Beyond Herding: Understanding Traffic Chasing in Border Collies

Border collies are consistently over-represented in cases of car chasing, traffic fixation and lunging at moving vehicles (Cooper et al., 2024; Cooper et al., 2025). Typically, the behaviour is often described as hypervigilance and fixation, followed by barking, lunging, spinning, and—if opportunity allows—chasing. This behaviour presents substantial welfare and safety risks, including injury or death of the dog, risk of the handler tripping or bring pulled into the road, and risk of road traffic accidents.

Despite its prevalence, car chasing in Border Collies is frequently explained away as “herding”. While breed-specific motor patterns undoubtedly influence how the behaviour looks, reducing traffic chasing to herding alone oversimplifies a complex, emotionally driven behaviour and risks inappropriate intervention. in this article I’ve taken evidence from ethology, veterinary behavioural medicine, neuroscience, and applied behaviour to outline the primary differentials contributing to car chasing in Border Collies, with particular emphasis on the emotions and motivations behind the behaviour, reinforcement processes, and welfare implications.

Breed selection and motion sensitivity (predisposing factor, not diagnosis)

Border Collies have been selectively bred to perform a modified predatory motor sequence in which orienting, eye, stalking and chase behaviours are exaggerated, while grab-bite and kill behaviours are suppressed (Coppinger & Coppinger, 2001; Case, 2023). This means collies are exceptionally sensitive to movement, able to track and predict trajectories (Völter et al. 2020), and highly motivated to interact with moving stimuli.

Herding trait characterisations describe Border Collies as showing:

• Innate detection of movement
• Intense visual fixation (known as the collie “eye”)
• High impulsivity
• Highly sensitive to sound
• Reactivity to sudden environmental change

These traits make fast-moving traffic a particularly salient stimulus in pet environments. However, motion sensitivity alone does not explain car chasing. Sensitivity to movement is best understood as a predisposing factor that can sometimes be triggered by emotional arousal, fear, frustration, or reinforcement history.

Why traffic chasing is not herding behaviour

For herding to occur, the dog must perceive the stimulus as biologically relevant within a modified predatory sequence. Sheep exhibit biological motion, respond contingently to the dog’s behaviour, have animal odour, and move at speeds the dog can influence. They are clearly prey-like objects.

Vehicles, however, are inanimate, rigid, fast, noisy, non-responsive, do not smell biological and are non-biological in movement.

Research shows that herding breeds excel at tracking and anticipating moving objects on a screen (Völter et al., 2020), but there is no evidence that dogs, or any animals in general, perceive vehicles as livestock. Wild dogs or large African predators have never been reported to misidentify vehicles as prey or attempt to chase them, despite frequent exposure. Durrheim and Leggat (1999), looking at risks to tourists in South Africa over a ten year period, found that, of all the fatalities and non-fatal attacks, all occurred while the tourists were on foot, apart from one non-fatal attack on a vehicle by an elephant. Elephants are herbivores, so this would not have been a predatory attack.

Given the Border Collie’s selective breeding for discrimination and precision, it is implausible that they, of all breeds, would be the most likely to misinterpret traffic as prey.
Clinically, labelling traffic chasing as “herding” risks normalising a behaviour that completely negatively overwhelms collies and poses a substantial welfare risk, and may encourage “outlet” approaches that are unlikely to help reduce or resolve the behaviour.

Differential 1: Fear, startle and threat perception

For many Border Collies, fear and anxiety are central components of traffic chasing behaviour.
Sudden, rapidly approaching (“looming”) stimuli reliably evoke strong fear responses in all animals (King et al., 2003). Vehicles are:

• Large
• Loud
• Fast
• Often appearing suddenly at close proximity
• Sometimes associated with bright lights and splashing water

These properties make traffic a potent fear trigger, particularly when dogs are walked close to the road on a short lead. Physiologically, fear responses in dogs involve sympathetic nervous system activation and endocrine changes including elevated cortisol and stress hormones (Hydbring-Sandberg et al., 2004), priming fight-or-flight behaviour.

But why do vehicles elicit fear in collies more than other breeds?

• Many collies start their lives in sheds or kennels on quiet farms in the countryside so are less likely to have encountered fast traffic before.
• Compared to other breeds they have heightened visual and acoustic sensitivity, and are bred to react to sudden environmental change.
• As a breed, they do not have to be able to tolerate noise, and city living, this wouldn’t be an important trait to shepherds.
• Collies are very impulsive and can react before they think.

