Aggressive at Night in Dogs

Veterinary reviewed by: Michele K.

Why is my dog aggressive at night?

Veterinary reviewed by: Michele K.

Why is my dog aggressive at night?

What is Aggressive at Night?

Aggression can be unnerving for any dog owner, regardless of the time of day. Barking, lunging, growling, and biting can become intense and scary if your dog becomes nervous. But if your dog becomes more aggressive when the sun goes down, it may be a sign that something may be wrong. Even peaceful and loving dogs can have issues that can cause nighttime aggression, even towards family that they are very familiar with. Keeping a record of the incidences of aggression, along with any activities or triggers that may have caused them, can help both you and your veterinarian determine why this might be happening. Reasons can include: 

  • Anxiety 
  • Protection aggression
  • Serotonin 
  • Vision loss
  • Hearing loss 
  • Cognitive dysfunction 
  • Medication

Why Aggressive at Night Occurs in Dogs

Your dog may be exhibiting aggression at night due to various conditions.

Anxiety 

Anxiety can come in many forms. Fears and phobias can result from a traumatic event or situation that your dog remembers and may associate with nighttime, darkness, or even with something that occurs in your particular household in the evening. If your dog shows signs of anxious and nervous behavior at night, he may be afraid of something, and may lash out aggressively to unknowing family members. 

Protection Aggression

Protection aggression is a territorial behavior, and is often shown towards people or animals that are viewed as a threat to the property. It may be that your dog is more nervous at night, or that due to the quiet, he hears perceived threats more easily. Your dog may be on alert for predators, a real fear in the wild, or may be trying to do his duty and protect his family. 

Serotonin 

Serotonin is a neurotransmitter that helps to regulate emotions and the sleep cycle. If serotonin levels are abnormal, it can disrupt and even reverse the sleep-wake cycle, causing your dog to more awake and alert during the night. If you’ve noticed your dog sleeping more during the day, and completely awake at night, this may be what’s going on. Certain medications have been implicated in causing an excess of serotonin, which can result in aggressive behaviors, vocalization, muscle twitching, and even seizures.

Vision Loss

Dogs can experience a decrease in eyesight that can lead to blindness due to age, hereditary disorders, infections, or glaucoma. If your dog is having trouble seeing, he may become more anxious at night when it is already harder to see. Signs this may be an issue for your dog can include confusion in new or changed environments, clumsiness, disorientation, and bumping into objects. He may also have certain telltale signs that are visible in his eyes, such as squinting, tearing, reddened eyes, a weak blink response, and light avoidance. 

Hearing Loss 

Your canine companion can also experience partial or total hearing loss than can be temporary or permanent. This can also occur from age, or from an infection, waxy build-up, inflammation, tumor, or obstruction by a foreign object. A clear sign that your dog is experiencing a loss of hearing is a lack of response to his name, commands, clapping, or other noises. He may not even hear you enter the room, which can cause anxiousness or aggression if startled. 

Cognitive Dysfunction

As dogs age, they can develop dementia or cognitive dysfunction. This can affect everything from when your dog sleeps, to recognizing people or his environment. His sleep cycles may become disrupted, he may become lost in the house, and he may become increasingly nervous or on alert. Aggression during these periods is a signal that your dog is confused and possibly scared. Signs your dog may be experiencing cognitive dysfunction can also include an increase in vocalization, aimless wandering, staring at a wall or an object for a length of time, disorientation, and changes in appetite and social interactions. 

Medication

Certain prescription medications have the potential to cause aggression, serotonin syndrome, or even seizures in dogs. Most of these medications are generally prescribed for behavioral issues, such as antidepressants, antipsychotics, and MAOIs. Other drugs include certain appetite stimulants, amphetamines, opioid painkillers, antivirals, cough suppressants, and drugs prescribed for Parkinson’s disease.

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What to do if your Dog is Aggressive at Night

The best thing to do if your dog becomes more aggressive at night is to note any and all stimulus around him that may be causing or triggering the behavior. Alert your veterinarian to these observations, as well as to any other signs you might have seen in your dog. Accurately describe his eating and sleeping patterns, and any history of medications that he has been prescribed or may have accidentally ingested.  

Your veterinarian will want to determine if there is a physical reason behind the behavior. A physical exam will be performed, complete with hearing, vision, and neurological testing. This can reveal any sight, hearing, or cognitive issues. Bloodwork, a urinalysis, and a fecal test may be helpful in determining any infections, as well give a picture of your dog’s overall health. They can also point to a possible case of serotonin syndrome. X-rays may help to locate an obstruction or tumor. If there is not a physical reason found, then your veterinarian will look at anxiety or aggression as behaviors to be treated.

