insect population dynamics

*To*: mathgroup at smc.vnet.net*Subject*: [mg24590] insect population dynamics*From*: Mark Hunter <mhunter at ecology.uga.edu>*Date*: Tue, 25 Jul 2000 00:56:21 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

I'm trying to use mathematica to run insect population models. I'm new to the system, and wolfram support suggested that I post my question here. The models are simple predator-prey models. They are non-linear simultaneous difference equations. I've tried using RSolve, but it doesn't seem to handle the non-linearity. Is there a way of using a Do-Loop for the same kind of thing? A simple example of the model that I tried is: RSolve[{a[n + 1] == a[n]*Exp[0.63((1 - a[n]/50)) - 0.068b[n]], b[n + 1] = a[n]*(1 - Exp[-0.068*b[n]]), a[0] == 25, b[0] == 10}, {a[n], b[n]}, n] I want an output for variables a and n at time n, n+1, etc. I'd be most grateful for any advice that you can offer, and please don't underestimate my current level of ignorance. Many thanks, Mark Hunter