Spatial and Breeding Relationships of the Lizard, Anolis Carolinensis: Evidence of Intrasexual Selection

Abstract

1. We used continuous 8-day monitoring to document the spatial and mating relationships of free-ranging Anolis carolinensis lizards at each of seven habitat-delineated study sites. 2. We found a polygynous social structure, consisting of a male and 2-6 resident females (x = 3.3), on each site. 3. Spatially, both sexes utilized all available perch heights and diameters on the study sites (habitat generalists), though females tended to perch slightly higher and on significantly thinner substrata (x = 2.4 m, 3.4 em, respectively) than males (x = 2.3 m, 5.3 em, respectively). 4. Mean home range volume was eight fold greater for males (69 m3) than females (8 m3). Male home ranges were exclusive of other males (0% overlap), while neighboring female home range volumes overlapped an average of 18%. 5. Male snout-vent length (SVL) was positively correlated with male home range size (area, volume) and with number of resident females, but not with resident female SVL or resident female home range size. 6. Half of 397 male-female encounters led to close contacts in which males influenced courtship outcomes by: recognizing receptive and non-receptive females (differential display rate); bypassing 69% (85/123) of mating opportunities with receptive females; and copulating only when courtship was male-initiated. 7. Larger males (who also had larger territories and more females) courted less per female, but with longer duration, and had longer copulatory durations than smaller males. 8. Male frequency of copulation (x = once/1.4 days), however, had no correlates with measured variables; females were mated without bias to male or female attributes. 9. Male potential reproductive rate (PRR), estimated from the number of copulations with different females, positively correlated with male SVL. Female PRR, estimated from the inter-mating interval (i.e. the single-egg clutch interval), did not correlate with any measured male or female trait. 10. Our data, in concert with other field studies and A. carolinensis life history traits, document a polygynous mating system in which females seem to fit a 'no cost, neutral-mate-choice' model, and males (in response to sedentary, contiguously distributed females who clutch at weekly intervals over a 4-month period) employ territorial contests within an endurance rivalry as a prime mechanism for mate assortment.