Vibration Communication in Vertebrates
131
the bannertail kangaroo rat (Dipodomys) of the southwestern United States uses a
vibrational signal as an intermediate component of its communication system. The
list of potential vertebrate seismic communicators includes Bushveld rain frogs
(Breviceps) from the Republic of South Africa and the common Malaysian
treefrog (Polypedates) among others.
3.1 A Test Case - Leptodactylus albilabris - the White-Lipped
Frog
Males of most species of frogs and toads produce airborne species-specific
advertisement calls to signal their reproductive readiness and locations to
potential mates. In addition, several species of frogs are known to produce
substrate-borne vibrational signals which may also communicate biologically
significant information.
The white-lipped frog of Puerto Rico, Leptodactylus albilabris, is the first
vertebrate for which anatomical, neurophysiological, and behavioral evidence has
been brought to bear implicating the use of seismic signals in intraspecific
communication (Narins and Lewis 1984; Lewis and Narins 1985).
This animal has the physical means for generating, the sensory apparatus for
detecting, and access to a channel for transmitting vibratory signals between
conspecifics. Males of this species vocalize while partially buried in the muddy
soil. During the call, the vocal sac expands explosively, striking the substrate as it
inflates.
The resulting thump generates a vertically polarized Rayleigh wave (Fig. 1)
which propagates in the muddy soil outward in all directions from the source at a
velocity of roughly 100 ms- 1 , or about 113 the velocity of sound in air at sea level.
3.1.1 How Does a Frog Detect Extremely Small Motions of the Substrate?
It has been known for many years that the inner ear of anuran amphibians (frogs
and toads) is highly sensitive to substrate-borne vibrations (Ashcroft and Hallpike
1934), but only more recently has this sensitivity been quantified (Koyama et al.
1982; Narins and Lewis 1984; Lewis and Narins 1985; Christensen-Dalsgaard and
J0rgensen 1988; J0rgensen and Christensen-Dalsgaard 1991 ).
Anatomical and physiological studies have shown that the vibration sensitivity
of terrestrial frogs resides principally in the sacculus of their inner ear (Koyama et
al. 1982; Lewis et a!. 1982; Christensen-Dalsgaard and J0rgensen 1988;
Christensen-Dalsgaard and Narins 1993). The sacculus is an otolithic organ
containing a membranous sac filled with a slurry of dense calcium carbonate
crystals.
The 3000 sensory hair cells in the sacculus of the North American bullfrog
(Rana catesbeiana), are concentrated in a macula with their stereocilia in contact
131
the bannertail kangaroo rat (Dipodomys) of the southwestern United States uses a
vibrational signal as an intermediate component of its communication system. The
list of potential vertebrate seismic communicators includes Bushveld rain frogs
(Breviceps) from the Republic of South Africa and the common Malaysian
treefrog (Polypedates) among others.
3.1 A Test Case - Leptodactylus albilabris - the White-Lipped
Frog
Males of most species of frogs and toads produce airborne species-specific
advertisement calls to signal their reproductive readiness and locations to
potential mates. In addition, several species of frogs are known to produce
substrate-borne vibrational signals which may also communicate biologically
significant information.
The white-lipped frog of Puerto Rico, Leptodactylus albilabris, is the first
vertebrate for which anatomical, neurophysiological, and behavioral evidence has
been brought to bear implicating the use of seismic signals in intraspecific
communication (Narins and Lewis 1984; Lewis and Narins 1985).
This animal has the physical means for generating, the sensory apparatus for
detecting, and access to a channel for transmitting vibratory signals between
conspecifics. Males of this species vocalize while partially buried in the muddy
soil. During the call, the vocal sac expands explosively, striking the substrate as it
inflates.
The resulting thump generates a vertically polarized Rayleigh wave (Fig. 1)
which propagates in the muddy soil outward in all directions from the source at a
velocity of roughly 100 ms- 1 , or about 113 the velocity of sound in air at sea level.
3.1.1 How Does a Frog Detect Extremely Small Motions of the Substrate?
It has been known for many years that the inner ear of anuran amphibians (frogs
and toads) is highly sensitive to substrate-borne vibrations (Ashcroft and Hallpike
1934), but only more recently has this sensitivity been quantified (Koyama et al.
1982; Narins and Lewis 1984; Lewis and Narins 1985; Christensen-Dalsgaard and
J0rgensen 1988; J0rgensen and Christensen-Dalsgaard 1991 ).
Anatomical and physiological studies have shown that the vibration sensitivity
of terrestrial frogs resides principally in the sacculus of their inner ear (Koyama et
al. 1982; Lewis et a!. 1982; Christensen-Dalsgaard and J0rgensen 1988;
Christensen-Dalsgaard and Narins 1993). The sacculus is an otolithic organ
containing a membranous sac filled with a slurry of dense calcium carbonate
crystals.
The 3000 sensory hair cells in the sacculus of the North American bullfrog
(Rana catesbeiana), are concentrated in a macula with their stereocilia in contact