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Equipment Hub: Little mouse, big problems

Christine Gelley for Progressive Dairy Published on 31 December 2020

Why do rodents chew wires?

One-quarter of house fires with undetermined causes are assumed to be caused by rodents chewing on electrical wires.



This can also be the cause of many tractor malfunctions. With the risk of electrocution, it makes you wonder why would they chew on electrical wires in the first place?

Mpuse problems

The answer is easy. They chew on everything. Mice, rats and other rodents have teeth that are constantly growing, therefore they are constantly gnawing on any material they can find to file their teeth. Electrical wires are often hidden from view in places that are cozy for rodent nests and offer convenient access to wire insulation to chew. People rarely notice damage to the wires until an electrical system fails to work when they need it.

What is the big deal? It’s just a little mouse

Modern farm equipment operates on a series of electrical systems that connect systems to each other and enable safety functions. A weakness somewhere in the circuit could cause malfunctions to the main electrical system, throwing codes and triggering safety shut-offs.


For example, if a mouse exposes wires to a seat sensor, the motor may refuse to run because it seems the seat is empty. Imagine this happens to you. Your first idea may be to check if something is wrong with the motor or battery, but upon inspection you find nothing wrong and call your mechanic for help. Upon diagnosis, the issue traces back to the electrical system.

Your mechanic flips up the tractor seat and finds a mouse nest, damaged wiring and a faulty sensor. A mouse nest has now cost you hourly fees, parts and delayed work. In a worse scenario, the damage to the wire coating could be minor and just cause heat to emit from the wires, then short-circuit, spark and catch on fire, melting your wiring harness.

The damage can be frustrating, dangerous and expensive to repair.

How to keep rodents out

Traps and rodenticides are not very effective at controlling rodents on the farm. A barn cat is a helpful teammate, but the most effective control for rodents is preventing entry into storage spaces. It may seem impossible to seal every crack, but do the best you can. Mice can squeeze through areas that are a 1/4-inch squared and rats through a 1/2-inch squared. Adding hardware cloth to ventilation spaces can help prevent entry. Keep vegetation around storage buildings trimmed down to reduce hidden entries and passage corridors.

Rodent damage can also be an issue in frequently used machinery during the winter. Mice can scurry away while the equipment is running and return after it is parked to bask in the radiant warmth after you do chores. Both cabbed and open-station equipment can harbour rodents.


Remove any food or loose fabric material from your tractor cab to deter feeding and nest creation. Occasionally inspect your tractor throughout the winter to watch for nesting. Even if the cab or other compartments appear sealed, there may be alternative entry points, such as the wheel wells or the firewall, where they can enter and make a cozy nest.

Speaking from experience

My spouse is an ag mechanic, and he frequently shares stories from his day that involve rodent damage, electrical failure and even damage to cabin air filters. The photo shown here is an example of a rodent nest in a tractor that caused electrical system failures. A little mouse can cause big problems and go undetected by even the most experienced tractor operators.

Inspect your equipment before and throughout winter storage, as well as before use in the spring to scout for rodent damage in hidden spaces. Don’t forget to check your filters, batteries and tires for replacement or repair at the same time. Consider scheduling maintenance appointments in the off-season for swift return before the equipment is needed again in full force. end mark

PHOTO: Adding hardware cloth to ventilation spaces that are over 1/4-inch can help keep mice and rats from entering the space. Photo by Keegan Gelley.

Christine Gelley
  • Christine Gelley

  • Agriculture and Natural Resources Extension Educator
  • Ohio State University
  • Email Christine Gelley