BLUE-BELLIED LIZABDS 



627 



Under original conditions the Blue-bellied Lizards lived chiefly upon 

 and around rocks and trees, and this is still true in most of the Yosemite 

 region. The Tenaya Blue-bellied Lizards of the higher altitudes are almost 

 exclusively rock dwellers, whereas the Fence Lizards at the lower levels 

 on the west slope inhabit tree trunks, downed logs and, of course, rail 

 fences where these are available. Only seldom are these animals to be 

 found on the ground. There is thus with lizards, as with other vertebrates, 

 an ecologic segregation. The present species inhabits places above ground, 

 while skinks, whip-tails, and alligator lizards live on the ground. In the 

 high mountains the Tenaya Lizard when active resorts to the granite 

 boulders, while the Mountain Lizard {Sceloporus graciosus) is chiefly 

 terrestrial, and the Mountain Alligator Lizard strictly so. 



Fig. 61. Cross-section of the Sierra Nevada through the Yosemite region showing 

 the distribution of some reptiles and amphibians which are either restricted to or find 

 their maximum abundance in single life-zones. 



The fences built about pastures in the forest belt, especially those made 

 of split rails, are often occupied by numbers of these lizards. On one 

 occasion a member of our field party, while working in the neighborhood 

 of the McCarthy ranch east of Coulterville, estimated that there was one 

 lizard to every 50 feet of a given fence. 



In the territory occupied jointly by the Mountain Lizard (Sceloporus 

 graciosus) and representatives of the present group, the Blue-bellied 

 Lizards outnumber the smaller species. On the upper parts of the boulder 

 talus along the north side of Yosemite Valley beneath Eagle Peak the 

 proportion was about 25 of occidentalis to 10 of graciosus. On a trip to 

 Clouds Kest, from 6 to 12 Tenaya Blue-bellied Lizards were noted to each 

 Mountain Lizard, 



Fence Lizards are abroad and active during all the warmer months of 

 the year, but they spend the winter season, even at the lowest altitudes, 

 in hibernation. On January 8, 1915, two were found in a damp place 

 beneath a log at Snelling, "stiff in hibernation," as the collector says in 

 his notes. As soon as the days of spring come, with the sunlight and 

 warmth which induces growth in plants and activity in insects, these lizards 



