Hierarchy Entropy Degeneration Explains the Rat Utopia Population Collapse: The Role of Full Visibility and Isolation

TL;DR

This paper explains the rat population collapse in Calhoun's experiments by linking full visibility of social hierarchy to entropy degeneration, which reduces social engagement and leads to population decline.

Contribution

It introduces a novel hypothesis that hierarchy entropy degeneration caused by full visibility explains population collapse, supported by game-theoretic simulations.

Findings

Simulations replicate the population trajectory observed in experiments.

Hierarchy entropy decreases over generations, reducing social activity.

Full visibility of hierarchy leads to collapse due to loss of uncertainty.

Abstract

Calhoun's Rat Utopia experiments demonstrated a puzzling population trajectory: initial growth, plateau, and eventually a total collapse of the rat population despite abundant resources. This paper proposes a hypothesis that the enclosure's design enabled full visibility of the social hierarchy (pecking order), leading to entropy degeneration: progressive loss of uncertainty in rats' perceived ranks over generations. High initial uncertainty drives engagement in dominance, reproduction, and care; as visibility solidifies the hierarchy over the generations, uncertainty vanishes, nullifying perceived gains from social activities. Simulations reproduce the experimental arc which rely on a game theoretic matrix that is parameterized by the uncertainty (entropy) in the hierarchy which changes over rat generations.