288 
Marcellini 
lacertids also squeal and hiss in response to 
predators (Falck, 1953; Simms, 1970; 
Klemmer, 1971; Vogel, 1973). Glass snakes 
have been reported to produce mewing 
sounds (Simmons, 1877) and day geckos 
(Phelsuma) have been heard to “purr like a 
kitten” (Demeter, personal communication). 
Cnemidophorus tigris, a teiid, can produce 
squeaks when handled (Campbell, 1966). 
Iguanids are also known to squeal and hiss 
in response to predators and during intra- 
specific interactions. Gambelia w. wislizenii 
(Weaver et al., 1966) and 13 species of 
Anolis (Milton, 1974) produce vocal sounds. 
Until the recent work on Anolis grahami 
by Milton (1974), little or no quantitative 
or experimental work had been done on the 
structure, contexts, and functions of the 
sounds of iguanid lizards. Milton’s work 
demonstrates that Anolis grahami can pro- 
duce more than one type of sound, but the 
sounds are apparently an antipredation de- 
vice and are incidental on the rare occasions 
when they occur during intraspecific inter- 
actions. In the terminology of the present 
paper, the sounds produced by A. grahami 
would be considered in the category “other 
sounds.” 
Integumentary sound production in liz- 
ards is known to occur in geckos of the genus 
Teratoscincus. These animals produce a 
hissing noise by rubbing caudal scales 
against one another. Werner (1967) has 
studied the morphology and regeneration of 
the caudal scales. The functional significance 
of the sound itself is not known. 
In lizards, true vocalizations are probably 
found only in the family Gekkonidae. These 
animals have long been renowned for their 
vocal abilities (Smith, 1849; Evans, 1936; 
Mertens, 1946; Loveridge, 1947), and many 
have both common and scientific names that 
reflect these abilities. The generic name 
Gekko is intended to resemble the sound pro- 
duced by these animals. Tokay, the common 
name for Gekko gecko, refers in Malay to 
the sound produced when the animal calls. 
The specific epithet in Ptenopus garrulus, 
also emphasizes the vocal nature of these 
animals. 
Many species of geckos have been reported 
to produce sounds. Table 1 provides a partial 
list, with comments on the types of sounds 
produced. It has been suggested that all 
geckos vocalize (Werner, personal communi- 
cation), and many more species could, no 
doubt, be added to the list. Species in the 
Eublepharinae are not very vocal, and ani- 
mals such as Coleonyx and Euhlepharis 
produce only squeaks and are not known to 
vocalize in the manner defined in this paper. 
Phelsuma and other diurnal geckos are also 
largely lacking in true vocalizations. The 
sounds produced by the members of the 
Eublepharinae and those of diurnal geckos 
are not known to fulfill any social function. 
True vocalizations are produced in only one 
subfamily of geckos. The Gekkoninae pro- 
duce a variety of types of calls in three basic 
categories : multiple chirps, churrs, and 
squeaks. Some of these calls appear to be 
involved in intraspecific communication and 
meet all the criteria for true vocalizations. 
As mentioned earlier, geckos are appar- 
ently unique among the lizards in possessing 
vocal cords (Gans and Maderson, 1973). 
Only one study has been done on the mech- 
anism of sound production. Paulsen (1967) 
studied sound production in the distress call 
(churr) of the tokay gecko and noted that 
the sound was produced by passing air be- 
tween tensed vocal cords that vibrate at 
right angles to the air stream. Dominant 
frequencies of the calls are between 40 and 
200 Hz, with changes in frequency deter- 
mined by the length of time the vocal cords 
lie in contact with each other. 
Sound Reception in Lizards 
Hearing in lizards has received a great 
deal of attention by Wever and his co- 
workers at Princeton (Peterson, 1966 ; Wever 
and Hepp-Reymond, 1967 ; Wever and 
Werner, 1970). A brief summary of the re- 
sults of these investigations follows. 
The work by Wever using cochlear poten- 
tials has shown that the acoustic apparatus 
in lizards is generally less sensitive than that 
