Training & Maintenance

• In order for an underground fence to work a dog has to be properly trained to understand when and why it is receiving a shock. The owner has to be willing to commit time and energy to this training. In addition, maintenance, such as changing the batteries on the collar, will be necessary.
  
  

Perception

• It is not obvious to passers-by that a underground fence exists. People walking by your house will not know that your dog is "contained" and will remain in your yard. This may startle or scare people and other dogs.
  
  

Outside Intruders

• An underground fence does not stop other animals or people from entering your yard. This leaves your dog vulnerable to encounters with other dogs or wild animals, and leaves you liable if your dog bites someone.
  
  

When It's Just Not Enough

• Some dogs may have a high enough pain threshold to not be bothered by the shock. Or a stimulant outside of the boundary may just be too exciting for the dog to be able to resist. While in that instance the dog may be too interested in that squirrel it wants to chase to react to the shock on the way out of the yard, it may then be unwilling to experience the pain to return to the yard.
  
  

Negative Side Effects

• If the shock works as a successful deterrent, a dog may associate it not just with the fence line, but with the entire yard. If it experiences the shock at the same time it is encountering anything else (such as another dog or a person) it can easily learn to associate pain with that encounter, potentially resulting in fear and fear-based aggression. A dog experiencing pain like a shock can engage in redirection, endangering those around it, including other pets and children.