11.2 Ecological Constraints for Sound
Communication: From Grasshoppers to
Elephants
Heiner Romer
Institut fiir Zoologie, Karl-Franzens-Universitat, 8010 Graz, Austria
Abstract
Sensory ecology is mainly concerned with the mechanisms that enable an animal to
produce or utilize signals within its specific environment, and how the information
about identity or location of the sender is transmitted to the receiver(s). Biotic and
abiotic factors constrain the transmission of an acoustic signal and the performance
of receivers in detection and location. Since animals use acoustic signals in a wide
range of carrier frequencies - from infrasound to high ultrasound - with
corresponding wavelengths spanning a range from tens of meters to a few
millimeters, the rate of attenuation and degradation of sound signals varies largely
in different communication systems. As a result, the active range of a sound signal
covers probably hundreds of kilometers for marine mammals, several kilometers
for elephants, to less than 1 m in some grasshoppers. This chapter examines some
mechanisms by which these different animals achieve a maximum range of
communication. In particular, I will show how sound interference in stratified
environments can dramatically influence communication distance, and how
animals adapt their timing and location of the site of their signaling to these
environmental conditions.
Key words Thermal gradients, sound transmission, active space
1 Introduction
This chapter focuses on one limited aspect of acoustic communication, by
assuming that selection drives signals and signaling behavior towards greater range
and conspicuousness. The assumption, however, that acoustic signals of all species
should have design features to maximize the range of communication is not
correct. Communication between mates or parents and their young often ocurrs
over short ranges, and natural selection may favor a range of the signal over the
minimal distance necessary. Similar arguments hold for acoustic signals involved
in maintaining territories (review in Wiley and Richards 1982). Certainly, a
conspicuous signal may be advantageous, for example in mate attraction, but it
may also have costs. For example, predators and parasitoids are known to home in
Communication: From Grasshoppers to
Elephants
Heiner Romer
Institut fiir Zoologie, Karl-Franzens-Universitat, 8010 Graz, Austria
Abstract
Sensory ecology is mainly concerned with the mechanisms that enable an animal to
produce or utilize signals within its specific environment, and how the information
about identity or location of the sender is transmitted to the receiver(s). Biotic and
abiotic factors constrain the transmission of an acoustic signal and the performance
of receivers in detection and location. Since animals use acoustic signals in a wide
range of carrier frequencies - from infrasound to high ultrasound - with
corresponding wavelengths spanning a range from tens of meters to a few
millimeters, the rate of attenuation and degradation of sound signals varies largely
in different communication systems. As a result, the active range of a sound signal
covers probably hundreds of kilometers for marine mammals, several kilometers
for elephants, to less than 1 m in some grasshoppers. This chapter examines some
mechanisms by which these different animals achieve a maximum range of
communication. In particular, I will show how sound interference in stratified
environments can dramatically influence communication distance, and how
animals adapt their timing and location of the site of their signaling to these
environmental conditions.
Key words Thermal gradients, sound transmission, active space
1 Introduction
This chapter focuses on one limited aspect of acoustic communication, by
assuming that selection drives signals and signaling behavior towards greater range
and conspicuousness. The assumption, however, that acoustic signals of all species
should have design features to maximize the range of communication is not
correct. Communication between mates or parents and their young often ocurrs
over short ranges, and natural selection may favor a range of the signal over the
minimal distance necessary. Similar arguments hold for acoustic signals involved
in maintaining territories (review in Wiley and Richards 1982). Certainly, a
conspicuous signal may be advantageous, for example in mate attraction, but it
may also have costs. For example, predators and parasitoids are known to home in