The House Mouse: The House Mouse can carry many transmittable diseases. Prefer dark secluded areas to nest within any structure. Pregnancy lasts about 21 days producing 5 to 8 young. The female can have up to 8 litters per year. The young reach sexual maturity in 35 days.Life expectancy is about 1 year. They have keen senses except for sight. In 6 months a pair of mice will produce 18,000 droppings & 12 oz. of urine. An opening of ¼ of an inch will allow entry into a structure.