Bioacoustics Theories - Soundscape Ecology: Principles, Patterns, Methods and Applications - page 42

Chapter 3
Bioacoustics Theories
The structure and complexity of biophonies are the result of evolutionary pressure.
Physical structure of the organisms, adaptive mechanisms in sound production and
transmission, reduction of acoustic competition, and behavioral processes are
possible integrative strategies to enhance sonic context. Four major hypotheses
are considered relevant in the perceiving and communicating processes common to
all animal species: the morphological adaptation hypothesis (MAH), acoustic
adaptation hypothesis (AAH), acoustic niche hypothesis (ANH), and species rec-
ognition hypothesis (SRH).
The morphological adaptation hypothesis (MAH) refers to the role of body size
as a biological constraint of the vocalization organs and their acoustic performance,
confirming an inverse relationship between acoustic frequencies and body size.
The acoustic adaptation hypothesis (AAH) states that the environment is an
important cause of modification and alteration of acoustic signals. Dominant
frequencies and other long-distance calls are the result of an interaction between
the animals and the environment to maximize the efficiency of the emitted sounds.
Frequency and structure of acoustic repertoire are the plastic traits that can be
modified according to the environmental constraint.
The acoustic niche hypothesis (ANH) states that every species has a unique
acoustic space in which to structure the sonic species-specific signature to reduce
interspecific competition and to optimize intraspecific communication mechanisms.
The species recognition hypothesis (SRH) supposes that species living in sym-
patry try to reduce the risk of utilizing similar sonic traits that could confound
species in reproduction and create the risk of hybridization. This set of hypotheses
has epistemic relationships to form a meta-bioacoustic theory.