136
Peter M. Narins
in the auditory domain. Our current work seeks to extend these exciting results to
bimodal units.
3.2 Spalax ehrenbergi- the Blind Mole-Rat
Blind mole rats (Spa/ax ehrenbergi) are highly solitary and extremely aggressive
and live in individual tunnel systems where they rarely encounter each other
except during the mating season (N evo 1961 ). In a landmark study, Rado et al.
(1987) demonstrated both with captive and wild blind mole rats that headdrumming responses could be elicited by finger tapping and scratching by the
experimenter on the substrate. In a subsequent study, it was suggested that (1) the
unique morphology of the middle ear of Spa/ax and of the articulation between the
lower jaw and the skull, and (2) a peculiar jaw listening behavior enable substrateborne vibrations to be transmitted to the inner ear mainly by bone conduction
(Rado et al. 1989). This might be seen as compensating for the restricted range of
airborne signals to which this animal is sensitive (Bruns et al. 1988; Heffner and
Heffner 1992).
More recently, Rado et al. (1998) showed that the seismic signals that mole rats
use for long-distance communication are processed primarily by the auditory
rather than the somatosensory system. Clearly, these fossorial mammals have used
the properties of seismic signals to their advantage for intraspecific
communication. As we shall see, Spa/ax is not alone among the mammals in its
exploitation of substrate-borne signals.
3.3 Georychus capensis - the Cape Mole-Rat
African mole-rats in the family Bathyergidae comprise five genera, living in a
wide range of habitats. Three of the genera are solitary for some part of their lives,
the most extreme case being the Cape mole-rat, Georychus capensis, which
spends the vast majority of its life under Africa, alone in its burrow, save for a
short period during each breeding season. This monotypic genus appears to be
most closely related to two other solitary mole-rat genera, Heliophobius and
Bathyergus, and less closely related to the social Cryptomys and Heterocephalus
within the Bathyergidae (Honeycutt et a!. 1991 ).
Males and females each construct complex burrow systems of approximately
130m length and mean diameter 10 em in sandy clay soils (Du Toit eta!. 1985;
Narins eta!. 1992). Burrow systems of Georychus approach within a few meters
of each other and are rather evenly spaced (Davis and Jarvis 1986; Bennett and
Jarvis 1988a). Individuals of Georychus produce sexually dimorphic patterns of
foot-druming in the laboratory and in the field, and it is possible that these signals
are used for maintenance of spacing and communication between individuals. It is
Peter M. Narins
in the auditory domain. Our current work seeks to extend these exciting results to
bimodal units.
3.2 Spalax ehrenbergi- the Blind Mole-Rat
Blind mole rats (Spa/ax ehrenbergi) are highly solitary and extremely aggressive
and live in individual tunnel systems where they rarely encounter each other
except during the mating season (N evo 1961 ). In a landmark study, Rado et al.
(1987) demonstrated both with captive and wild blind mole rats that headdrumming responses could be elicited by finger tapping and scratching by the
experimenter on the substrate. In a subsequent study, it was suggested that (1) the
unique morphology of the middle ear of Spa/ax and of the articulation between the
lower jaw and the skull, and (2) a peculiar jaw listening behavior enable substrateborne vibrations to be transmitted to the inner ear mainly by bone conduction
(Rado et al. 1989). This might be seen as compensating for the restricted range of
airborne signals to which this animal is sensitive (Bruns et al. 1988; Heffner and
Heffner 1992).
More recently, Rado et al. (1998) showed that the seismic signals that mole rats
use for long-distance communication are processed primarily by the auditory
rather than the somatosensory system. Clearly, these fossorial mammals have used
the properties of seismic signals to their advantage for intraspecific
communication. As we shall see, Spa/ax is not alone among the mammals in its
exploitation of substrate-borne signals.
3.3 Georychus capensis - the Cape Mole-Rat
African mole-rats in the family Bathyergidae comprise five genera, living in a
wide range of habitats. Three of the genera are solitary for some part of their lives,
the most extreme case being the Cape mole-rat, Georychus capensis, which
spends the vast majority of its life under Africa, alone in its burrow, save for a
short period during each breeding season. This monotypic genus appears to be
most closely related to two other solitary mole-rat genera, Heliophobius and
Bathyergus, and less closely related to the social Cryptomys and Heterocephalus
within the Bathyergidae (Honeycutt et a!. 1991 ).
Males and females each construct complex burrow systems of approximately
130m length and mean diameter 10 em in sandy clay soils (Du Toit eta!. 1985;
Narins eta!. 1992). Burrow systems of Georychus approach within a few meters
of each other and are rather evenly spaced (Davis and Jarvis 1986; Bennett and
Jarvis 1988a). Individuals of Georychus produce sexually dimorphic patterns of
foot-druming in the laboratory and in the field, and it is possible that these signals
are used for maintenance of spacing and communication between individuals. It is