Rock-Paper-Scissors

The rock-paper-scissors game and the evolution of alternative male strategies

An unusual game is being played out in the Coast Range of California. Three alternative male strategies are locked in an ecological “perpetual motion machine” from which there appears little escape. As in the rock-paper-scissors game where rock beats scissors, paper beats rock, and scissors beats paper, three morphs of lizards cycle from the ultra-dominant polygynous orange-throated males, which best the more monogamous mate gaurding blues; the oranges are in turn bested by the sneaker strategy of yellow-throated males, and the sneaker strategy of yellows is in turn bested by the mate guarding strategy of blue-throated males. Each strategy in this game has a strength and a weakness, and there is the evolutionary rub that keeps the wheels spinning. See the <href=”http: www.cisab.indiana.edu=”” lizards=”” jpegs=”” javalizards.html”=””>slide show for more details on the ESS analysis of the rock-paper-scissor game (B. Sinervo and C. M. Livley (1996) Nature 340:240-243). Photos on this page can be expanded by a click to get a higher resolution view. Some links that refer to behavior access the VIDEO Library or QuickTime movies.

lizard_headsThe Colors: Photos of the three flavors (orange, blue, and yellow) of male side-blotched lizards, shown in profile and from the bottom of the throat.

 

 

 

lizard_sexCopulation: These males spend most of their time trying to gain access to females. Warning: the following image shows lizards engaged in copulation…click at your own risk.

 

 

 

map_1994_72Territory map: Orange and blue males actively defend a territory. Yellow males tend to cluster around the territories of orange males, probably because they are more successful in sneaking copulations from the females on an orange male’s territory compared to sneaking copulations from blue males.

 

 

 

Summary

Thus, each strategy has a strength and a weakness and there are strong assymetries in contests between morphs. Trespassing yellows, with their female mimcry, can fool oranges. However, trespassing yellows are hunted down by blue males and attacked. While oranges with their high testosterone and high stamina can handily defeat blues, they are susceptible to the charms of yellows. In contrast, contests between like morphs (e.g., blue vs blue, orange vs orange or yellow vs yellow) are usually more symmetric.

                        Analysis of Head-Bob Patternsbob_frequency

The bobs can easily be analyzed by digitizing images and “slicing” through the video frames to get the outline of the lizard head bobbing up and down through time. This has been highlighted in red. The male in this sequence is participating in the “challenge” display. Yoni Brandt and I are busily analyzing such videos.