Pet Sort-Out


Why Is My Male Rat Suddenly Aggressive?

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Fancy pet rats undoubtedly make great pets. They love human companionship similar to dogs and keep themselves groomed all day long just like a house cat. These qualities as small pets, make fancy rats globally loved by pet owners.

However, as adorable as these babies are, aggression runs parallelly in their veins. Especially male rats can be very aggressive due to various reasons. 

In this context, if your query is why your male rat suddenly has become aggressive, then I would say that: The reason behind their sudden aggression may sprout from hormonal changes, environmental changes, the influence of other pets, or medical emergencies. It might be a way for them to show you that they are feeling threatened or simply it can be a way to show their dominance.

In this article, we will discuss all the details about sudden aggression in male rats and help you with remedies to stop the situation as well. I encourage all the readers to have a thorough read to acknowledge, understand and help to heal the little pet rat babies.

Signs Of Aggression In Rats

Rats by their biological nature are calm and quiet animals who are happy to explore around silently.  

Rats like all other animals indeed have different personalities from one another. So, chances are some of them are born aggressive. However, as a pet parent, you will understand if your pet rat baby develops a sudden aggressive attitude towards human parents, fellow cage mates, or other family members. 

Here are some prominent signs that you may notice in your rats when they change due to aggression.

  • Quick aggressive biting

 Pet rat biting is encountered by many rat owners. To be specific, rat bites are of different types and thus should be identified correctly. Playful rat bites are soft and hurtless, pet rats can also attempt biting you mistakenly while playing or cuddling. However, aggressive bites come with prior hissing, failed attempts to escape, and are very painful. If you find your male pet rat biting suddenly without any valid foreseen reason, it might be due to aggression.

  • Escaping and hiding during play or cuddle times

Pet fancy rats are cute animals who love to play around with their human parents. They love cuddle hours and will actively climb on you to explore and play. However, if you find your pet fur baby is avoiding or trying to escape as you try to play with or cuddle them, it may mean that they dislike your presence by the time and projecting aggression. 

  • Open mouth hissing

Just like a snake hiss, your rat can also hiss back at you, if he is not in a good mood to accept your play or cuddle offer. Hissing is a prominent sign when rats show their teeth with wide-open mouths and signal to leave them alone. This aggressive behavior could also sprout to project dominance or territorial marking

  • Fluffing up

This is also known as postering in fancy pet rats. When your pet fur baby may feel threatened due to any external influence, they will fluff up their body hairs to project size growth and dominance over the thing, other pet or family member who is possibly standing in his way. 

  • Jump attacks

Jump attacks are also commonly projected by aggressive pet rats. Whatever the reason for his or her aggression, rats being small pets, easily jump on human parents, other pets, or fellow cage mates who threaten their existence. If you find your male pet rat jumping to attack you or someone else, take it as a sign of aggressive behavior

Reasons For A Male Rat Aggression

I totally understand how heartbreaking and horrifying it is to see our pet rats become aggressive and monstrous. Projecting dominance may be feeling threatened or ill from within, this situation is unpleasant for both pet rat parents and the animal himself. 

However, even after calculated actions by most pet rat breeders, the chances of aggressive pet rats are still not fully eliminated. To clear your confusion and questions revolving around sudden aggression in male rats, there are certain facts mentioned below to help you to understand the situation of your little fur babies better.

Aggression in male rats or fancy pet rats, in general, can be caused due to:

The Environment They Grow Up In

Some experiments and medical reports have shown that environmental influences also affect behavioral patterns in fancy pet rats. Sometimes pregnant mothers when staying in a challenging, noisy, and unhealthy space, her stress can affect the DNA of the babies in her womb. This will also lead to aggression in baby rats. As these rats grow up, aggression can show up suddenly and this may come as a shock to their beloved human parents. [Source: SciELO Brazil]

Hormonal Imbalance

Hormones contribute to building up and reflecting biological, emotional, and mental signals in all animals. Fancy pet rats are no exception in this. Cortisol, for example, is the stress hormone in male pet rats. Oxytocin on the other hand determines the level of happiness in rats. Surges or fluctuations in these hormone levels in rats can also result in sudden aggression. These hormonal changes are mostly witnessed during the growth week and months of rats. 


I know it is a bit of a hard pill to swallow, but it is also a bitter truth about our little pet fur babies. Aggression can be a personality trait in your male pet rat, that he might have inherited from his parents. Yes, you may claim a gene test to understand if aggression is a product of mutation or not. But, alas again, gene tests are not possible for rats. So, in case your pet rat has undergone any mutation or carrying it in his/her genes, aggression can be hard to eliminate. 

