Abstract

Sleep is a foundational biological need with direct implications for canine welfare and behaviour, yet it is often under-assessed in practice. This literature review synthesises current evidence on sleep architecture and regulation in dogs, and translates key findings for behaviour professionals. Dogs are polyphasic sleepers who cycle through slow-wave sleep and rapid eye movement (REM) more frequently than humans; adult dogs typically spend a modest proportion of total sleep in REM, with puppies showing proportionally longer REM as they consolidate learning. Neurobiological regulation involves circadian timing, melatonin signalling, homeostatic sleep drive, and interacting arousal-sleep systems, while household routines and environmental stimuli shape sleep continuity and quality. Across studies, insufficient or fragmented sleep is associated with lower frustration tolerance, heightened reactivity and anxiety, reduced reward sensitivity, and slower progress in behaviour change. Two applied domains are highlighted: puppies, for whom sleep supports self-regulation and reduces common concerns (mouthing, inability to settle, destructive behaviours); and anxious or reactive dogs, where “activity breaks,” trigger reduction, and optimised sleep environments can interrupt stress-sleep feedback loops. Practical recommendations include routine sleep history and monitoring, provision of quiet choice-rich rest areas, structured low-arousal pre-sleep activities, and consideration of co-sleeping preferences where appropriate. When external stressors or comorbidities impair sleep, veterinary collaboration—including discussion of behavioural medication—may be warranted. Limitations of the evidence base (e.g., reliance on owner-reported measures) and priorities for standardised assessment are noted. Integrating sleep into case formulation is likely to improve outcomes for dogs and caregivers alike.

Introduction

Researchers, caregivers, and professionals all often wonder what dogs are dreaming of when their legs start moving whilst they sleep. Whether they are chasing rabbits or running on the beach, it is no doubt that they appear to be entirely in a world of their own. But sleep is not only a way to escape the stressors of day-to-day life. It is also an essential part of homeostasis and can have a large impact on the physical and behavioural health of an individual.

When considering a holistic approach to behaviour and training concerns, sleep is often under-investigated. The hierarchy of a dog’s needs (Kinsman et al., 2020), identifies biological needs as the first level of behavioural well-being, with changes in the pattern and duration of sleep often reflecting a dog’s experience whilst awake, including how comfortable they are in their own environment (Michaels, 2022). Sleep will naturally vary between individuals, and is also impacted by age, health, lifestyle, and other external factors. The sleep cycle in most mammals, including dogs, consists of slow wave sleep followed by rapid eye movement sleep and then wakefulness (Owczarczak-Garstecka & Burman, 2016).  Dogs experience sleep cycles that are like humans’, but they progress through these cycles more quickly. While humans typically go through four or five cycles, dogs can complete 20 or more (demonstrated in figure 2 below). The first sleep cycle occurs in a light sleep, characterized by deep and rhythmic breathing.

Dogs enter rapid eye movement (REM), the second cycle of sleep, approximately 10 minutes after beginning light sleep. In this phase, you may observe your dog twitching or lightly barking during their nap, which suggests they are dreaming, although this doesn’t indicate the quality or experience of the dream if it’s occurring (i.e., it is not necessarily a good or a bad dream).

The dog’s brain remains active during REM sleep, exhibiting irregular and uneven brain waves similar to those when they are fully awake. Signs you might notice during the REM sleep phase include:

• Eye movement
• Facial muscle twitching
• Whining
• Soft barking
• Sleep “running” behaviour

Research has shown that during REM sleep, dogs exhibit brain activity in the same areas associated with hunting and chasing prey, indicating that the running behaviour may be linked to dreams of pursuing rabbits or small animals. Dogs typically spend about 10% of their sleep time in the REM cycle, and puppies often experience longer durations in REM sleep as they learn about their environment and process new information while they sleep.

The physiological pathway of sleep in dogs shares similarities with that of humans, but also has unique aspects specific to canine biology.

Circadian Rhythm

Like humans, dogs have an internal biological clock regulated by the suprachiasmatic nucleus (SCN) in the hypothalamus. This circadian rhythm helps to synchronize sleep-wake cycles with the natural light-dark cycle, influencing when dogs feel sleepy or alert.

1. 1. Melatonin production: The pineal gland in dogs secretes melatonin in response to darkness, promoting sleepiness. This hormone helps signal the onset of night and facilitates the transition into sleep.
   2. Arousal and sleep-promoting systems:
      • Arousal systems: Areas in the brainstem, such as the locus coeruleus and raphe nuclei, release neurotransmitters like norepinephrine and serotonin to maintain wakefulness and alertness.
      • Sleep-promoting systems: The ventrolateral preoptic nucleus in the hypothalamus promotes sleep by inhibiting the arousal systems. It releases neurotransmitters such as gamma-aminobutyric acid (GABA) and galanin, which help induce sleep.
        

