5 min read

Why Are Some Rescue Animals Aggressive?


Adopting a rescued pet can be a rewarding experience for both pet and new pet parents. While most animals will be excited to find a new furever home, some may have had their ups and downs that have left them unsure of the new changes they are facing. For some, aggression is their way of protecting themselves, but it can usually be overcome with some extra care and attention.  

Whatever their history, it’s important to understand that your new rescue may come with some baggage, but you can help them unload it for a happier, healthier life with you! Let’s take a look at the reasons behind aggression to help you get started. 

Why are some rescue pets aggressive?

Not all rescues are aggressive, and many acan easily adapt to their new family and home. For some, mild antisocial behavior may just be part of the acclimation process. Being reactive to every stimulus, or hiding under the bed are often temporary behaviors as they learn to trust their new humans and environment. With others, though, fear and anxiety from their past experiences can appear as aggression, which can be harder to manage. 

To understand aggressive behaviors, it helps to have information about the history of the rescue, though that may not always be possible. Your new pet may have previously lived a cushy life indoors with a great family, but was given up due to finances, a death, bad behavior or other factors. Or they could have been rescued off the street where resources were limited and predators were a threat. And some very unlucky animals may have endured abuse or neglect. Living through these situations can create issues of abandonment, fear, anger or mistrust, or even PTSD. Like a veteran returning from war, these animals need time, patience and a lot of love to help them navigate their new life and begin to feel safe again.

Aggression can occur due to several factors, and knowing the type of aggression your rescue is exhibiting can give you the tools to help your pet overcome it. Types of aggression include: 

  • Illness or injury – When a dog or cat is in pain or just not feeling well, they might use aggression as a tool to maintain space around themselves. They don’t understand why they’re hurting and may associate the discomfort with you if you approach them. Some illnesses that can cause aggressive behavior include injuries, hyperthyroidism, hypothyroidism, cognitive disabilities, brain tumors, arthritis, or toxoplasmosis.

  • Fear aggression - Animals that have been abused or have lived on the streets for a time may be scared of everything, including you. Their aggression comes from feeling cornered or threatened. For example, if they’ve been slapped on the head before, attempting to pet them by reaching over their head could elicit a growl or worse.

  • Possessive aggression – Guarding what has value to them, like food, is a common cause of aggressive behavior. The thing they value may be their new litter of puppies, or their new family, a toy, or a treat. For some rescues, there may have been few resources to go around where they came from, but having easy access to resources and a little training can often curb this behavior. 

  • Dominance aggression – Dogs and cats are descended from wolves and big cats which keep order by following a strong leader. If a member of the community attempts to gain some control or even usurp the leader, the result can be aggression to show them who’s boss. That same DNA still exists in our pets, and a dominant animal may be behaving aggressively to establish or maintain their dominance.

  • Frustration aggression – When a dog or cat wants something, but is restrained by a leash,chain, window, or cage, they may become frustrated. For the unlucky human or animal whom they encounter next, the resulting snarl or bite may be redirected aggression to express that frustration. 

Recognizing the cause of your rescue’s aggression is the first step to helping your furry pal adjust to their new life. Along with veterinary medical care and training, techniques such as trigger avoidance, desensitization, and reassurance can give you both the tools to succeed and live a happy life together.

Multi-colored cat hiding underneath a couch - why are some rescue animals aggressive

What are the signs of aggression?

Rescued animals tend to produce signs of aggression that correspond to their level of fear, frustration, anxiety, or resource possessiveness.

Typical signs of aggression in dogs include:

  • A still, rigid body
  • Growls or snarls
  • Bared teeth
  • Lunging
  • Nipping or mouthing
  • Nudging aggressively with their nose
  • Whale eye (whites of eyes showing)
  • Turning the head away and refusing eye contact
  • Rapid tail wagging
  • Lip licking or yawning
  • Raised fur on the back and tail

In cats, the signs of aggression may be more subtle, including:

  • Upright position with stiff straight legs
  • Raised rear end 
  • Tail stiff and lowered or rapidly flicking
  • Direct stare
  • Upright, slightly rotated ears
  • Raised hackles
  • Constricted pupils
  • Movement forward while directly facing
  • Growling, howling, or yowling

Short of actually biting or scratching, most of these signs are warnings. Recognizing them may help to avoid a confrontation.

Happy rescue dog and cat cuddling with family

Tips for managing aggression in your pet

While an aggressive outburst can catch you off guard, whenever bringing a new pet home, rescued or otherwise, you should always be on the lookout for behavioral signs and cues. There are also some things you can do to prevent or defuse an attack by your dog or cat. How you position your body and your facial expressions, and how you approach an animal who is showing signs of anxiety or fear aggression can help them to learn you are not a threat. 

Always remember to never yell at or punish a dog or cat who is being aggressive, as this will only prove to them that they should be afraid of you. Instead, here are some tips to help you keep your rescue calm and learn to trust you:

  • Remain calm

  • Allow the dog to approach you 

  • If you approach the dog, do so sidewise with your head turned so you’re not making direct eye contact

  • Keep your arms at your sides and let your hands hang loosely

  • Use high-value treats for positive reinforcement if they sit, lie down, or approach calmly

  • Don’t attempt to pet them, which may only agitate them

  • Be prepared to stand or sit with them for some time to let them decide whether to retreat or come to you for reassurance 

  • Allow them to enter their safe space if they wish, i.e., a crate, a room, or behind the couch

  • Don’t push or try to control them or their behavior unless you or someone else is in imminent danger

  • Watch your pet to learn how to recognize their aggression triggers and signs, and book an in-home training session to learn the best ways to address signs of aggression in your rescue pet

Just as not every dog or cat should be expected to act aggressively, not all rescued dogs and cats will be a “problem child.” If you meet them on their terms and slowly work towards alleviating the cause of the aggression, you will go a long way to helping them adapt and become pawrfect pets.

Got more questions about your pet’s aggressive behavior? Chat with a vet expert to get answers about your pet’s quirks, health, and more!

Comments (2)

caroline natalia


useful informations thank you , https://www.google.com/



I have recently rescued 2 small breed senior dogs, they were surrender together, so I wanted to keep them together. One dog is showing sign of protective agreement towards other little guy.( which is a little sweet pea).He shows teeth & growls.

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