Unidentified Diseases

Your perfectly healthy-looking pet furry friend may be suffering from a chronic disease from within. Sometimes, it happens that no matter how much healthy food your rat baby may consume, tumors and respiratory diseases or subtle blindness start growing inside their body, without any physical symptoms or changes. These diseases during the initial stages may cause irritation and sickness, making your little pet friend project aggression. 

Other Causes For Aggressive Aat Behavior:

Besides improper breeding by licensed small animal breeders and biological factors, there are several other external and man-made influences behind rat aggression. Your pet male rat may become aggressive suddenly due to the following reasons as well. 

Past traumatic human experience: This situation is mostly witnessed by pet rat parents who adopt rescued rats. Any prior human experience may be highly abusive and torturous for the little furry friend that you have recently welcomed home. Love is alien to this little rat pet and he/she has not experienced human companionship before. Thus, when you wish to play or cuddle or interact with your little rat friend, the first reaction is to bite you or show any other sign of aggression and resistance,

Maternal aggression: In the case of female pet rats, aggression can be witnessed during pregnancy or post-pregnancy. Mothers are usually very protective about their babies and dislike any unnecessary human interference during this phase of their life. If you witness any pregnant rat mother projecting aggression or hissing as you try to approach her, it is wise to stop right away. Allow her all the much-needed privacy and space she demands.

Territorial dominance: Rats may be cute and adorable and love human companionship, but their attitude towards fellow cage mates are not the same. Fancy pet rats, especially males, are very much dominant and territorial in nature. It is always better to keep two males in separate cages. Rats prefer to pee, mark, and even softly bite to project their dominance over their human parents. However, the signs of dominance and aggression may change into fights when it comes to their counterparts.

Provocation: There is absolutely no point to provoke any animal and in this case the innocent rat babies. Maybe you, as a responsible pet rat parent, try to provoke your rat playfully. But, this can have adverse effects and make your pet rat grow further signs of severe aggression like biting, scratching, and fighting with other cage mates too.

Other pets: if you have other pets in the house like a cat or a dog, their presence may be intimidating to your little rodent buddy. This can also cause fancy pet male rats to turn aggressive suddenly to project their dominance over these animals as well. 

Space shifting: Shifting the rat cage from one space in your house to another is never a good idea. This habit of frequently shifting a rat can cause them high stress and this will only result in more aggressive behaviors towards you. 

These are sometimes subtle signs more pet rat parents may fail to notice. However, it is better to research and keep your knowledge polished about your pet rat buddy. This will only help responsible pet parents to understand and identify and help them heal the sudden aggression. [Source: PMC NCBI]

How To Calm Down An Aggressive Pet Rat?

As you have already identified that your little fur babies are agitated, frustrated, and aggressive due to stress, hormonal imbalances, or any other external influence, it is time to focus on helping them get back docile. 

Bringing your fancy pet rat back to its mild and calm, loving form may require you to put in genuine long-term efforts. You can help your furry friends by getting them trained by a licensed pet rat trainer, or you may try these below-mentioned steps and tricks to help them reduce their aggression. 

Here are some common yet powerful tips to help all the pet rat parents help their rat babies heal and get back docile and calm. 

Training: Yes, you may have litter trained your pet male rats already. However, it is now time to teach them what is right manners are. This may seem funny sometimes, but rats need to be trained in manners. Some of these little rodent pets have really difficult and aggressive personalities by birth. You can try training these pets from a young age to help them get comfortable with human interaction and be calm and loving at the same time

Patience and love: Parenting a child or a beloved pet is not an easy task. Parenting comes with the need to be patient, affectionate, and understanding in order to help these animal babies grow and live healthy lives. While parenting an abused rat or rescued animal, we must be extremely patient while they relearn to interact with humans and understand that not everyone is here to cause them harm. Teaching how to trust again, love, and enjoy being played and cuddled around, will take loads of effort, love, and patience. 

Timely checkups: Rats are small pets belonging to the rodent family. There are certain diseases that flow in their genes and commonly develop in almost all of them. Tumors, respiratory infections, and blindness are to name a few. These diseases may not always show physical signs in a rat body during the initial stages. However, the same start causing irritation, stress, and aggression in our little rat pets. It is thus important to maintain regular or periodic vet visits to avoid stress and aggression due to subtle illness. 

Proper environment: Try to provide a healthy environment for all your pet rats. It is not only that pregnant rats need special attention. A healthy environment is a necessity for the healthy growth of any animal that you have adopted. If your rat has suddenly turned aggressive, have a look around the environment they are growing up in. It is wise as responsible pet rat parents to shift your rats in a comparatively calmer, well-ventilated room.

I hope this write-up has helped you to understand and identify all the possible reasons behind the sudden aggression of your pet rats. It is hard to see our little fur babies in pain and irritation. However, if we have enough information about proper training habits, we can heal our beloved rat pets.