Sex-specific visual performance: female lizards outperform males in motion detection

In animal communication, complex displays usually have multiple functions and, male and female receivers often differ in their utilization and response to different aspects of these displays. The perceptual variability hypothesis suggests that different aspects of complex signals differ in their ability to be detected and processed by different receivers. Here, we tested whether receiver male and female Sceloporus graciosus lizards differ in visual motion detection by measuring the latency to the visual grasp response to a motion stimulus. We demonstrate that in lizards that largely exhibit complex motions as courtship signals, female lizards are faster than males at visually detecting motion. These results highlight that differential signal utilization by the sexes may be driven by variability in the capacity to detect different display properties.

Measurement of Eggshell Thickness Between two Species of Sceloporus Lizards Using Scanning Electron Microscopy

Thermal environment exerts a strong influence on lizard life histories by constraining seasonal activity time, fecundity, growth, and embryonic development. in cold climates, extending the duration of egg retention within the female's body permits embryos to develop more rapidly than would be possible at ambient nest temperatures. The duration of egg retention time in the oviduct is largely constrained by the ability of the growing embryo to uptake oxygen and release carbon dioxide. Parchment shelled eggs of most squamates (lizards, snakes, and amphisbaenians) while permeable to water and gases, also acts as a diffusive barrier to gas exchange. As a result, most taxa with extended egg retention exhibit a concomitant reduction in eggshell thickness.To assess the influence of thermal environment on egg retention time, I sampled eggs from the lizards Sceloporus occidentalis and Sceloporus graciosus(Phrynosomatidae) from three populations at high, intermediate, and low elevation, in the San Gabriel Mountains of Southern California.