Behavior and Neurology of Lizards 
N. Greenberg and P. D. MacLean, eds. 
NIMH, 1978. 
The Acoustic Behavior of Lizards 
Dale L. Marcellini 
National Zoological Park 
Smithsonian Institution 
SUMMARY. The acoustic behavior of lizards is reviewed with emphasis on geckos. Many lizards 
emit sounds, but some geckos produce calls that have a consistent form and pattern and carry an 
intraspecific message. In the geckos, the subfamily Gekkoninae is the most vocal and emits calls 
in three basic categories: multiple chirps (MC), churrs, and squeaks. In general, hearing in 
lizards is less well developed than in a typical mammal, but within a restricted frequency range 
the acoustic sense may be as sensitive as that of mammals. The lizards with the most sensitive 
hearing are the geckos. The acoustic behavior of Hemidactylus frenatus is reviewed and com- 
pared to that of other gecko species. Similarities are found in (1) Type of calls produced; (2) 
contexts in which calls are emitted; (3) calling periodicity; and (4) structure of calls. The species 
specificity of the multiple chirp (MC) call of geckos is discussed and found to be population 
specific. Experiments on the functional significance of the MC call of H. frenatus indicate that 
it is implicated in territorial behavior. 
The contexts and functions of visual displays of iguanid lizards and the acoustic displays of 
geckos are compared and significant similarities between the two are described. 
INTRODUCTION 
Bioacoustics has made remarkable strides 
during the last decade. Work has been done 
on a wide variety of animal types, principally 
arthropods and vertebrates. The majority of 
the vertebrate investigations have dealt with 
four groups: fish, amphibians, birds, and 
mammals. The acoustic behavior of reptiles 
had been little studied until the last few 
years when work was undertaken with 
crocodilians (Campbell, 1973; Garrick, 1975) 
and turtles (Campbell and Evans, 1972). 
Lizard vocal behavior, even that of the very 
vocal geckos, has been largely ignored until 
recently. 
After a brief review of sound production 
and hearing in lizards and particularly 
geckos, I will describe some of my work on 
the acoustic behavior of Hemidactylus 
frenatus, including experiments on the func- 
tions of gecko calls. In conclusion, I will 
compare the vocal behavior of geckos with 
the visual displays of diurnal lizards. 
LIZARD SOUND PRODUCTION 
Sound production in reptiles has been 
recently reviewed by Cans and Maderson 
(1973). Sounds produced by lizards will be 
divided here into “vocalizations” and “other 
sounds.” A “vocalization” will be defined as 
an oral explosion that can be modulated, 
reproduced consistently in form and pattern, 
and carries some intraspecific message. 
“Other sounds” will apply to any sounds that 
do not fit the above definition. Included in 
this category are hissing, roaring, integu- 
mentary sounds, and some forms of squeaks. 
Geckos are apparently unique among lizards 
in possessing vocal cords (Gans and Mader- 
son, 1973). 
Many species of lizards in a number of 
families produce sounds other than true 
vocalizations. Chameleons are reported to 
hiss when approached by a predator and to 
bark during intraspecific encounters (Rosen, 
1950; Bustard, 1967a). Monitors hiss and 
squeal in similar contexts (Pianka, 1970; 
NZP Keepers, personal communications) and 
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