There is a product on the market that traps and kills rodents by electrocution. The mice or rats are concealed from view because they are contained within a box once they are killed. By baiting them with something more tempting than your grain (peanut butter maybe?), you may succeed in keeping them away from the exhibit. I took the liberty of looking it up for you. The company is called Agrizap, and the product is called the "Rat Zapper." Thier web page is: http://www.agrizap.com/ I have no idea what these devices cost, but they can't be too expensive. I hope this helps. Regards, ------ Christian C. Burke Project Manager Inter-Con Security Systems, Inc. Los Angeles County Museum of Art <http://www.lacma.org>