LIMITED ALTRUISM

This applet simulates agents ("foragers") with different feeding habits competing for food resources ("plants") and investigates the conditions under which foragers exhibiting altruistic tendencies prosper at the expense of selfish relatives.

There are two possible altruistic traits coded into the simulation: alarm calling and prudent predation. In the alarm calling scenarios, altruistic foragers will "warn" all other foragers of a potential attack by a predator, thus alerting others to the presence of a predator, but advertising their own location. In the case of a feeding restraint, the altruistic foragers will only ever eat half of a plant on a given cell. Plants grow according to a logistic growth rate equation; selfish foragers eat 99% of the plant, which means it takes a long time to recover and regrow.

The simulation can proceed with pure or mixed populations of species. All foragers eat to gain energy and reproduce asexually when their energy exceeds a threshold value, with their kin inheriting their altruistic/selfish trait and occupying a nearby free cell. The size of the foragers on the cell indicates their relative energy.

The distribution of plants and resource density may be varied; either random plant distributions at any density may be selected, or "clumped" resources, separated by barren lands of a certain size. The size of a plant is indicated by the "greenness" of the cell, altruistic foragers as yellow, selfish as purple.

To run the simulation, choose the altruistic trait to model, the resource distribution of plants, then press "Reset". This can be done as many times as you like to generate different starting criteria. The initial numbers of selfish and altruistic foragers [callers] add up to 40. So for example, to start with 10 selfish foragers and 30 altruistic foragers, type 30 in the "No. of Callers" box. "Start" and "pause" buttons are self explanatory.


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