Using boids, it is easy to set animations with some prey/predator-like behaviour to some extend. In these cases, using Spherical Fieds emitters with negative Strength (repulsive, predators) or positive Strength (attractive, preys) will be quite easy and effective. Moreover, using the Die on Hit option (in the Extras panel) would prove useful also, when a predator successfully reaches a particle.
This tutorial is designed for Blender 2.46 and supplements Blender 2.46's release Logs about Boids particles systems. You need a SVN version of Blender to use it! Special thanks go to Janne Karhu for all the cool tips he provided me, both for the documentation and this tutorial.
Usage of Boids for a prey-predator simulation
For Blender: 2.46