Female Morphs, Uta stansburiana

Orange females are r-strategists as they tend to have smaller offspring and more of them, a “quantity over quality” approach. Yellow females are K-strategists as they produce large eggs and are favored at high density, a “quality over quantity” strategy. Each strategy has its advantage depending on the density of the population at that time, which cycles between low and high density every other year. Yellow females do well in high-density years, as their offspring are larger and thus better able to outcompete the orange females smaller offspring. On the flip side, orange females are more successful in low-density years as they are able to have more offspring that can quickly take over the landscape.  You can see in the photos below examples of eggs from yellow (left, smaller) and orange (right, larger) females’ eggs. To read more on how these cycles are supported by natural selection please see the publication linked below.

Sinervo, Svensson, Comendant – 2000 – Density cycles and an offspring quantity and quality game driven by natural selection

Synopsis of female behavior. The outcome of male and female encounters depends on the receptivity cycle of the female. If the female is receptive, copulation is possible. However, before or after the critical 3-4 day window of receptivity the female can reject a courting male. Before receptivity, the female rejects the male with a tail flick (this is because the male tries to grab the females tail in his mouth prior to copulation — see the full copulation movie). After receptivity, the female rejects the male with a vigorous and rapid series of head bobs, along with a humped posture. She will also act aggressively towards the male. Of course, males need not be harrassing the female to incur female aggression. Males often do dumb things (see the movie on Aggression).

 

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