Here's a stochastic interpretation of the Lotka-Volterra equations:

*
V' = beta*V - S*P*V*

P' = alpha*S*P*V - mu*P

(Mnemonics: *P* is predator; *V* is prey (victim); *beta* is the birth rate; *mu* is the death rate; *S* is the search rate; and *alpha* is how efficient predators are at turning prey into other predators.)
The sliders are parametrized in a sort of funny way; *beta*, *mu* and *alpha* vary between 0 and 1, whereas the maximum value of *S* is 0.001.

You can read details about the stochastic interpretation used here.