Stochastic control model with carrying capacity of population management policy for squirrels in durian orchards

Abstract

In this thesis, the problem that squirrels ruin durian, which is an economic important fruit in Thailand, is considered. We seek for a strategy on squirrel elimination under the consideration that squirrels are not alien species in Thailand and also orchard ecosystem. The problem is solved through a stochastic control model. The population dynamics of squirrels is constructed as a controlled stochastic differential equation with carrying capacity, since we consider the squirrel population in a confined orchard. A performance index indicating the total benefit of a given squirrel elimination strategy is provided. The index comprises the countermeasure cost, resources loss, and squirrel's benefit. The optimal performance index is numerically solved through the variational inequality using the finite difference method. The corresponding optimal strategy to control the squirrel population is also given numerically.