# Predator-Prey Behaviour in Self-Replicating Interstellar Probes

## TL;DR

This paper models predator-prey dynamics of self-replicating interstellar probes using Lotka-Volterra equations, finding that such interactions do not sufficiently suppress probe populations to resolve Fermi's Paradox.

## Contribution

It applies predator-prey models to interstellar probes, revealing stable populations and oscillatory behaviors that challenge the idea of probes being undetectable due to predator-prey interactions.

## Key findings

- Many stable solutions with large probe populations exist.
- Oscillatory predator-prey dynamics can occur depending on parameters.
- Prey often outnumber predators, not resolving Fermi's Paradox.

## Abstract

The concept of a rapid spread of self-replicating interstellar probes (SRPs) throughout the Milky Way adds considerable strength to Fermi's Paradox. A single civilisation creating a single SRP is sufficient for a fleet of SRPs to grow and explore the entire Galaxy on timescales much shorter than the age of the Earth - so why do we see no signs of such probes? One solution to this Paradox suggests that self-replicating probes eventually undergo replication errors and evolve into predator-prey populations, reducing the total number of probes and removing them from our view. I apply Lotka-Volterra models of predator-prey competition to interstellar probes navigating a network of stars in the Galactic Habitable Zone to investigate this scenario. I find that depending on the local growth mode of both populations and the flow of predators/prey between stars, there are many stable solutions with relatively large numbers of prey probes inhabiting the Milky Way. The solutions can exhibit the classic oscillatory pattern of Lotka-Volterra systems, but this depends sensitively on the input parameters. Typically, local and global equilibria are established, with prey sometimes outnumbering the predators. Accordingly, we find this solution to Fermi's Paradox does not reduce the probe population sufficiently to be viable.