Species Report: The Problem With Squirrels

Five factors behind outages – and a way to prevent them

According to a 2016 American Public Power Association survey, animal incursion was the leading cause of outages at substations in the United States – and squirrels were by far the leading problem species. In fact, John C. Inglis, former deputy director of the National Security Agency, said that squirrels have been the number-one threat experienced to date by the U.S. electrical grid.

Squirrel-related outages have plagued both urban and rural substations, cutting power to thousands of residences and businesses, and costing utilities hundreds of thousands of dollars in repairs to their facilities and reputations.  

TransGard has discovered a number of factors that make squirrels such a problem for utilities: 

  • Intelligence    Squirrels are smart and capable of remembering solutions to problems for years. They can bypass or outsmart many of the less-effective substation protections. 
  • Basking  In warm weather, squirrels like to stretch out on flat surfaces and warm themselves in the sun.  The elevated areas of substations are tailor-made for this activity. 
  • Warmer weather  A series of mild winters and fewer days of freezing temperatures in the U.S. have reduced typical animal mortality, thus increasing the number of squirrels in their respective habitats. In addition, warmer weather brings squirrels out and in search of food sooner, which results in earlier incursions into electrical substations.
  • Instinctive behavior    Squirrels seek out trees or other vertical structures to climb when they feel threatened. Substation equipment, poles and chain-link fencing appeal to squirrels, which instinctively seek height for protection. 
  • Shrinking habitat  A 2014 study published by Wildlife Society Bulletin found that increased residential and business development has pushed animal habitats toward substations that were initially placed in areas with limited animal activity. The shrinking animal habitat, a phenomenon which continues to accelerate, increases the likelihood of substation incursion by squirrels.

Squirrels aren’t just smart, they’re persistent.  Engineers and technicians have attempted to prevent or discourage squirrel incursions by using an array of methods: bushing guards, heat shrink tapes and tubing, screening, repellants, greases, pole covers, lights, insulator coatings, and more. These measures have had some temporary success, but they haven’t provided permanent solutions. 

What TransGard has learned is that using a squirrel’s intelligence and instincts can help provide a deterrence. TransGard fences deliver a humane shock to animals that attempt to climb the fence, and not only does the experience of a shock deter immediate action, but a squirrel’s “spatial memory” of an unpleasant experience also informs future behavior, encouraging them to avoid substations altogether. 

The TransGard lesson of “an unpleasant experience” has proven successful on multiple species of climbing animals, and has helped solve the challenges of squirrels at many of the  3,000 substations at which TransGard fences have been installed across the United States.  For more information, visit or call TransGard at (717) 900 6140.

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