66 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 122 



this is visibility. In veiy dense vegetation it might be possible for 

 two A. lineatopus to have overlapping home ranges and seldom meet. 

 I do not think this is of great importance, for most home ranges have 

 perches from which much of the area can be seen and it is on these 

 that the lizards spend most of then- time. But the presence of a 

 large male in a brush heap for several days, even though he was 

 repeatedly chased by the resident males, suggests that overlapping 

 home ranges are at least temporarily possible. The importance of 

 visibility was emphasized for A. sagrei on Bimini by Oliver (1948), 

 who reported that the territories became larger and that less overlap 

 was tolerated when a hurricane increased visibility by defoliating the 

 habitat. 



Agonistic behavior of the sort shown by A. lineatopus can regulate 

 density only by forcing individuals to move away, since fights to the 

 death are rare, if in fact they ever occur. Subadult, young adult 

 males, and young females do move considerable distances and may 

 settle, at least for short periods, in previously unoccupied areas 

 (p. 29 et seq.). Further, a number of these young males were found 

 to be living in areas that for one reason or another seemed to be sub- 

 preferable for the species. It seems likely that they had been forced 

 to move by aggressive behavaor on the part of other lizards and 

 forced to settle in unoccupied places because the preferable ones 

 were already occupied. 



The evidence suggests that the social organization in A. lineatopus 

 tends to set an upper limit to the population density in a particular 

 structural environment and to force the excess lizards, particularly 

 young males and, to a lesser extent, young females, to disperse. 



How far these ^. li7ieatopus travel during dispersal we have no idea; 

 consequently, it is impossible to judge the importance of social orga- 

 nization in promoting panmixis in the population or in extending the 

 distribution of the species. Certainly that there is dispersal at all 

 reduces the amount of close inbreeding. That the dispersal may take 

 lizards into previously uninhabited areas indicates that it plays some 

 part in extending the distribution of the population. 



It has also been suggested that the spacing out of individuals in an 

 area may act to reduce both predation and disease. Both of these are 

 possible but seem unlikely in A. lineatopus. In spacing out individuals 

 it is possible that fewer are found by predators, but A. lineatopus are 

 most conspicuous when they are displaying and fighting. The in- 

 creased conspicuousness to a predator must at least partially offset 

 any advantages gained by over-dispersion. 



We know almost nothing about disease in lizards but it is possible 

 that the spatial isolation that the social behavior produces may act to 

 reduce the spread of infectious diseases. Two facts, however, argue 



