​Muskrat model from SDS Summer School 2015.  Suppose there is a muskrat plague in a particular area. At first, there were 100 muskrats. The autonomous increase in the number of muskrats per muskrat per year amounts to an average of 20 muskrats per muskrat per year. Suppose that each year, 10 licences are granted to set muskrat traps. The licences are only valid for one year and each person holding a licence may set 10 traps.  Assume the number of muskrats caught per trap is proportional to the number of muskrats and a catch rate per trap which is close to 0.2, say, on average 0.2, minimally 0.195, and maximally 0.205.