I’ve worked with many car chasing collies, and in most individuals, there is a history of either:

• A one-off event in which a loud, looming vehicle drove by very quickly and loudly when the collie was still young, potentially causing one-trial learning.
• A puppy was walked next to busy roads, often to “socialise” them to traffic, and were completely overwhelmed.
• Occasionally a collie will start to car chase during adolescence, often coinciding with a fear period, or development of a musculoskeletal issue

Most collies that car chase initially displayed fearful behaviour prior to the development of lunging at vehicles.
In restrained dogs, flight is unavailable. In Border Collies—historically selected to stand their ground with when moving sheep or cattle, rather than retreat—this often results in explosive “fight/repel” behaviours such as barking, lunging, spinning, and snapping.

Differential 2: Negative affect and breed temperament

Research looking at temperament traits of different dog breeds consistently show Border Collies scoring higher for sensitivity to novelty, impulsivity and negative activation compared to many other breeds (Hammond et al., 2022). Clinically this displays as heightened vigilance, reactivity to sudden environmental changes, rapid increases in arousal, and slower return to baseline arousal.

Many working collies are fearful of sheep during initial exposure, particularly when livestock stand still, stamp or attempt to butt the dog. Dogs that ran away under pressure were useless when working with sheep so would not have been bred from. This has resulted in a population-level tendency to stand their ground under pressure. In modern environments, this predisposition may generalise to traffic contexts, where standing ground replaces avoidance.

Differential 3: Frustration and barrier frustration

Frustration is almost always present in traffic chasing cases. Dogs prone to car chasing are necessarily managed on lead near roads, creating a physical barrier that prevents both approach and avoidance.
McPeake et al. (2021) demonstrated a significant correlation between excessive lunging and barrier frustration. From a neurobiological perspective, frustration is linked to the SEEKING system (Panksepp, 2011), a high-arousal motivational system associated with anticipation and drive. When highly motivated behaviours are blocked, negative affect and arousal increase (Howell & Bennett, 2020), posing a welfare concern when experienced chronically (McPeake et al., 2019).

In traffic contexts, the dog may simultaneously want to move towards the stimulus (chase) and away from it (fear), with both motivations thwarted—creating intense frustration. It’s likely that this frustration behaviour is contributing substantially to the barking and spinning behaviours seen when some collies encounter traffic. It’s this behaviour that makes it impossible to compare the behaviour of collies on lead reacting to vehicles to that of collies herding sheep off-lead.

Differential 4: Predatory motor patterns as emotional regulation (“pseudo-predation”)

Predatory motor patterns are intrinsically rewarding and activate dopamine pathways, which drive feelings of pleasure and reinforces behaviors associated with rewards.. D’Ingeo et al. (2021) argue that predatory behaviours may be recruited during anxiety or frustration because they provide hedonic relief and help the dog to cope in highly arousing contexts.
In Border Collies, where early predatory phases have been selectively exaggerated, orienting, stalking and chasing may be particularly reinforcing. Under stress, these behaviours can function as emotional self-medication, even when the stimulus is not prey-like.

This helps explain why some dogs appear to “enjoy” traffic chasing over time, despite initial fear, and why the behaviour can escalate even in the absence of external rewards. This could also relate to abnormal repetitive behaviours – see below.

Differential 5: Anticipation and arousal priming

Anticipation itself can significantly increase arousal. Anticipation of both rewarding activity and aversive events increase heart rate and stress responses. Studies in working dogs show that anticipation alone significantly alters cortisol, glucose and insulin levels (Angle et al., 2009; Gillette et al., 2006).

For collies that have repeatedly engaged in traffic chasing, anticipation of vehicles may add to an already elevated arousal state, lowering behavioural inhibition and increasing reactivity before the trigger even appears. By the time a vehicle arrives, their arousal is so high that they are completely incapable of regulating themselves, almost like a bottle of pop waiting to go off, with each passing vehicle shaking the bottle then releasing the lid.

Differential 6: Pain and physical discomfort

Pain is an important and often overlooked contributor. Chronic pain is associated with increased impulsivity and reduced emotional regulation (Mills et al., 2020; Mills et al., 2024). Dogs with pain are also more likely to show defensive aggression, which is what we are seeing when collies react to traffic with the “fight” response.

