   House Mice - January 18, 2006 Jeff Schalau, County Director, Associate Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Last year’s wet winter was a boon to small rodents including wood rats, gophers, squirrels, and house mice. The house mouse (Mus musculus) is a common pest in houses and outbuildings. It is well adapted to sharing our living space and resources and has been doing so for thousands of years. These little pests can share other things with us too: like diseases and parasites. This column will explain their life cycle, habits, and preferences in order to help you understand and control them. House mice are much smaller than rats and can be distinguished from a juvenile rat by their smaller feet and head. Their fur is usually a dusty gray above and cream colored on the belly. They can also be identified by their droppings which are 1/8 to 1/4” inch (3 to 6 mm) long and rod-shaped with pointed ends. Other signs of house mice are: gnaw marks on wood, cardboard, and soft plastic; tracks/footprints (4 toes on the front 5 toes on the rear feet); rub marks (dirty areas along base boards and walls); and damaged goods such as cereals and seeds. House mice reach sexual maturity in 35 days and the female’s gestation period averages 19 days. The young are born blind and hairless except for whiskers and are weaned after about 3 to 4 weeks. Average litter size is 6 and each female can bear about 8 litters per year. They usually live for about a year, but have been known to live as long as 6 years. Mice are mainly nocturnal but can sometimes be seen during the day. They have keen senses of smell and hearing but poor eyesight. On a rough surface, they can run up a wall, jump 12” up in the air, and can jump down 8 feet and survive. A mouse requires 1/10 oz. of food per day. Free water is not necessary because they can get it from their food. However, if free water is available, they will drink it. They really like sweetened beverages such as cherry flavor Koolaid and prune juice. One mouse produces 50 droppings per day. Mice are very social. Related males and females are compatible, but unrelated mice are typically aggressive toward each other. One male dominates the territory over other lower-ranking males. The territory may also include several females and all mature mice tend to show aggression toward strangers within their territory. Mice are very inquisitive. If something has changed position or is out of place, they will explore it and adjust their travel routes accordingly. There are two main feeding periods: at dusk and just before dawn. They will also nibble on small amounts of food anytime. They prefer to nest in dark, secluded places with abundant nesting material close by. The material may be cotton, packing material, insulation, or fabric. Adult mice can also squeeze through an opening 1/4” or larger to gain entry. The most threatening health issue with mice is their ability to spread Salmonella bacteria in their droppings. This organism is a common cause of food poisoning. Other transmittable organisms are tapeworms, rat-bite fever, infectious jaundice/leptospirosis/ Wiel’s Disease, plague, Hantavirus, and possibly poliomyelitis (polio). Given these potentially life threatening diseases, mice should not be tolerated in your living space. To reduce indoor mouse populations, you should start by trying to exclude them and eliminate access to food sources, water and shelter. If this is done and the problem continues, then you should consider population control. That’s right, I am suggesting lethal means. Real mice are not like Stuart Little. They don’t drive miniature sports cars and talk. The old standby is the snap trap set and placed along a well-traveled wall. I usually bait traps with peanut butter, oat flakes, and bits of raison. Glue boards and sticky traps are also available, but may be considered less humane. Do not touch the dead mice (or any dead animal) with bare hands. Use disposable rubber gloves or a plastic bag over your hand, bag the dead mouse, and discard in an outdoor waste recepticle. Wash thoroughly with soap and water after disposal. Toxicants (poison baits) and anti-coagulant rodenticides can be used as well, but the dead mice may smell badly if they die inside the house. Multi-capture, live traps also work well. One of these is called the “Tin Cat”. They enter and cannot exit. Once one mouse enters, other mice also become curious and enter too. With these devices, you will need to decide how to dispose of the live mice once they are caught. Pest control professionals often use carbon dioxide chambers to humanely asphyxiate the trapped mice. The presence of mice in sheds and barns often attracts other predators including snakes, owls, coyotes, bobcats, and foxes. Cats and dogs can also help control mice. This time honored tradition works fairly well, but they don’t need to go hungry to encourage them to hunt. Supplemental food should always be provided. The University of Arizona Cooperative Extension has publications and information on gardening and pest control. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at mgardener@verdeonline.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. |