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Peter M. Narins
after the playback. In contrast, similar numbers of drumming sequences were
initiated before, during and after the stimuli played back through the air.
Moreover, by measuring the sound pressure inside a simulated kangaroo rat's
chamber in response to a mixed seismic-plus-airborne stimulus such as an
artificial thump, it was determined that in all cases tested, more than 98% of the
peak acoustic power in the thump sound recorded in the chamber was transmitted
directly through the ground from the site of the thump, and then radiated into the
chamber.
Thus, it was concluded that the acoustic power transmitted through the ground
was radiated by the chamber wall as airborne sound. It is of interest that sound
enters the burrow chamber via the seismic channel 40 dB louder than sound
entering from the air, down the chamber entrance. Thus on windless nights these
animals are able to communicate out of the burrow to distant neighbors via
airborne sound, and on windy nights inside the burrow to close neighbors (Randall
and Lewis 1997). Remarkably, the banner-tailed kangaroo rat has evidently
evolved an efficient communication system that utilizes seismic signals as an
intermediate "carrier" of information ultimately broadcast (by the chamber walls)
and detected in air.
3.9 Chamaeleo calyptratus - the Veiled Chameleon
Veiled chameleons are aggressive, brightly colored animals with a very high
(nearly 5 em) laterally compressed parietal crest (casque). They inhabit Yemen's
high, dry plateau and may grow to 38 em (Martin 1992). They spend the majority
of their time in trees in which they forage for food, mate, and carry out other life
functions. When handling chameleons, it is common in some species to feel a
buzzing or vibrating sensation (D. Lawson, pers. comm.). Vibration production in
response to touch has been reported in several species of chameleons in the genus
Brookesia (Raxworthy 1991; Glaw and Vences 1994) and Rhampho/eon
(Raxworthy 1991). Recently, accelerometer measurements taken from a plant on
which a male Chamaeleo calyptratus was perched revealed a conspicuous
vibratory signal emanating from the body just anterior to the front legs (Barnett et
al. 1999). When a female was placed on a plant with an adult male, he produced a
variety of distinct vibratory signals. Signals were recorded in bouts of 1-14 notes,
typically with a series of higher-pitched, shorter signals followed by one longer,
low-pitched signal. These signals were accompanied by either head tilting or
shaking.
The fact that these signals were produced only in the presence of a receptive
female or when individuals were startled by direct touch suggests that they serve a
communicative function. This is the first example reported of plant-borne
vibration communication by a reptile, and again emphasizes the often cryptic
nature of this signaling modality.
Peter M. Narins
after the playback. In contrast, similar numbers of drumming sequences were
initiated before, during and after the stimuli played back through the air.
Moreover, by measuring the sound pressure inside a simulated kangaroo rat's
chamber in response to a mixed seismic-plus-airborne stimulus such as an
artificial thump, it was determined that in all cases tested, more than 98% of the
peak acoustic power in the thump sound recorded in the chamber was transmitted
directly through the ground from the site of the thump, and then radiated into the
chamber.
Thus, it was concluded that the acoustic power transmitted through the ground
was radiated by the chamber wall as airborne sound. It is of interest that sound
enters the burrow chamber via the seismic channel 40 dB louder than sound
entering from the air, down the chamber entrance. Thus on windless nights these
animals are able to communicate out of the burrow to distant neighbors via
airborne sound, and on windy nights inside the burrow to close neighbors (Randall
and Lewis 1997). Remarkably, the banner-tailed kangaroo rat has evidently
evolved an efficient communication system that utilizes seismic signals as an
intermediate "carrier" of information ultimately broadcast (by the chamber walls)
and detected in air.
3.9 Chamaeleo calyptratus - the Veiled Chameleon
Veiled chameleons are aggressive, brightly colored animals with a very high
(nearly 5 em) laterally compressed parietal crest (casque). They inhabit Yemen's
high, dry plateau and may grow to 38 em (Martin 1992). They spend the majority
of their time in trees in which they forage for food, mate, and carry out other life
functions. When handling chameleons, it is common in some species to feel a
buzzing or vibrating sensation (D. Lawson, pers. comm.). Vibration production in
response to touch has been reported in several species of chameleons in the genus
Brookesia (Raxworthy 1991; Glaw and Vences 1994) and Rhampho/eon
(Raxworthy 1991). Recently, accelerometer measurements taken from a plant on
which a male Chamaeleo calyptratus was perched revealed a conspicuous
vibratory signal emanating from the body just anterior to the front legs (Barnett et
al. 1999). When a female was placed on a plant with an adult male, he produced a
variety of distinct vibratory signals. Signals were recorded in bouts of 1-14 notes,
typically with a series of higher-pitched, shorter signals followed by one longer,
low-pitched signal. These signals were accompanied by either head tilting or
shaking.
The fact that these signals were produced only in the presence of a receptive
female or when individuals were startled by direct touch suggests that they serve a
communicative function. This is the first example reported of plant-borne
vibration communication by a reptile, and again emphasizes the often cryptic
nature of this signaling modality.