NO- 3595 ANOLIS LINEATOPUS — RAND 65 



population density in favorable situations. The tliii'd, the distri- 

 bution of the adult males with respect to potential mates, affects the 

 adult males most du'ectly. 



Considering fii-st the lizard's relation to food supply, we have abeady 

 seen that A. lineatopus feeds largely within its home range and largely 

 on insects it sees from its principal perches. I have also shown that 

 there is a tendency for different sized A. lineatopus to eat different 

 sized food. The spacing out in an area of indi^aduals of the same size 

 means that there are fewer times when two A. lineatopus attempt to 

 catch the same insect and consequently compete directly for food. 

 Also, smce the lizards' activity ranges are nonoverlapping, the lizards 

 cover the maximum area possible and a particular insect is most 

 likely to land in the feeding area of one of them. The overlapping 

 of feeding areas of A. lineatopus of dift'erent sizes means that a greater 

 size range of the insects within an area are potential food to the A. 

 lineatopus living there. Thus, both the spacing out of individuals of 

 the same size and the overlap of those of different sizes increases the 

 probability that a given insect will be eaten b}^ an ^4. lineatopus wher- 

 ever the insect lands. 



From this discussion it appears quite possible that one of the 

 important ecological residts of the social organization of -^4. lineatopus 

 is in the decreasing of intraspecific competition for food and the 

 hicreasing of the efficiency with which the available food supply is 

 exploited. 



It has been suggested that territorial behavior (which is frequently 

 so defined as to include the social system described herein) has an im- 

 portant function in regulating density in favored areas. In A. 

 lineatopus there is a lower limit set by the structm-e of the en\^ron- 

 ment below which acti\'ity ranges cannot be compressed, i.e., the 

 number of available perches. Particularly with adult males, but 

 even with smaller individuals, most perches are indivisible; they are 

 occupied by only one A. lineatopus of a particidar size. In areas where 

 the only perches are scattered trees or fence posts, the social behavior 

 interacts with the structure of the envu'onment to limit population 

 density. If there were more trees or fence posts, there could be 

 more A. lineatopus. But, if ^4. lineatopus peacefully shared perches, 

 there could be more of these lizards in the same number of trees. 



In more complex structural habitats, the situation is not so clear. 

 The general constancy of home range size in several rather different 

 places suggests that there is a size limit below Avhich home ranges 

 cannot be compressed. This in tm*n suggests that even in complex 

 environments, social organization may act as a means of limiting 

 population density. There is another element in the structm-e of the 

 en\ ironment other than available perches that may affect density and 



240-241—67 5 



