitness explanations that identify the consequences of mechanisms in terms
of survival or reproductive success and historical explanations that provide
adaptive interpretations for patterns observed over an individual’s lifetime
or geological time (see Bass 1998).
13.1. Behavioral–Ecological Mechanisms
The physical acoustics of signal propagation predicts that teleosts in very
shallow water habitats should utilize vocal signals with high-frequency
content, and yet the opposite appears to be the case for most species studied
so far. Why? One behavioral–ecological explanation is that low-frequency
calling behaviors lead to short communication distances in shallow water
habitats because of the severe influence of water depth on the range of
signal transmission. Short communication distances, in turn, may guard
against detection by competitors or predators (Forrest et al. 1993).The short
communication distances associated with low-frequency signals might also
reduce the negative impact that reflections and reverberations at the
2. Physical Acoustics of Underwater Sound Communication
53