Acoustic Behavior 
293 
appear to be largely restricted to adults, with 
males being more vocal. 
Calling Periodicity 
In the remaining analysis of the vocaliza- 
tion of geckos, I shall deal only with multi- 
ple chirps. There are many references to 
gecko diel calling periodicity in the litera- 
ture. Brain (1962) states that Ptenopus 
garrulns produces calls in the late afternoon 
that increase in frequency until sundown and 
then decrease during the night. Haacke 
(1969) agrees with Brain, but mentions that 
on some days occasional calls may be heard 
all day long. Evans (1936) described an in- 
crease in calling by Gymnodactylus kotschyi 
in the evening as the animals fed. Calling in 
H. frenatus is restricted during high winds 
and rain (Marcellini, 1974), whereas calling 
in Ptenopus is said to be stimulated by rain 
(Haacke, 1969). From the above, it is ap- 
parent that geckos call most commonly when 
light intensities are low, especially at dusk. 
Description of Calls 
Comparative information about multiple 
chirp calls have been largely provided by 
three investigators (Haacke, 1969 ; Franken- 
berg, 1974; Marcellini, 1974). The loudness 
of multiple chirp calls ranges from the very 
low intensity sounds of Phyllodactylus 
tuherculosus that can only be heard from a 
few meters to those of Gekko gecko that can 
be heard from 200 m and more (personal 
observations). The loudness of the calls of 
some small species is impressive, the calls 
of Ptyodactylus hasselquistii and H. frenatus 
being discernible from 50 to 100 m (Frank- 
enberg, 1974; Marcellini, 1974). 
The frequency range of multiple chirp 
calls ranges from 500 to 10,000 Hz ; dominant 
frequencies are usually between 500 to 6000 
Hz. The lowest dominant frequency has been 
recorded from Gekko gecko (personal obser- 
vations), the highest from Ptyodactylus. 
The number of chirps per call is variable 
within individuals (Marcellini, 1974), be- 
tween subspecies ( Frankenberg, 1974) and 
between species (Haacke, 1969). The call 
rate is also highly variable, ranging from 
a low of 0.5 chirps per second for Gekko 
gecko to nearly 9.0 per second for Ptenopus 
(Haacke, 1969). The number of chirps and 
call rate appears to be dependent on the 
animal’s “emotional” state, and may also be 
affected by the environmental temperature 
(Marcellini, 1974). Haacke (1969) demon- 
strated that midnight and morning were 
slower than those of the evening when tem- 
peratures were higher. Frankenberg (1974) 
found no direct correlation between the rate 
of calls and fluctuating temperature and ob- 
served an overall increase in call rate with 
a rise in temperature. An effect of tempera- 
ture on call rate might be expected in view 
of findings on insects and anurans (review 
by Frings and Frings, 1962; Blair, 1963). 
Temporal patterns with respect to clicks 
and pauses of gecko calls have been reported. 
Haacke (1969) recognizes a consistent pat- 
tern in the calls of Ptenopus garrulus. 
Frankenberg (1974) has also shown pattern 
consistency in Ptyodactylus. These data and 
the findings on H. frenatus (Marcellini, 
1974) indicate that geckos have consistent, 
reproducible, temporal patterns in their 
multiple chirp calls. 
Species Specificity of Gecko Multiple 
Chirp Calls 
Calls produced by an individual may vary 
in number of chirps but are remarkably uni- 
form in structure (Frankenberg, 1974; 
Marcellini, 1974). Frankenberg has reported 
change in individual call structure of 
Ptyodactylus in different contexts. Male- 
male calls differ from male-female calls in 
being more protracted, although chirps are 
similar in structure and frequency. Haacke 
(1969) describes two distinct calls in one 
population of Ptenopus garrulus that may 
also be contextually related. 
Haacke (1969) shows two types of calls 
differing in number of chirps and temporal 
