The production of communication signals at the air-water and water-substrate boundaries.

The 2 interfaces of the aquatic environment, the boundary between air-water and water-substrate, have distinctive physical characteristics that facilitate the production of communication signals. Recent evidence suggests that animals living on or near these boundaries use the interface to generate signals in 2 ways: (a) by producing a signal that propagates along the interface or (b) by producing a signal at the interface that is transmitted and detected within 1 of the component media. By examining the diversity of behaviors used to produce signals at these boundaries, the authors illustrate how human perception of these environments may cause researchers to incorrectly assume the environmental context of signal-generating behaviors and overlook modalities of communication pertinent to the animal.