Display Diversity 
279 
In a nonanoline species, Berry (1974) 
found a population-wide head-bobbing pat- 
tern in Sauromalus obesus consisting of a 
single fast bob, two bobs of longer duration, 
and then one or more single fast bobs. The 
pattern was quite stereotyped in individuals 
(Berry, 1974) but showed interindividual 
variations in the cadence and bob amplitudes. 
Intra-population variability refers to dis- 
play elements (especially modifiers) having 
a wide range of expression which can vary to 
a similar extent in the displays of all popula- 
tion members. These display elements can 
function as indicators of relative arousal. 
For example, the signature display of A. 
limifrons has display components which are 
a source of variability shared by the entire 
population (Jenssen and Hover, 1976). The 
stereotyped portion of the signature display 
consists of seven head bobs having a cadence 
within the first five bobs of one long, three 
short, one long (Figs. 10 and 11). However, 
the addition of dynamic modifiers can alter 
the overall pattern. Many of the seven-bob 
signature displays are performed with a 
preceding introductory head roll and two 
additional bobs at the end of the display 
(Fig. 8Ao) ; however, the stereotyped seven- 
bob pattern can be elaborated to an even 
greater extent (Fig. SA^). The optional 
introductory movements can vary in ampli- 
tude, and the optional terminal head bobs 
can vary in number from none to ten. The 
addition of the dynamic modifiers to the 
UNITS I I 
SECONDS 
Figure 10. DAP graph of the signature display of 
Anolis limifrons. Stippled areas indicate display 
portions not always present. Bar below DAP 
graph gives mean total duration of the first seven 
head bobs (vertical line), the standard error of 
the mean (outer ends of small white boxes), and 
95 percent confidence limits of the mean (outer 
ends of small black boxes). 
seven-bob core display was not specific for 
individuals ; it was an option performed to a 
similar extent by all the observed males. 
In his review. Carpenter (1967) describes 
many species of lizards as being able to 
vary the relative bob amplitude between 
display performances. As the lizards become 
more aroused, head amplitude grades from 
being primarily effected by neck muscles, to 
displays having head bobs produced with 
forelimb extension and flexion, and finally to 
displays in which all four limbs are creating 
the bob pattern. Thus, the optional use of 
the limbs to produce vertical body movement 
can be classified as a dynamic modifier. The 
ability to use this optional display element 
and the range of expression is shared by a 
population, making the modifier an example 
of intra-population variability. 
Pattern variability refers to aspects of the 
core display which are expected to be con- 
sistent for the displays of a population, but 
which are altered to the extent that the 
display pattern is changed. 
Pattern variability can occur on the in- 
dividual level when a few individuals of a 
population may, for instance, occasionally 
drop a bob or add an extra dewlap pulse 
to the stereotyped portion of their display. 
HEAD BOB UNITS 
Figure 11. Mean duration for each of the first seven 
head-bob units of 316 Anolis limifrons signature 
displays. Horizontal line indicates unit mean, 
outer white bars denote standard error of the 
mean, and outer black bars provide 95 percent 
confidence limits of the mean. 