Medical issues will be treated accordingly. Drug and dietary therapy may help to ease the signs of cognitive dysfunction. Any obstructions, wax build-ups, or tumors in the ear canal might be surgically removed to treat hearing loss that is not permanent. Infections can often be treated with antibiotics.  Serotonin syndrome can be treated by supplementing dietary tryptophan, a precursor of serotonin production. An overdose or negative reaction to medications that may be the cause can be treated if caught early enough. Activated charcoal can help to prevent absorption in the digestive system, and vomiting may be induced. Fluid therapy and drugs may be prescribed to control the resulting signs of an overdose. 

You may need to engage in behavioral training techniques to manage anxiety, aggression, and a change in sleep cycles in your dog. Increasing joyful activities, such as walks and playtimes, can give him the exercise he needs to be able to rest at night. Creating a nighttime routine can help to train your dog to recognize when it is time to relax. Older pets may need orthopedic beds or a more protected sleeping spot to minimize discomfort and the element of surprise by an unwitting family member. For those dogs with cognitive dysfunction, hearing or vision loss, be sure your dog knows you are there with a soft pat or by calling his name. Anxious and aggressive dogs can benefit from desensitizing and counterconditioning techniques to retrain them to be calm during the night.

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Prevention of Aggressive at Night

Prevent anxious and aggressive behavior through socialization and positive training in your dog’s early years. It may not always be possible to predict a fear, but knowing your dog’s trigger can help you to prevent it from occurring, remove your dog from the situation, or retrain him.  

Regular check-ups can reveal the presence of many types of conditions, including eye and hearing loss, infections, and imbalances in the body that can lead to conditions such as serotonin syndrome. Feeding a healthy, appropriate diet can ensure that your dog is receiving all the nutrients he needs to maintain a healthy body.

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Cost of Aggressive at Night

Treatments for nighttime aggression can vary considerably, and will depend on the reason your dog is exhibiting this behavior.  Overall, costs can range from $200 to $3500. While hearing loss and glaucoma can average $350 to $900 respectively, a more complicated issue such as serotonin syndrome can cost around $2400. Aggression can be a difficult condition to treat, and can average $575.

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Aggressive at Night Questions and Advice from Veterinary Professionals

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Rat Terrier

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Two Years

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19 found helpful

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19 found helpful

Has Symptoms

Aggression

Oliver is a rat terrier/russell type terrier. he was rescued/adopted at 3 months old and was quickly introduced to my other 3 dogs. When he is sleeping, he gets aggressive, snarls and bites the other dogs when they go anywhere near him. He now has started attacking them when he hears them licking themselves or each other near him while he's sleeping. Concerned its going to get worse, the other dogs are all 20lbs or less, Oliver is 35lbs.

Jan. 26, 2021

Owner

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Dr. Linda S. MVB MRCVS

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19 Recommendations

Hello, you are through to Dr Linda. I'm very sorry to hear about this issue. Many dogs dislike being disturbed when asleep as they feel vulnerable. I would strongly recommend having him sleep somewhere safe he cannot be disturbed such as a crate. Ensure all dogs have their own safe space as well as their own resources (bed, bowls, toys etc). If they need to share resources, this can lead to conflict. I would also advise a plug in pheromone diffuser such as Adaptil and I would get him started on some calming supplements. He should be checked over by a vet in case of an underlying health issue causing him to be defensive e.g. sore joints or dental disease. If his health check is ok but the issue persists, a behaviourist would be the next option to pursue.

Feb. 15, 2021

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border collie mix

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Three Months

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17 found helpful

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17 found helpful

Has Symptoms

My dog is very relaxed and mostly sleepy during the day. Very sweet for the most part. Around 8 pm he starts getting very hyper and aggressive. I don’t know if he has a ton of energy and thinks he’s playing, but it’s out of character from about 8-10. He bites and lunges and growls at us. He’s 12 weeks old, on no medications, up to date on vaccinations.

Dec. 23, 2020

Owner

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Dr. Linda S. MVB MRCVS

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17 Recommendations

Hi there. This is known as The Witching Hour. Many puppies get the 'zoomies' and become hyper. It is a phase at this age and will pass. Try hard to provide lots of physical and mental stimulation during the day to time your little one out. When being nippy, it is best to re-direct to a tug toy or similar.

Dec. 23, 2020

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