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1 January 2000 Sexual Dimorphisms in Aggressive Signal Structure and Use by a Polygynous Lizard, Anolis carolinensis
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Unlike many polygynous species, we found that females of the lizard, Anolis carolinensis, have the same repertoire of aggressive signals as males. These shared signals included three stereotyped headbob display patterns (types A, B, and C) that were performed with no significant intersexual difference in amplitude displacement. However, we did find the following sexual dimorphisms in signal structure and use. Females (1) had a smaller average extendable throat fan (i.e., dewlap) area (0.22 cm2) than males (1.52 cm2), (2) never displayed when alone (0/h), whereas males frequently did (18/h), (3) displayed 10-fold less during consexual encounters (17/h) than males (168/h), (4) lacked the ritualized intermale combat scheme of circling, jaw-sparring, and jaw-locking, (5) infrequently used physical contact in consexual encounters, whereas males frequently did, and (6) did not employ a shifting use of signals with decreasing interfemale approach distance, whereas contesting males did by decreasing the frequency of C displays in favor of A and B displays, decreasing the use of the dewlap during displays, and decreasing the sequencing of displays in volleys. These results are in accord with field studies, which report limited interfemale territoriality (i.e., low consexual threat) and short display broadcast distances, whereas male territorial behavior is well developed (i.e., high consexual threat), with frequent long-distance displaying between consexuals. We suggest that these displays, which function in competitive interference, have been less directionally selected in females than in males because the outcomes of consexual contests carry fewer reproductive consequences for females than for males.

The American Society of Ichthyologists and Herpetologists
Thomas A. Jenssen, Kimberly S. Orrell, and Matthew B. Lovern "Sexual Dimorphisms in Aggressive Signal Structure and Use by a Polygynous Lizard, Anolis carolinensis," Copeia 2000(1), 140-149, (1 January 2000).[0140:SDIASS]2.0.CO;2
Accepted: 8 July 1999; Published: 1 January 2000

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