INTRODUCTION
Rats and mice often enter homes, farm buildings, and warehouses in search of food and shelter. Rats and mice have been carried by man to every corner of the earth, where they consume or contaminate large quantities of food and damage structures, stored clothing, and documents. They also serve as reservoirs or vectors of numerous diseases. The most common rodent pests in Nevada are Old World species called the pocket rats that have adapted to live with man. They include roof rats, house mice, escaped lab and pet rats (in Las Vegas), and mice.
In most cases of rodent infestation, the pest animals can be controlled without having to resort to the use of poisons. The practices of good sanitation and exclusion will prevent most problems. If rodents do find their way indoors, small populations can be easily eliminated with various nontoxic methods. Rodenticides (rodent poisons) need only be used in cases of large or inaccessible infestations. The trapping of rodent pests is often preferable to the use of poisons, because traps prevent rodents from dying in inaccessible places and causing an odor problem. There is no chance of an accidental or secondary poisoning of non-target wildlife, pets, or children with the use of traps. Secondary poisoning of pets or wildlife can result from eating poisoned rodents. Traps can be used in situations where poisons are not allowed or recommended such as in food handling establishments.
Nevada has several species of native rodents and it is important to distinguish between native and non-native species. The native rodents, such as pack rats (wood rats), grasshopper mice, deer mice, pocket mice, and kangaroo mice that occasionally invade rural and suburban homes can be released back in the wild
RODENT ECOLOGY – “KNOW YOUR OPPOSITION”
The presence of mice is usually indicated by sightings, damage from gnawing into food containers, or presence of droppings. The house mouse is the most common commensal rodent invading urban homes in Nevada. It is secretive and primarily nocturnal. In the wild, house mice feed primarily on seeds. In the home, they prefer grain products, bird seed, and dry pet food. They tend to nibble on many small meals a night. House mice are good climbers. They have small home ranges and usually stay within 10 to 30 feet of their nest. Therefore, traps for mice should be set 6 to 10 feet apart. Nests are usually in structural voids, in undisturbed stored products or debris, or in outdoor burrows. When food is abundant, nesting material such as a cotton ball attached to a trap trigger can act as an effective lure. Mice and rats are very nervous about moving in the open. The more cover they have, the more comfortable they are. They would prefer running behind an object or along the baseboard of a wall to running across an open area. Therefore, hiding traps in cabinets, closets, and along walls is most effective. Peanut butter or gumdrops stuck to the trap triggers, or peanut butter mixed with rolled oats or birdseed are good baits. Since house mice are inquisitive and actively explore anything new, moving traps and baits into new areas is effective.
The roof rat or black rat is the most common rat encountered in urban Nevada. These rats are excellent climbers and often nest in attics, wall voids, hollow trees, and in palm thatch and dead fronds. They prefer to travel off the ground and enter houses from nearby trees or along power lines. Roof rats prefer fruit (they are sometimes called fruit rats), but will eat any type of human, pet, or livestock food. Peanut butter, pieces of fruit or nut meats are the best baits. Different from mice, rats are usually fearful of new items in their environment and avoid them for several days. An exception to this would be the wood rat. This means that traps should be left in place for at least one week before they are moved to a new location. The presence of roof rats can be detected by gnawing damage, the presence of droppings, sightings, scratching sounds, squeaking or gnawing in walls or ceilings, and characteristic dark greasy rub marks along frequented paths such as walls and rafters. Rats have large home ranges and may travel over 50 yards to reach food or water. Concentrating traps along rat runways or favorite routes of travel is most effective.
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