Communication Theories - Soundscape Ecology: Principles, Patterns, Methods and Applications - page 98

in the conducting xylem tissue of leaves, stems, and trunks. The sound represents
the vibration produced by the single-cell collapse caused by gradual dehydration
and prolonged water deficit. This acoustic emission is audible only in part; the
majority pertains to ultrasonic frequencies. It is commonly used by botanists to
measure such acoustic emissions to evaluate the level of drought stress in living
plants and more precisely to determine the threshold water potential at which the
water-conducting system initiates damage (Jackson and Grace 1996 ). This
approach can only determine the proportion of embolism in a conducting system
and is not able to determine the percentage of reduction in hydraulic conductivity.
Acoustic utilization seems more important than the amount of research could
speculate. In 1987 Mattson and Haack ( 1987 ) advanced the hypothesis that
drought-stressed trees could produce a cavitation sound audible to plant-eating
insects. It is not clear if the bark beetles are able to listen to the sounds produced
by trees, but in many insects the capacity to capture ultrasonic signals has been
found. For instance, the capacity of some butterflies and moths to escape the echoes
emitted by bats has been documented.
Summary
Communication is an important component of animal life, contributing to repro-
duction and to survival life traits. In communication there is a sender and a receiver
connected by an informative signal. A third subject is the eavesdropper or the
involuntary receiver that utilizes the information which circulates between a sender
and a receiver.
A communication theory represents a general framework used to describe the
plethora of observations, rules, and exceptions described in the variegated context
of animal communication.
Communication is costly in term of energy budget allocated by vocal
individuals, and a well-designed communicative framework should be the result
of a selective pressure.
Signal generation and emission is the first step of the communication process,
followed by other important steps/constraints such as transmission through the
medium, signal reception and processing, and finally the decisions based on the
perceived signal.
In the communication process the indirect intercept of a message/signal directed
to others is called eavesdropping, and this process represent an important evolu-
tionary phenomenon.
Echolocation, so common in bats, is a mechanism by which a communicative
channel is entirely used to evaluate the consistency and distance of a physical
context and potential prey and predators.
Heterospecific attraction may be defined as the capacity by a species to copy the
information shared by other species in the same location. For instance, resident
species can offer important information to transient species in terms of refuges or
foraging opportunities. Conspecific attraction remains a fundamental mechanism
that guides in territory selection.