Behavior and Neurology of Lizards 
N. Greenbe' c and P. D. MacLean, eds. 
NIMH, 1978. 
Display and Dispute Settlement in Nesting Iguanas 
A. Stanley Rand 
Smithsonian Tropical Research Institute 
and 
William M. Rand 
Department of Nutrition and Food Science 
Massachusetts Institute of Technology 
SUMMARY. In this paper we describe a study that resulted from combined research interests 
in (1) the ecology and behavior of a specific lizard, Iguana iguana; (2) the overall pattern and 
outcome of disputes between animals, and (3) the general stochastic modeling of behavior situa- 
tions. 
We describe the nesting behavior of female iguanas in Panama to illustrate the disputes that 
occur over nest burrows in a communal nesting site (Rand, 1968) ; then we discuss the process 
involved in settling these disputes, including the role of display and the importance of energy 
factors. 
INTRODUCTION 
In our approach it is assumed that a dis- 
pute occurs when two animals meeting in a 
conflict situation “disagree” about its out- 
come, In most social situations one sees little 
serious disputing; one animal is recognized 
as dominant and is deferred to rather than 
challenged. Animals fight only when they 
differ about which is going to dominate. 
Thus each conflict situation essentially in- 
volves the value of what is sought after ; the 
cost of contesting for it, and the probability 
of winning. We attempt to apply these ideas, 
derived from Game and Decision Theory, to 
the behavior of nesting iguanas. 
When one tries to fit any kind of model to 
the real world, the first problem is that of 
identifying the various factors — in this case 
those factors which should affect the animal’s 
behavior. The probability of winning can be 
evaluated by going into the field and count- 
ing frequencies of wins and losses in different 
situations. This is a standard approach, and 
we think it is a reasonably valid one. Eval- 
uating the worth of the prize and the cost of 
winning is more difficult. We argue that, in 
the “iguana” situation, we can reasonably 
evaluate both in terms of energy : the energy 
available to and the energy expended by an 
individual iguana. 
In terms of evolutionary time we subscribe 
to the view that costs and benefits are to be 
evaluated on the basis of fitness ; it is on fit- 
ness that selection acts. But fitness in ani- 
mals as long lived as iguanas is not easy to 
measure during the time available to a biol- 
ogist. The “decisions” an animal must make 
in specific situations affect its fitness; selec- 
tion, it may be supposed, acts to maximize 
fitness and determines the animal’s strate- 
gies. A species which is well adapted will 
“make decisions” that, on the average, opti- 
mize its fitness. The assumption of adapta- 
tion is essential since it allows one to say 
that what one observes is the animal max- 
imizing its fitness. 
In the situation of iguanas it appears that 
energy considerations are among the most 
important factors and that these are used 
in their “decisions.” An approach using 
energy to evaluate evolutionary strategies is 
familiar to ecologists in the form of energy 
budgets (Gates, 1965, and others) and in 
feeding strategy models (Schoener, 1971, 
and others). We have encountered no ap- 
proaches quite comparable to ours in be- 
havioral analyses. 
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