Furthermore, many vehicles are very loud – motorbikes, lorries, buses (with triggering air brakes), rattly trailers and bin lorries are the worst culprits. Collies, as a breed, are very prone to sound sensitivity (Salonen et. al., 2020; Overall et. al., 2016), which has been linked with pain conditions (Lopes Fagundes et al., 2018), and fearful dogs may tense musculature in anticipation of traffic, exacerbating discomfort. Additionally, dogs that car chase often, for their own and their caregivers’ safety, wear head collars, figure of eight collars or harnesses as well as flat collars. Repeated lunging into walking equipment can cause acute pain, further increasing arousal and negative associations with roads, and adding to the “bottle of pop” effect.

Pain should always be considered, particularly in cases with sudden onset, onset at adolescence, escalation, or poor response to behaviour modification alone.

Differential 7: Trigger stacking and cumulative stress

Collies are rarely exposed to one vehicle at a time. It is much more common that they encounter vehicle after vehicle. They are more likely to be able to cope with the first few that they encounter, but repeated exposure to passing vehicles can result in cumulative arousal, often described clinically as “trigger stacking”. Stress hormones persist beyond the triggering event (Overall, 2013), and repeated stressors reduce behavioural inhibition.

Case (2023) describes herding breeds as particularly vulnerable to movement-triggered responses when arousal is high. Once thresholds are lowered, even relatively minor movement can provoke intense chase behaviour, as described in differential 4 above.

Differential 8: Abnormal repetitive or compulsive behaviour

Recent evidence suggests that traffic lunging in Border Collies may, in some cases, meet criteria for abnormal repetitive behaviour (Marin et. al., 2026). Marin et. al.’s study defines lunging as sudden, forceful forward movement towards moving stimuli and identifies key ARB features: escalation over time, generalisation to multiple triggers, persistence despite negative consequences and difficulty disengaging. They also highlighted how it can occur in association with other repetitive behaviours such as light or shadow chasing.

Abnormal repetitive behaviours are stress-related responses often caused by arousal dysregulation, sensitisation and pain, where the behaviour becomes internally reinforcing without resolving emotional distress. Framing the behaviour as herding risks normalising a maladaptive pattern; reframing it as an abnormal repetitive behaviour supports prioritising rehearsal prevention, emotional regulation, and welfare-led intervention.

Neurochemical modulation and response to SSRIs

An important clinical observation in Border Collies presenting with traffic chasing is their frequent and often marked response to selective serotonin reuptake inhibitors (SSRIs), particularly fluoxetine, when prescribed and monitored by a veterinary surgeon or veterinary behaviourists. Anecdotally, I have seen significant reductions in the intensity and frequency of lunging, alongside improved emotional regulation and faster recovery following exposure to traffic-related triggers.

SSRIs can lower baseline arousal, reduce anxiety-driven hypervigilance, and improve impulse control (Overall, 2013). Clinically, this reduction in arousal often allows owners and practitioners to “reach” the dog during moments of rising excitement or stress, where previously the dog was over threshold and unable to respond. High emotional arousal is known to impair learning and cognitive processing (LeDoux, 1996; Overall, 2013), and reducing this arousal can make behaviour modification possible for the first time.

The effectiveness of SSRIs in many car-chasing cases further supports the view that fear, anxiety, and/or abnormal repetitive behaviour processes are core differentials, rather than traffic chasing being a simple expression of herding instinct or prey drive. In particular, fluoxetine’s documented efficacy in reducing compulsive and repetitive behaviours in dogs aligns with the presentation seen in Border Collies whose traffic lunging escalates over time, generalises to multiple triggers, and persists despite negative consequences.

From a neurobiological perspective, SSRIs are understood to modulate serotonergic systems involved in mood regulation, impulsivity, and behavioural inhibition. Their clinical utility in traffic chasing cases is therefore consistent with a model in which arousal dysregulation, emotional conflict, and internally reinforcing motor patterns maintain the behaviour. Medication, where indicated, should always be viewed as an adjunct to careful management and emotion-led behaviour modification, not a standalone solution.

Clinical implications

Car chasing in Border Collies is rarely caused by a single factor. Instead, it reflects the interaction of breed-typical motion sensitivity with an overwhelming array of emotions that leave a collie extremely distressed and completely unable to regulate their arousal. Fear, frustration, conflict, reinforcement, anticipation, and sometimes pain can all simultaneously co-exist and their sense of threat is amplified. Effective intervention requires:

• Rigorous safety management and rehearsal prevention
• Careful behaviour modification
• Careful pacing to avoid flooding
• Veterinary assessment where indicated

Understanding why the behaviour occurs is essential to reducing risk and improving welfare.