        Figure 1. Sleep-wake regulation Note: VLPO = ventrolateral preoptic nucleus; GABA = gamma-aminobutyric acid; REM = rapid eye movement; SWS = slow-wave sleep; EEG = electroencephalogram. This figure shows the distinct roles of four critical brain structures involved in the control of sleep and wakefulness (Owens et al., 2013).

         

   3. Homeostatic sleep drive: The longer a dog is awake, the greater the drive for sleep becomes, similar to humans. The accumulation of adenosine, a neurotransmitter, increases sleepiness and promotes the need for rest.
   4. Neurotransmitters: Various neurotransmitters are involved in regulating sleep in dogs:]>
      • GABA: An inhibitory neurotransmitter that promotes sleep and relaxation.
      • Acetylcholine: Plays a role in facilitating REM sleep.
      • Histamine and orexin: Neurotransmitters that promote wakefulness and alertness.
   5. Environmental factors: Dogs are influenced by external factors, such as their environment and routine. They may sleep more during the day if their caregivers have a consistent schedule, aligning their sleep patterns with human activities.

This physiological pathway ensures that dogs can effectively regulate their sleep cycles, allowing them to achieve the restorative sleep necessary for their overall health and well-being.

Unlike humans, dogs are polyphasic sleepers, meaning that they sleep on and off during the day rather than experiencing one large period of sleep overnight. The amount of sleep dogs should get is a debated topic, with the most common suggested amount being between 12 and 14 hours. The average amount of sleep reported in the literature appears to be between 26-31% of the daytime (Adams & Johnson, 1993; Owczarczak-Garstecka & Burman, 2016; Zanghi et al., 2012) and 60-70% of the night (Owczarczak-Garstecka. & Burman, 2016; Zanghi et al., 2012).

Although there is no conclusive amount of sleep suggested for dogs, one thing that is widely agreed on across both the literature and professionals is that lack of sleep has a negative impact on welfare. Reported effects include worsening responses to negative stimuli, anxiety, aggression (Banks & Dinges, 2007) reduced sensitivity to rewards (Willner et al. 1992), lower frustration tolerance (Kamphuis at al., 2012), and reduced ability to cope with stressful situations (Vandekerckhove & Cluydts, 2010). This ultimately can be translated to difficulties in managing behaviour, worsening of behaviours of concern, and lack of progress with training and behaviour modification.

Whilst a holistic approach should be taken with all behaviour queries, there are two main areas where particular attention should be paid to the amount of sleep the dog is getting, and where active sleep strategies may improve the prognosis of the behaviour.

Figure 2. Typical hypnogram of three-hour-long sleep recordings of a human and a dog (Reicher et al., 2021)

Sleep in puppies

One of the most highly impacted areas in the development of behaviours of concern, and a logical place to start, is with puppies. Similar to adult dogs, the population norms for dogs under 12 months does not exist. Kinsman et al. (2020) set out to try and fill some of the gaps in knowledge. Data was collected as part of the generation pup study, with information on 2,332 (age 16 week) and 1,091 (age 12 months) puppies collected via online surveys. Caregivers were asked for approximate minimum and maximum hours of sleep during an average 24-hour period, as well as the presence of a range of sleep-related behaviours. The study identified that 16-week-old puppies slept longer than the 12-month-old cohort, which was represented mainly by a decrease in daytime sleep. The mean total hours caregivers reported that their dog slept in a 24hour period was 11.2 hours for 16-week-old puppies and 10.8 hours for 12-month-old dogs. This is slightly longer than a previous study that reported 10.1 hours to be the average sleep time within a 24-hour period. It should be noted that the data presented in this study was owner-reported; whilst this is often one of our only sources for an insight into our dogs’ lives, the data can be unreliable depending on a number of factors, including the instructions given, if the caregivers kept a diary or just tried to remember when they completed the survey, and several other factors.

Most common behaviour and training concerns seen in puppies, such as barking, mouthing, inability to settle, chewing, and other destructive behaviour, are intensified by lack of sleep, often leading to frustration of caregivers, inappropriate handling or potential rehoming of the puppy. As discussed previously, dogs are polyphasic sleepers, which means sleep is often interrupted, particularly during the day where we are more active. This may be a particular concern when considering “lockdown puppies” (dogs raised during periods of COVID-19 lockdowns and movement restrictions), where most of the public were at home during the day, when they previously would have been at work. Puppies often have also not had the ability to learn to self-regulate behaviour and sleep, so caregivers often will need to set the puppy up for success and encourage sleep. Whilst polyphasic sleep may suggest that these regular interruptions fit with the natural sleep pattern, they actually break the cycle by waking the dog outside of their own rhythm.

