[Annual Rodent Control Issue] Why Do Rodents Gnaw?

By: Robert Corrigan

Rodents rely on gnawing as a means of survival in the wild. They use their incisors and powerful jaws to gain access to harborages, obtain daily resources such as food, water and nesting materials, assist in climbing, and as weapons against enemies.

By gnawing on and through wood, rodents create openings into tree trunks, hollow logs, or cut and clear through the thick roots of trees to hollow out nest cavities. Around and inside our buildings, rodents gnaw through doors, floors, windows and walls for the same purpose — to gain entrance to possible harborage and protective sites.

In the wild, food and moisture can be obtained by the rodent gnawing on various types of plants, seed shells, and tree bark. Larger food items are first nibbled into easy-to-handle sizes by the incisors prior to grinding with the cheek teeth. The stems of various plants often contain insect larvae and moisture that the rodent accesses via gnawing.

In addition, when the stem is felled via gnawing — much in the same way a beaver fells trees — the top of stems may reward the rodent with a nutritious seed head. And the stem itself, or the leaves growing along the stem, can be gathered and used as nesting material.
 

Why it Matters.

Of particular concern and interest is the rodent’s seemingly excessive attraction toward gnawing on man-made wires. Rodents attack utility wires, computer wires, the wires of our vehicles, and a wide range of other wires of different shapes, sizes and function.

Moreover, rodents often seem to “select” the critical current-carrying wires of electrical equipment. This is borne out in livestock and other agricultural facilities where rodents are major economic pests because of their repeated attacks on the wires of aeration fans and conveyor belts, resulting in expensive shutdowns of these facilities.

But as wires do not offer the rodent any nutritional return, what is it about wires that rodents find so attractive? Because such little research exists on this subject, nothing is known for sure. Perhaps wires appear visually similar to other items attractive to rodents, such as the familiar shape and diameter of plant stems and tree twigs. If indeed rodents also respond to the electrical current and vibration of a wire, perhaps the sound or vibration is similar to the rodent as that sound made by trickling water, or an insect feeding or traveling through plant stems.

Regardless, gnawing is a natural and necessary survival behavior of the rat and mouse. When they move into our buildings and equipment, rodents are simply behaving instinctively as they have for thousands of year. Being an opportunistic animal, the rodent has learned it has little to lose and usually much to gain by gnawing on the many objects encountered during its daily explorations.

About the author: Robert Corrigan is one of the world’s leading “rodentologists” and author of the book Rodent Control: A Practical Guide for Pest Management Professionals. Order it at www.pctonline.com/store.