294 
Marcellini 
pattern, within the Ptenopm garrulus 
maculatus subspecies. Haacke also describes 
differences in number of chirps per call in 
animals on opposite sides of a 150 m wide 
sand dune. Frankenberg (1974), on the 
other hand, found calls within a subspecies 
to be remarkably consistent and distinctive 
for that subspecies. 
Variation of calls between species has 
been mentioned by Haacke (1969) who states 
that each species of Ptenopus has a different 
call that can be recognized by differing call 
rates and number of chirps per call. Werner 
(1965), in his study of Ptyodactylus in 
Israel, states that the males of two species 
produce different calls. 
Figure 5 shows sonograms of male 
Hemidactylus frenatus. H. turcicus, and 
Phyllodactylus tuberculosus recorded at ap- 
proximately the same temperature. In the 
sonogram of H. turcicus, the calls of two 
individuals are superimposed ; only the 
stronger five-chirp call should be focused on. 
Species differences in duration of pauses and 
chirps, intensity pattern of chirps, and 
physical characteristics of the chirps are 
apparent. The call of H. turcicus has longer 
pauses and a concomitant lower call rate 
than those of the other two species. In H. 
frenatus and H. turcicus, the individual 
chirps appear to decrease in intensity from 
first to last. The dominant frequency of the 
calls is approximately the same, but har- 
monics for H. turcicus are much closer 
together than those for H. frenatus. 
Table 2 gives the call parameters for 9 
species and subspecies of geckos. Although 
the sample sizes are small, there are evident 
differences between species and subspecies 
in all three parameters of the call. Ptenopus 
kochi and P. hasselquistii guttatus and P. h. 
puiseuxi differ in dominant frequency and 
call rate. Gekko gecko appears to have a 
lower dominant frequency and slower call 
rate than the other geckos. 
Although the calls of many species and 
subspecies of geckos differ in many respects, 
it would be premature to postulate taxon- 
specific calls on the basis of the limited ob- 
servations. More data are needed in order 
to determine quantitatively the degree of 
variation within individuals, between popu- 
lations, subspecies, and species. When such 
data are available, we may be able to utilize 
acoustic behavior in conjunction with other 
evidence to solve taxonomic problems. 
Functional Significance of the Multiple 
Chirp Call of Hemidactylus frenatus 
I have made observations on the functional 
significance of the multiple chirp call of H. 
frenatus utilizing an experimental procedure 
in which individual females and males were 
exposed to the male multiple chirp in a choice 
situation (Marcellini, 1977). Females made 
no directed response to the male multiple 
chirp call, and seemed weakly stimulated to 
move (Table 3). Males gave a significant 
negative response to the call and were more 
active (Table 4), indicating that the call 
might function to establish and maintain 
territories. 
Comparison of Visual and Acoustic Displays 
Adaptation to a nocturnal existence by 
gekkonid lizards required a number of 
changes in their behavior and ecology. One 
important change involved display behavior. 
Lizards ancestral to geckos, were, no doubt, 
diurnal (Underwood, 1954; Kluge, 1967) 
and, like modern iguanids and agamids, 
probably utilized visual channels for intra- 
specific communication. Residual parts of 
these displays can still be seen even in noc- 
turnal geckos. Hemidactylus frenatus pos- 
tures during close-range encounters between 
individuals. 
Males in high intensity aggressive en- 
counters hold their head low and their back 
arched as they approach an antagonist. Other 
nocturnal geckos such as Phyllurus platurus, 
Teratoscinus scincus, and Nephrurus asper 
are known to have visual components in 
their threat displays (Mebs, 1966, 1973; 
Bustard, 1967&). The limited usefulness of 
visual displays for distance communication 
