Can Dogs Sense an Intruder?

No matter the size or breed, dogs have been making us feel secure for centuries. Dogs know what is going on around us before we do sometimes, alerting us to things like seizures and natural disasters. Some dog owners can even hear the difference in Fido’s bark when greeting someone they know and those they do not. They know it is us when we come home, greeting us with a wagging tail and kind eyes.  

But how is it that they are able to distinguish their people from the unknown intruder? Is it our scent, our heartbeat, or the sound, specifically, of our keys? In this article, we investigate if and how dogs can sense an intruder.

When a dog detects someone they are not expecting entering their domain, they can exhibit a number of different body language signs depending on the animal’s degree of aggression. The most common signs to look for, even in the most docile of pups, are barking and a general sense of alertness.  

While it is difficult to deduce from barking alone whether a dog can sense an intruder or not, it is often an indicator that they are trying to tell you something. If your dog is a little more feisty, they may growl, along with other subtle signs of a discomfort and ire. In contrast, if your dog is on the submissive side, he or she might start whining because an intruder is scaring them or causing them anxiety. Either way, it is likely that an intruder will cause a degree of vocalization from the animal.

Reading body language and knowing your dog’s different sort of barks can be a life-saving skill, especially in instances of home invasion by an intruder. Being able to distinguish a dog’s poor manners from a reaction to protective instinct is challenging to even the most proficient of dog trainers. Often, it just takes time for owners to become attuned to the differences in body language demonstrated for intruders as opposed to familiar faces.

Dogs were domesticated for several practical purposes - hunting, service, and guardianship. Dogs have been used as guardians of people and places since before history was written. 

Surely, the signs stating “Beware of Dog” are not always for show. Several breeds have been specifically identified as particularly skilled in identifying intruders like the Doberman or the Cane Corso. Even still, it is suggested that all dogs have a sense of territoriality that translates into their ability to sense incoming intruders. This sense of ‘familiar versus other’ has been used advantageously in dogs that monitor border perimeters or police dogs used to seek out suspects in places they ought not to be.

New articles have covered stories of heroic dogs protecting their families from home invasions and burglaries using their keen senses. For example, the story of Murin, a German Shepherd in Richmond, Virginia, was plastered all over Facebook for weeks. The morbid aftermath of Murin’s brave defense of his people’s home went viral, further reinforcing the idea that dogs can sense an intruder.  

And while the question of whether dogs can sense intruders or not seems all but answered, we might be better served to ask ourselves how, as we think critically about training dogs to indicate the presence of an intruder.

There are several scientific observations to be made in the explanation of how dogs can sense intruders. The first is a dog’s ability to conceive of what makes the sounds of their people coming home unique, whether that be keys, footsteps, or their voice. By utilizing their ability to hear so clearly, a dog is typically able to establish firm parameters about what the home environment is expected to be like on a day to day basis.

Second, a dog is constantly employing their insanely sharp sense of smell. Dogs are able to identify, with ease, the scent of someone they recognize over the someone they have yet to meet. Even before an individual walks through the door, dogs have been alerted to who it is using their senses of smell and hearing.  

Because dogs are historically pack-animals, they perceive their humans as a part of their pack. When the signals they are sensing do not reflect the entry of a pack member, many dogs go on the offensive in order to feign any intrusion.

To train a dog to alert to an intruder demands months of stringent command over barking. In order to be accurate, a dog must learn to bark only in instances of intrusion to prevent confusion. As with any trick, the dog must be taught what behavior is being lauded, so creating a false intruder scenario would be highly beneficial so long as safety is adequately handled.  

Once you are able to create an intruder situation that is believable for the dog, be sure to reward any behavior indicating alertness or barking. Positive reinforcement is absolutely critical in training a dog to act on a sensing of a ‘foreign entity,’ especially in helping a dog navigate the delicate system of who does and does not belong in their home after being exposed to innumerable people.

One thing that is highly recommended in the training process is to be mindful of overly aggressive behavior. If a dog is exhibiting signs that they may bite any face that is unfamiliar without provocation, such as visiting trades-workers, it is advisable that the animal spend a bit more time getting used to the presence of people in a secure setting. This line between aggression and responsible pet ownership is a fine one to walk, but trainers need to be careful about how quickly those tides can turn.