Dogs Don’t Bite Out Of Nowhere, So Why Did Mine?
Here’s what's really going on
“My dog has never done this before.”
I’m a dog behaviourist and it’s often the first thing people say when they contact me. It makes sense. We tend to think dogs who bite are different from our dogs who sleep with us at night and curl up next to us on the sofa. But the truth is that, under the right (or wrong) circumstances, any dog can bite.
Periods of upheaval, such as the festive period, house moves, a new baby or other sudden changes in routine, can make these incidents more likely. But they can also happen at any point a dog feels pushed past what they can cope with. Most of the time, it happens at home, with people dogs know very well, another factor that often surprises people.
A bite is simply communication. If one happens, it doesn’t mean your dog is going to go around biting everyone and everything at any time. But it does mean it’s sensible to take a moment and think about why it happened so you can reduce the chances of it happening again.
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Read on to find out about the many reasons why a dog can bite and the first practical steps to take if you’ve ended up in this situation.
First, what is a dog bite?
Biting exists on a spectrum. At one end are your warning signs – the last of which is usually a snap where a dog bites the air without actually making contact.
Then there are inhibited bites, where their teeth do make contact but they limit the amount of pressure they use. These bites may bruise but they may not break the skin.
More serious bites, which can cause significant injury and even fatality in really severe cases, are at the other end of the spectrum. They may occur when earlier signals have been missed or ignored, either in that moment or in the past.
This matters because dogs rarely bite ‘out of the blue’. “Sometimes, dogs try and show us lots of other strategies before biting and it can often be a last resort,” says clinical animal behaviourist Helena Woodfieldopens in new tab. “Or, we give the dog ‘no choice’ by forcing them into uncomfortable situations. If we reinforce the early signs of discomfort, we are so much more likely to avoid biting altogether.”
Why do dogs bite?
Fear and anxiety
Much of what people call ‘aggression’ in dogs is rooted in a dog feeling unsafe, uncomfortable and unable to cope. “This is often a fearful or worried response to something they don’t think they can handle in any other way,” says Helena.
When a dog can’t escape a situation, they may resort to biting to make something they feel is threatening stop or go away. These bites can happen with unfamiliar people or during handling, especially in places like the vet clinic where they’re literally backed into a corner. “Sometimes, biting in certain situations can become predictable and learned,” Helena adds. “This is often with repeated exposure to the same stressor.”
Before a fear-based bite, dogs tend to give a series of warning signals. You might notice them freezing, turning their head or body away, showing the whites of their eyes or even growling to ask for space.
Pain and discomfort
Pain is a hugely overlooked reason for dogs biting. Undiagnosed injuries, arthritis, dental disease, stomach issues and more can dramatically lower a dog’s tolerance, making situations they could once tolerate very difficult for them. “Dogs can also have memories of pain,” says Helena. “Therefore may bite to prevent being handled if they feel it could hurt.”
When a dog’s behaviour changes seemingly overnight, pain is the first thing to investigate. It’s not easy to rule out as they’re very good at masking discomfort and some investigations can be costly. And it’s important to remember we can never 100 percent rule it out without being able to speak to them in the same language. But your vet can do their best to see if pain could be a factor in their behaviour.
Frustration and overarousal
Frustration and overarousal can play a big role in a dog choosing to bite. Take situations like if your dog’s getting riled up barking behind a fence or window, is being held back by their lead or getting so excited during play that they tip over the edge. Sometimes when dogs are prevented from reaching something they want, they can redirect a bite onto whoever is closest, even if they weren’t the original target.
These types of bites can be more common in younger or high-energy dogs, who can become easily overaroused and struggle to regulate.
Resource guarding
Resource guarding can overlap with any of the above. However, it deserves a special mention because it can very easily be overlooked. Dogs can guard anything they perceive to be valuable. More commonly, it’s the likes of food and toys. But for some dogs it’s resting spots, random objects and even people.
Resource guarding is a very normal behaviour. If a dog believes something valuable is about to be taken away, they may growl, snap or bite in an attempt to keep it. But as guarding behaviours often start with subtle signs like hovering over an item and tense bodies, they’re easy to miss or dismiss, potentially leading to escalations.
Trigger stacking
Sometimes, dogs don’t bite because of what immediately happened beforehand, but because stress has been building in the background. This is known as trigger stacking. “It can occur quickly or have built up over a period of time,” Helena explains. “For some dogs, when you go back over the last 24–48 hours, you can establish the triggers that would cause them to be in a high state of stress.”
Too much constraint, too much exposure to things they find difficult and too little rest can pile on the pressure, eventually wearing them down. You might need to think about this if you have a particularly busy household or unpredictable routines.
Breed tendencies
Your dog’s breed may play a role when it comes to biting. “For some dogs, it’s a natural instinct to guard and protect a territory,” says Helena. Some people also train their dogs to perform protection and guarding roles, potentially exacerbating the behaviour.
Herding breeds can also have a “strong instinct to chase and bite if they’re in a high state of arousal”, adds Helena.
Simply startled
On some occasions, a bite occurs because a dog simply got startled and reacted instinctively. If your dog ’s in a deep sleep and suddenly woken up by someone trying to hug them, for example, they may be a little disoriented and react before their brain has caught up.
You might notice this more in older dogs whose senses are starting to decline and are therefore more easily startled. But it’s good practice to let all sleeping dogs lie.
What to do immediately after a bite
First, stay as calm as you can and focus on safety. In other words, prevent anything else from happening by creating space and separating everyone safely, especially if there are children around. If anyone is injured, seek medical assistance as soon as possible.
It can feel instinctive to shout at or punish your dog, but this isn’t recommended. “We shouldn’t be shouting at or telling our dogs off for biting,” says Helena. “Biting is often something that happens after lots of other signals are shown and telling our dogs off for showing us those signs means they might stop showing us them.”
Once things have calmed down, Helena recommends gathering information: “Write everything down, what happened 24–48 hours before, then detail what happened just before the bite.” You can then pass this onto a professional behaviourist for advice.
When to get professional help
If your dog has bitten or is showing aggressive behaviour towards people or other animals, it’s best to seek support as early as possible. This is really important, Helena says, as it means “we can catch things earlier and try and work out what’s causing it before they get worse”.
Ensure you find an appropriately qualified behaviourist registered with a reputable body like the Animal Behaviour and Training Councilopens in new tab (ABTC) and who uses ethical, reward-based methods.
