To prevent rodent entry, their capabilities must be understood. For example,
run along or climb electrical wires, pipes, fences, poles, ropes, cables, vines, shrubs, and trees to gain entry to a building (Fig. 2);
climb almost any rough vertical surface, such as wood, brick, concrete, weathered sheet metal, and many plastic products;
crawl horizontally along or through pipes, augers, conveyors, conduit, and underground utility and communications lines;
gnaw through a wide variety of materials, including lead and aluminum sheeting, window screens, wood, rubber, vinyl, fiberglass, plastic, and low-quality concrete or concrete block.
|Fig. 2. Rat traveling along an electric wire.|
crawl through or under any opening higher or wider than 1/2 inch (1.3 cm)
climb the outside of vertical pipes and conduits up to 3 inches (7.6 cm) in diameter; climb the outside of larger pipes attached to buildings by bracing themselves between the wall and the pipe; climb the inside of vertical pipes, wall voids, or earthquake safety seams and joints between 1 1/2 and 4 inches (3.8 and 10.2 cm) in diameter;
jump from a flat surface up to 36 inches (91 cm) vertically and as far as 48 inches horizontally;
drop 50 feet (15 m) without being seriously injured;
burrow straight down into the ground for at least 36 inches (91 cm);
reach as high or wide as 13 inches (33 cm);
swim as far as 1/2 mile (800 m) in open water, dive through water traps in plumbing, and travel in sewer lines against a substantial water current. In areas where high rat populations exist, it is common for both roof rats and Norway rats to enter buildings through toilets and uncovered drains.
House mice can:
enter openings larger than 1/4 inch (0.6 cm);
jump as high as 18 inches (46 cm) from a floor onto an elevated surface;
travel considerable distances crawling upside-down along screen wire;
survive and reproduce at a temperature of 24oF (-4oC) if adequate food and nesting material are available.