This can be done by giving the dog a specific quiet area with minimal distractions and stimulation (Bódizs et al., 2020; Schork et al., 2022). This could be in the form of a crate or puppy pen initially, which if utilised correctly has the added benefit of a clear expectation of relaxation and sleep. A study from Tooley and Heath (2022) looked at stimuli that disturb a dog’s sleep, and the associated responses of those dogs. Two clear response types emerged, which were labelled “ease-of-disturbance” which relates to how easy dogs are roused and “wake-and-assess,” where the dog will wake up and then take in information from the environment. Only the former showed a significant effect on dogs with undesirable behaviours. Dogs with a high ease-of-disturbance score would react to both social stimuli (caregiver entering or leaving the room the dog is sleeping in) and environmental stimuli (a noise external to the house that is easily heard by the caregiver). Dogs with a low score within this factor would remain asleep during exposure to both social and environmental stimuli. A greater ease-of-disturbance score correlated with increased undesirable behaviours, which supports the importance of sleep as part of a holistic approach.

Within the same study, 27.5% of dogs slept in the same room as owners and 37% of dogs would usually make that choice  (Tooley & Heath, 2022). Similarly, Kinsman et al. (2020) found that 59% of dogs given the same choice chose to sleep “close to people.” Guardians should be encouraged to have a set routine whenever possible, where the puppy is provided with some low-arousal and calming activities such as snuffle mats, chews, and other enrichment that can help to start the sleep schedule. It would also be sensible to start to introduce these activities and expectation of sleep after arousing activities such as walks or play time to help the pup learn to manage arousal and not perform undesirable behaviours because they are not able to calm down. Co-sleeping with dogs, however, is often highly debated, particularly when considering the outdated dominance theories and other inaccurate models. The paper discussed above would suggest co-sleeping may be beneficial to improving the quality of dogs’ sleep, as well as guardians’. One study that examined both dog and cat caregivers found that participants who co-slept with dogs reported greater comfort and security than those who co-slept with cats or humans and less nighttime disturbance than those who co-slept with humans (Schork et al., 2022).

Night times can also be a struggle for new puppies and caregivers. This again should have a consistent routine where the dog is calmly taken out to eliminate, and then brought back in and encouraged into their sleep area. Initially there may be a benefit to having the puppy’s sleep area near the caregivers’ own bed to help settle the puppy. It can then gradually be moved farther away as the puppy grows in confidence. It is perfectly normal for the puppy to be restless or whine for the first few nights, and leaving them to self-settle may be appropriate unless they are showing clear distress or unable to settle after a few minutes. If they are struggling to settle, then caregivers may want to consider where the sleep area is located, they may try to take the puppy back out to eliminate, or look at adding comforting elements such as a hot water bottle wrapped in a blanket. There is also a lot of debate about the benefits of co-sleeping for both the dog and humans, with little evidence of this having a negative effect (Hoffman, Stutz & Vasilopoulos, 2018). However, professionals may need to discuss this with the caregiver to ensure it fits well with their lifestyle. Feeding time may also need to be considered, with the puppy eating a couple of hours before bed.

Sleep for anxious or nervous dogs

The second area where sleep is particularly important is in dogs who have anxiety issues such as reactivity (lunging, barking, growling, and snapping) to dogs, people, or other stimuli on walks. Regular exposure to triggers increases stress, which can affect the amount and quality of sleep, and as discussed earlier, this affects the dog’s ability to cope with exposure to triggers. Thus, we enter a circle of negative emotions and lack of sleep (Schork et al., 2022; Vandekerckhove & Cluydts, 2010; Banks & Dinges, 2007; Kamphuis et al., 2012). The first piece of advice is always to avoid triggers to prevent the dog from practicing the problem behaviours and reduce their stress. This is not always possible, and in cases where exposure to triggers is affecting the dogs sleep schedule, we may want to consider activity breaks, where the dog may miss a day of walking to reduce exposure to triggers and allow the dog to recover. These breaks can be helpful, but we need to remind caregivers to engage in alternative activities in the home that are appropriate to the individual dog, with guidance as needed.

Caregivers may also need to set up areas to encourage good rest, thinking about things like various bedding options, allowing the dog to choose between curling up and lying completely stretched out, different heights of bedding, and beds in a quiet area, particularly if the household is busy. In some cases, where external stressors are greatly impeding sleep, then we may need to consider other ways of reducing stress and anxiety, including behavioural medication. Any concerns around sleep should be discussed with a veterinary professional who can refer to the appropriate professional as needed.

It is clear from both the literature and real-world evidence that sleep is an extremely important part of a dog’s life and should be included in all holistic approaches to problem behaviours and welfare. Increasing sleep improves quality of life for both dogs and their caregivers. Setting the dog up for success by providing appropriate sleeping environments can be the key to ensuring excellent quality and quantity of sleep, which is part of a holistic approach to dog guardianship, in particular supporting our clients as they address undesirable behaviours in their pets.

References

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