Ilaria Bertazzi

Computer Science and Simulation for Economics

Project work on

"Hunting economy and common assets."


The applet requires Java 1.4.1 or higher. It will not run on Windows 95 or Mac OS 8 or 9. Mac users must have OS X 10.2.6 or higher and use a browser that supports Java 1.4. (Safari works, IE does not. Mac OS X comes with Safari. Open Safari and set it as your default web browser under Safari/Preferences/General.) On other operating systems, you may obtain the latest Java plugin from Sun's Java site.

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view/download model file: hunting_economy_and_common_assets.nlogo


This is a simulation that aims to investigate the ability of survival and welfare of a community of hunters in case there is the possibility of creating an inventory of captured prey available to the community.
The model is based on the work of Bowles and Choi ["The First Property Rights Revolution", 2002]


The program creates a number of agents prey (called kudu) and agents hunters, split between active and free-riders.
The agents prey follow a cycle of moving-eating-reproduction.
The hunters have a repository at the center of the world at their disposal. The patches in this area accumulate energy each time a prey is captured, and that energy remains available whenever their energy falls below the "warning-energy".
Active agents hunts and moves, free riders do not move and they eat only from the warehouse.
Hunters and free-riders have a variable called social-indorsement, which increases if they are active hunters, and decreases in case they are opportunists. Below the level "Tollerance" of this variable, the agents free-rider become active.
Huntsmen have a countdown that decreases only when free-riders exceed 1 / 5 of the total population. When the countdown reaches zero, they become opportunists.
Reproduction of human agents is linked to the presence of energy storage, energy of each agent and fertility ("Men-reproduce ")


Among the variables controlled by sliders there are:
last-of-food: duration of food in repository.
Tollerance: minimum level of social approval, to move from opportunists to hunters;
social-blame: social indorsement removed every tick for opportunists;
men-reproduce: Fertility, probability of reproduction of each agent.

The Setup button creates a number of initial kudu and men, the huntsmen agents are red while the opportunists blue.
GO button turns the simulation using the parameters set.


With a initial setting near to:
last-of-food: 5 ;
percentual-of-opportunists: 20 or more;
tollerance: 20 ;
social-blame: 5;
energy-from-kudu: 30 ;
It may happens sometimes that all opportunists disappear, or that the percentual become near to 50% and the level remains constant.

With a initial percentual of opportunists lower than 20% no huntsman can become opportunist in any case.


A point to expand is the opening / closing of the repository to allow or not to free-riders to access it.
It may be interesting to link the reproduction to the presence of stocks in the warehouse in recent periods, not only in the present moment.
The expansion may simulate more complex agents who do not hunt but can not be considered “free riders” as other possible components of a community (Craft, mothers, children ...) that entirely depend from the storage and that are necessary to the community. Extending this aspect would make the model more realistic.


"The First Property Rights Revolution" Samuel Bowles and Jung-Kyoo Choi, 2002