References

• Angle, T. C., Gillette, R. L., Welker, K. M., et al. (2009). The effects of anticipation of exercise on plasma cortisol and glucose in sled dogs. Journal of Veterinary Behavior.
• Arons, C. D., & Shoemaker, W. J. (1992). The behavior of collies, huskies, and Shar-Peis toward prey. Applied Animal Behaviour Science.
• Case, L. P. (2023). The Dog: Its Behavior, Nutrition, and Health (3rd ed.). Wiley-Blackwell.
• Cooper, J. J., et al. (2024). Factors associated with vehicle chasing behaviour in dogs.
• Cooper, J. J., et al. (2025). Impulsivity and movement-triggered behaviours in domestic dogs.
• Coppinger, R. and Coppinger, L. (2001) Dogs-A Startling New Understanding of Canine Origin, Behavior & Evolution. Bibliovault OAI Repository, the University of Chicago Press.
• Durrheim, D.N. and Leggat, P.A. (1999) Risk to tourists posed by wild mammals in South Africa. J Travel Med, 6(3), 172-179.
• Gillette, R., Angle, T., Sanders, J. and Degraves, F. (2011) An evaluation of the physiological affects of anticipation, activity arousal and recovery in sprinting Greyhounds. Applied Animal Behaviour Science – APPL ANIM BEHAV SCI, 130, 101-106.
• Hammond, G., et al. (2022). Breed differences in affective states using DIAS and PANAS. Scientific Reports.
• Hydbring-Sandberg, E., et al. (2004). Physiological reactions to fear in dogs. Acta Veterinaria Scandinavica.
• King, T., et al. (2003). Fear responses in dogs to novel and startling stimuli. Applied Animal Behaviour Science.
• Lima, S. L., et al. (2015). Animals’ behavioural responses to vehicles. Biological Reviews.
• Fagundes, A., Hewison, L., McPeake, K., Zulch, H. and Mills, D. (2018) Noise Sensitivities in Dogs: An Exploration of Signs in Dogs with and without Musculoskeletal Pain Using Qualitative Content Analysis. Frontiers in Veterinary Science, 5, 17.
• McGowan, R. T. S., et al. (2014). Positive affect and task success in dogs. PLOS ONE.
• McPeake, K.J., Collins, L.M., Zulch, H. and Mills, D.S. (2021) Behavioural and Physiological Correlates of the Canine Frustration Questionnaire.
• McPeake, K. J., et al. (2021). Barrier frustration and lunging behaviour. Journal of Veterinary Behavior.
• Marin, B., Salden, S., Broeckx, B., Van Den Broeck, W. and Haverbeke, A. (2026) Born to lunge? A survey on lunging behaviour and associated factors in Border Collies. Applied Animal Behaviour Science, 296, 106894.
• 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. and Levine, E. (2020) Pain and Problem Behavior in Cats and Dogs. Animals, 10(2), 318.
• Mills, D.S., Coutts, F.M. and McPeake, K.J. (2024) Behavior Problems Associated with Pain and Paresthesia. Veterinary Clinics of North America: Small Animal Practice, 54(1), 55-69.
• Overall, K. (2014) Behavior Problems of the Dog and Cat, 3rd ed., G. Landsberg, W. Hunthausen, L. Ackerman. Saunders, Elsevier (2013), 472 pp.; $99.95 (paperback), ISBN: 9780702043352. The Veterinary Journal.
• Panksepp, J. (2011). The SEEKING system and motivation.
• Völter, C. J., et al. (2020). Movement tracking and prediction in herding breeds. Animal Cognition.
• Overall, K. L., Dunham, A. E., & Juarbe-Diaz, S. V. (2016). Phenotypic determination of noise reactivity in 3 breeds of working dogs: A cautionary tale of age, breed, behavioral assessment, and genetics. Journal of Veterinary Behavior, 16, 113–125.
• Salonen, M., Sulkama, S., Mikkola, S. et al. Prevalence, comorbidity, and breed differences in canine anxiety in 13,700 Finnish pet dogs. Sci Rep 10, 2962 (2020). https://doi.org/10.1038/s41598-020-59837-z