When behaviour changes feel sudden
Behavioural changes in our dogs often take us by surprise. Everything seems fine, until one day your previously affectionate companion snaps when you reach out to stroke them. Shock, embarrassment, anger, even guilt can follow. Many owners then reach out to a dog trainer or behaviourist, hoping to have the unwanted behaviour “fixed”.
But what is causing it?
Sudden or escalating behaviour changes always raise an important question: could pain be involved? And while there could be many possible reasons for a behaviour change, pain is one of the most significant – and one of the easiest to miss.
Why pain must be ruled out first
If pain is an underlying factor, behaviour modification alone is unlikely to be effective.
Appropriate pain management doesn’t automatically erase learnt behaviours, but without it, meaningful behaviour change is often impossible. A dog cannot learn new coping strategies if they are physically uncomfortable, distressed, or constantly managing pain. This is why a vet check should always be the first step when behaviour changes appear or intensify.
How easy is it to spot signs of pain in our dogs?
Many owners expect pain to look like:
- Limping
- Reduced mobility
- Crying or yelping
- Flinching when touched
Even the example we gave at the beginning was quite “obvious”. But in reality dogs are remarkably good at masking pain and discomfort. A dog in pain may still run, jump, chase, play enthusiastically, and have zoomies. In many cases the signs are often subtle and appear long before the dog’s behaviour changes.
When more obvious physical signs are absent, pain may show up through changes in behaviour, including:
- Restlessness or difficulty settling
- Early waking or disrupted sleep
- Excessive licking and coat changes
- Reduced frustration tolerance
- Heightened reactivity or irritability
- Reduced ability to self-regulate
- Increased anxiety
Pain can also amplify existing emotional or motivational states. A dog who was already a little anxious, reactive, or sensitive may appear to “suddenly worsen” – when in reality, their capacity to cope has been compromised.
According to CAM (Canine Arthritis Management) “Dogs express pain in many subtle ways, which we often identify and associate with the disease late in its course. Please don’t delay seeking veterinary advice, waiting until your dog limps or yelps to confirm your suspicions of pain, as by then they are likely to be in significant pain. ” (4)
So what else do we often miss?
Mouthing, destruction and displacement behaviours
Some dogs show increased mouthing, chewing or destructive behaviours when in pain. These behaviours are not attempts to be “naughty” or controlling. They often function as displacement or tension-reducing behaviours – or ways of reducing internal discomfort (1; 10). The feeling of relief that follows can be reinforcing, even though the original cause (pain) remains unresolved.
Guarding spaces: comfort becomes valuable
Has your dog suddenly started guarding the sofa, bed, or specific resting spots?
Soft, supportive surfaces can become especially valuable to dogs experiencing discomfort. These areas may offer relief, warmth, or the ability to rest in a position that minimises pain.
Guarding in these contexts could be suggest underlying pain and protecting comfort, not dominance or status.
Chronic pain and emotional wellbeing
Pain, when unnoticed or left undiagnosed and untreated for long time, can become chronic. Chronic musculoskeletal pain, even when mild, can affect day to day life significantly. Over time, persistent discomfort can:
- reduce stress tolerance
- lower arousal thresholds
- increase anxiety and reactivity (8)
- lead to chronic stress (15).
Chronic pain doesn’t just affect behaviour in specific situations; it influences the dog’s overall emotional state, behavioural expression and well-being (6; 8).
Pain, handling and defensive behaviour
Pain and chronic medical conditions can make physical handling uncomfortable or painful, which could be a factor in any defensive reactions (12). This may affect stroking, lifting, grooming, claw clipping, putting harness on, etc. If snapping, growling or avoidance have previously succeeded in stopping or preventing the interaction, and therefore removing the pain (2), and providing relief (14), those behaviours are likely to be repeated, they become learned behaviours.
With chronic pain or mobility issues, grooming can be especially challenging (3; 5).
- Handling one paw even before the actual claw clipping may be uncomfortable due to joint stiffness or altered weight distribution
- Brushing over tense or sore areas may cause pain, even with gentle pressure
Over time, grooming tools — and the people holding them — can start predicting discomfort and pain (13), and what looks like “overreaction” is often a learned response based on pain history.
And from the dog’s perspective, the behaviour works.
