AN ECONOMIC THRESHOLD MODEL FOR HOUSE MOUSE DAMAGE TO INSULATION

Commensal rodents have become increasingly troublesome and damaging pests in insulated structures. Modern poultry and livestock confinement buildings in the Midwest often have insulated walls and ceilings. These buildings usually provide an optimum habitat for rats and mice; the rodents gnaw, tunnel through, and nest in the insulation, decreasing its insulative value. Such structures are known to be heavily damaged within a matter of months when commensal rodents have access to wall spaces and attics. We have developed an economic threshold model to help livestock producers or building managers decide when to conduct house mouse (Mus musculus) control in such situations. The model is based upon the cost of house mouse damage to commonly used types of insulation in walls, as measured in laboratory experiments. Components of the damage are 1) the cost of insulation replacement and 2) increased heating costs due to damaged insulation. Damage costs are compared to the expense of conducting mouse control using anticoagulant rodenticides in permanent bait stations located throughout the structure. The model concludes that it is cost-effective to implement a baiting program for mouse control in nearly all insulated confinement buildings. The cost of control is usually very small when compared to the cost of potential mouse damage