11 



among the species studied. Time of activity, habitat, and food were 

 the niche gradients measured. There appears to be a high overlap be- 

 tween _C. tigris and the third teiid species present, _C. scalaris . 

 Close observation of their ecologies at a finer level reveals many 

 small differences between them, and these are examined. They may be 

 assumed to be potentially competitive. Frequent interspecific aggres- 

 sive encounters occur in the field in which _C. tigris always chases C_. 

 scalaris away. It is suggested that in a highly heterogeneous, unpre- 

 dictable ecosystem like the Mapimi the small ecological differences 

 mentioned greatly facilitates the coexistence of these two species. 

 It is further suggested that the very diversified ecological opportun- 

 ism of _C. scalaris allows it to colonize periodically the ecosystem 

 where _C. tigris is dominant in only a small number of biotopes. 



18. Barden, A. 19'^2. Activity of the lizard, Cnemidophorus sexline- 

 atus . ECOLOGY 23(3): 336-3^^. 



Laboratory experiments were done on lizards from Kansas and Indi- 

 ana to elucidate potential parameters controlling activity. Activity 

 rhythms are partially endogenous and partially controlled by environ- 

 mental factors such as light and temperature, with increasing day length 

 implicated as triggering spring emergence from hibernation. 



19. Beargie, K. M. L. 1971. The cranial morphology of the Teiid 

 genus Cnemidophorus. PH.D. DISS., UNIV. OF COLORADO. 175 p. 



The abstract is not informative, but the work is probably perti- 

 nent to this report. The author cannot afford to purchase it, and the 

 University of Colorado will not lend the work. 



20. Benes, E. S. 1969. Behavioral evidence for color discrimination 

 by the whiptail lizard, Cnemidophorus tigris . COPEIA 1969(^): 707-722. 



12 lizards, _C. t. mundus and _C. _t. tigris, were trained to feed 

 against a background of colored discs. The lizards were divided into 

 two equal groups and individuals were presented with a pair of discs 

 from which to feed. One group fed undisturbed from red discs and was 

 given an electric shock when attempting to feed from green ones; the 

 other group underwent the reverse procedure. The initial disc pair was 

 quite divergent in color; the pairs became closer and closer in color 

 to each other on successive trials. The lizards in each group learned 

 from which color disc they could feed successfully. Red colors tend to 

 be less acceptable and green colors more difficult to learn to reject 

 than the reverse situation. Cnemidophorus tigris can make fine distinc- 

 tions in color differences and is also capable of a generalized color 

 reaction. It is suggested that warning colors of unpalatable prey can 