Seasonal flare-ups and environmental stressors
Chronic pain conditions, particularly those affecting joints, often worsen in colder weather (11). Autumn and winter can bring increased stiffness, greater discomfort and seasonal pain flare-ups, making dogs more irritable, potentially increasing stress levels (8) and lowering his threshold for reactivity and aggression.
At the same time, environmental stressors such as storms, wind, fireworks, and shorter daylight hours could also lead to low mood and pessimistic bias, making any other underlying issues worse (9). Even dogs without noise sensitivities may be startled by sudden sounds like thunders or fireworks, leading to abrupt movements that trigger pain (7). This combination can lower tolerance and increase the likelihood of reactive or defensive behaviour.
The takeaway
Behaviour doesn’t happen in isolation.
When we see behavioural changes, especially sudden or escalating, pain should always be part of the conversation — not an afterthought.
Effective behaviour work starts with:
- Veterinary assessment and appropriate pain management where needed;
- Adjusted expectations and management strategies;
- Behaviour modification that considers both the dog’s physical and emotional capacity.
Pain often explains behaviour. And understanding that explanation is what allows us to support our dogs more fairly, compassionately, and effectively.
REFERENCES:
(1) Arhant, Christine; Winkelmann, Rebecca; Troxler, Josef (2021) Chewing behaviour in dogs – A survey-based exploratory study. Applied Animal Behaviour Science 241, 105372.
(2) Beaver, Bonnie V. (2009) Canine Behaviour, Insights and Answers, Second Edition.
St Louis, Missouri, Saunders Elsevier.
(3) Bekoff, Marc (2022) Grooming Dogs: What’s Good and Bad From Their Point of
View, Psychology Today.
(4) Canine Arthritis Management (2026) Does my dog have arthritis? https://caninearthritis.co.uk/what-is-arthritis/identifying-the-signs/
(5) Edwards, Petra T.; Hazel, Susan J.; Browne, Matthew; Serpell, James A.; McArthur,
Michelle L.; Smith, Bradley P. (2019) Investigating risk factors that predict a dog’s fear
during veterinary consultations. PLoS ONE 14(7): e0215416.
(6) Malkani, Rachel; Paramasivam, Sharmini; Wolfensohn, Sarah (2024) How does chronic
pain impact the lives of dogs: an investigation of factors that are associated with pain using
the Animal Welfare Assessment Grid. Frontiers in Veterinary Science 11:1374858.
(7) Meneses, Tia; Robinson, Jessica; Rose, Jessica; Vernick, Jennifer; Overall, Karen L.
(2021) Development of and pharmacological treatment options and future research
opportunities for separation anxiety in dogs Journal of the American Veterinary
Medical Association, 259(10), 1130-1139.
(8) Mills D S; Demontigny-Bédard I; Gruen M; Klinck M P; McPeake K J; Barcelos A M;
Hewison L; Van Haevermaet H; Denenberg S; Hauser H; Koch C; Ballantyne K;
Wilson C; Mathkari C V; Pounder J; Garcia E; Darder P; Fatjó J; Levine E; (2020)
Pain and Problem Behaviour in Cats and Dogs Animals 10(2), 318.
(9) Mills, Daniel; Dube, Maya B.; Zulch, Helen (2013) Stress and Pheromonatherapy in
Small Animal Clinical Behaviour. UK, John Wiley & Sons, LTD.
(10) O’Heare, James (2007) Dog Aggression Workbook. Ottawa, Canada, BehaveTech
Publishing.
(11) Overall, Karen L. (2013) Manual of Clinical Behavioural Medicine for Dogs and Cats,
St. Louis, MO, USA, Elsevier Mosby.
(12) Reisner, Ilana R.; Houpt, Katherine A.; Shofer, Frances S. (2005) National survey of
owner directed aggression in English Springer Spaniels Journal of the American
Veterinary Medical Association, 227(10), 1594-1603.
(13) Rooney, Nicola J.; Clark, Corinna C.A.; Casey, Rachel A. (2016) Minimizing fear and
anxiety in working dogs: A review Journal of Veterinary Behavior, 16, 53-64.
(14) Sapolsky, Robert (2017) Behave: The Biology of Humans at Our Best and Worst
London, UK, Vintage.
(15) Scholz, Martina; von Reinhardt, Clarissa (2007) Stress in Dogs Wenatchee, Washington,
USA, Dogwise Publishing.