The ontogeny of display behavior in Sceloporous undulatus hyacinthinus (Sauria: iguanidae)

Abstract

Displays of 36 Sceloporus undulatus hyacinthinus from 8 clutches were recorded on video tape from the day of hatching to adult size during 1978, 1979, and 1980. Nine hundred forty-one displays were analyzed frame by frame, and durations of display units were calculated to the nearest 0.01 s.

From the day of hatching, males and females performed both of the display types found in adults, and little significant ontogenic change was found in display patterns or in unit durations; only 7% and 6% of total variance in A and B Displays, respectively, was due to ontogeny. Stereotypy of unit durations both within and among lizards was unchanged across time. Consequently, the display patterns are viewed as being purely innate.

Some ontogenic changes were observed in the ways in which the lizards utilized the displays patterns. As compared with hatchlings, older lizards tended to display more frequently, to use display modifiers more often, and to perform displays in aggressive and courtship contexts as well as in assertion. Older females had a significantly higher A: B ratio than males or younger females. These changes in display behavior are viewed as being due to the influences of hormones and social experiences.

Slightly more than half of the variance in unit durations for A and B Displays was attributed to inter-individual differences. Of this, approximately half was due to differences among clutches and half to differences among lizards within clutches. For B Displays there were some inter-individual differences (e. g., deleted bobs or dips preceding certain bobs) in the form of the displays as well as in unit durations. Individuals were not consistent in the inclusion of these characteristics in their B Displays.

Mean heritability estimates for durations of units 1-12 were 0.60 and 0.38 for A and B Displays, respectively.