Animals Gnaw on Electrical Wires

12.14.2003 - One of the greatest dangers of having wild animals living in your attic is that they can cause destruction, in particular, to electrical wires.  Many animals like to gnaw and chew, but most cases of wire destruction are from rodent species - squirrels and rats.  I have been in thousands of attics so far in my career as a wildlife removal specialist, and a good percentage (more than not) of the houses with rodent infestations have some extent of chewing on the electrical wires.  The four photos above represent just a few of the cases I've seen so far.

A rodent's teeth grow continually, much like our fingernails.  Just like a cat has to scratch its claws to keep them in check and we trim our nails, a rodent has to gnaw to keep their teeth at the proper size.  They gnaw on many surfaces.  I often see extensive damage to the wood in an attic.  They just seem to like to chew on wires sometimes.

The two primary problems with wire damage like this are first, that it can cause a fire hazard, and second, that it can cause electrical shorts.  Of the two, the former is of course the larger concern.  I've noticed that many rodents tend to travel along the wooden beams in the attic, and they often choose to gnaw on the wires that lay across these beams, such as in the lower-right photograph.  If they gnaw down to the copper, and that copper touches the wood, you've got a chance for a house fire!  It's estimated half of fires of unknown origin are from rodent wire damage.  I don't know how true this is, but do know that it does happen.

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I've also seen several cases in which animals have become electrocuted and died on the wires, and caused shorts.  Customers have told me, "this side of the house lost power" or similar things, and then electricians discovered rodent chewing, and then I was called out to fix the rodent problem.  I've been to a few homes in which chewing rats and squirrels have set off security systems, when they chewed on the security system wires.

Also, I've been to four homes so far which have had a re-plumbing job.  That means that new PVC water lines have been installed through the attic and walls, to replace the copper lines that were under the house.  Rodents chew on these lines as well, and then you've got a water leak in the attic that comes down through the ceiling.  It's a big problem when this happens.

For these reasons and more, if you have rodents living in your attic, it's more of a problem than just dealing with some scratching and scampering noises in the night.  Rodents in the attic pose a serious risk to your property and safety, because of their gnawing behavior, and tendency to gnaw on electrical wires.

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Animals gnaw on electrical wires for two reasons: either when the wire obstructs its way, or when the animal gets idle and feels like chewing on something to prevent teeth overgrowth. While you may find it strange to chomp down on an electrical wire, some wild animals enjoy doing it to soothe and perhaps have fun. Therefore, having such animals around your home and in your attic may culminate in extensive damage to your property.

Most wild animals in the attics, crawl spaces, and walls are likely to gnaw and chew on electrical wires whenever it obstructs their way. But, the most notorious ones are rodents such as rats, mice, and squirrels. Therefore, you need to be on the lookout for these animals and keep them off your property if at all you want to protect your property from accidental fires caused by damaged electrical wires.

Apart from electrical wires, rodents will chew a lot of surfaces, including wood, ductworks, and water pipes. Although there are many reasons why these animals gnaw on electrical wires, the main reason is to prevent over-growth of their teeth. Their teeth grow continuously, just like our fingernails or a cat's claws.

Just like you trim your nails to stay short, if these rodents don't chew, their teeth may grow too long for their mouths. Long teeth will hinder eating and lead to starvation and death. Therefore, when rodents find an electrical wire to gnaw, they will enjoy every bit of it. But guess what? That's where the trouble lies. In case the bare wires come into contact, the resulting event is an accidental fire outbreak that could wreak havoc on your entire property if the situation gets out of hand.

Why is it possible for the rodents to chew up anything that comes their way? Well, rodents have specialized adaptations that enable them to gnaw and chew electrical wires. For instance, rats and mice have sharp incisors that grow continuously. As such, they will always chisel their teeth by grinding on wires. The incisors are curved, enabling them to apply pressure to the electrical wires and gnaw and chew the hard material.

What Could Be the Risk of Animals Gnawing on Electrical Wires?

Rodents can cause considerable damage to your electrical connection if they gnaw on them. The most common problem caused by these creatures is power outages or electrical shorts. That is why you may experience blackouts in some parts of your house. They may also chew wires that connect your AC to the power, thereby causing the device not to function.

The wire damage can also cause a fire hazard. When these rodents gnaw the electrical wires that are often laid across the wooden beams on your attic, the copper wire may touch wood, leading to a fire outbreak. Most of the fires from unknown causes are suspected to be from wire damage by rodents. In some cases, these messy animals have been setting off security systems by chewing on the systems' wires, exposing such homes to burglary. The animals have also become victims of their actions. At times, they get their fair share by being electrocuted to death by live electrical wires.