A. ROSS KIESTER (MCZ) has divided his time between theoretical and 
experimental work, 
One paper (with M. W. Slatkin) investigates the consequences of the 
hypothesis that some species of iguanid lizards (including certain species 
of Anolis) have evolved a strategy of resource utilization in which indi- 
viduals take into account the distribution of conspecifics in the environment 
in addition to the distribution of food resources, Kiester and Slatkin 
propose that the two cues are integrated by their effect on the time budget 
of an individual lizard. Thus, a model of the time budget of a lizard is 
used to formulate a model of the tendency to movement of an individual 
which in turn is used to infer the pattern of movement within a population. 
Computer analysis of the final difference equation and mathematical analysis 
of a differential equation approximation to the difference equation yield a 
picture of the pattern of movements of lizards in a changing environment. 
The analyses also lead to three qualitative results which differentiate the 
conspecific cuing model from strategies based on cuing on the resource alone: 
1) Gaps may exist in the equilibrium distribution of lizards even if the 
resource is continuous, 2) the speed of movement of a population is propor- 
tional to local population size, and 3) the systems response is most sensitive 
to changes in the propensity of individuals to move. The quantitative pattern 
of movement together with these three qualitative results help to understand 
the biology of certain species of lizards, possibly including such anoles 
as A, lineatopus and A. aeneus, 
A series of laboratory experiments on the choice behavior related to 
conspecific association in the Panamanian grass anole (Anolis auratus) 
demonstrated that auratus of both sexes would approcah another auratus 
regardless of sex. These experiments have been detailed in the previous 
grant report. In order to bolster the interpretation of the laboratory 
experiments, Kiester with G. C. Gorman devised a series of field experiments 
to be performed on A. auratus and on two Puerto Rican species (A. pulchellus 
and A. cristatellus). The field experiments made use of a particular 
behavior shown by these lizards when disoriented, which Kiester and Gorman 
term post-vantage behavior. Performing it, a lizard crawls slowly up a 
branch or twig which projects out of the grassland habitat in which it 
normally lives and moves and then surveys the surrounding area in all 
directions before climbing back down and heading off. An artificial post 
was used which had two long ramps running off in opposite directions. A 
lizard placed on the top of the post would then survey the area and would 
then crawl down to one or the other of the ramps and on it to the ground, 
The post and the ramps were set up in such a way so that the ramps each led 
to a qualitatively different habitat, The lizards could thus choose a 
habitat in the field. In the experiments with A. auratus, the lizards 
significantly often chose a grassland habitat over a bush habitat, demon- 
strating that post-vantage behavior and movement directly afterwards was 
effective in finding the correct habitat. Anolis pulchellus, offered a 
