Behaviour

Rat behaviour is such a huge and nuanced topic that I tend not to like commenting on it online and with generalisations. Context and background are so important, and the descriptions provided by owners may not necessarily be accurate. Nevertheless, it is a huge aspect of rat ownership, so it is worth addressing where I can with the disclaimer that not all circumstances will be addressed, and one approach to resolve behavioural issues won't necessarily suit all rats. It is also worth noting that some behavioural issues are due to a hormonal imbalance and/or pain, and in these instances veterinary care should be sought.

Below is an infographic outlining different postures taken by rats and the emotions they tend to convey. Note that the eyes may also appear to bulge more when the rat is scared.

Nipping

Below is an infographic I have made covering the most common reasons why a rat may nip. This is not to be confused with little "nib-nibs", as I like to call them, where the rat is grooming you. This is usually accompanied by licking. I personally wouldn't class nipping that doesn't break the skin as an aggressive act as it is usually exploratory or a way to try and communicate that they don't like something. Rats can't speak to us, so they have to use the means they have to communicate. It is our job to recognise this communication, figure out why it is happening, and rectify it so that the nipping behaviour (which is undesirable) stops. If nipping is ignored (except in the case of exploratory nibbles), then it will likely continue and the behaviour may escalate into aggressiveness, which no one wants. While pet rats are largely bred to be good-natured, we should not take this for granted, ignore what they are telling us, or push them beyond their limits. This sets everyone up for failure and bad experiences.

Fear-based Behaviour

There are a variety of reasons why a rat may be fearful. They may have:

A shy nature;
Lack of socialisation to people and/or new things;
Have come to a new home;
Been bullied by cage mates;
Been mishandled, either through nervous handling or mistreatment; and/or
Had some form of bad/stressful experience.

In any case, myself and rescues I am friends with have found that these rats tend to need a calm, respectful and kind approach where interaction is on their terms. I recommend taking a desensitisation approach, where you focus on building trust and confidence. I have found that rats approached in this manner become more resilient with time and they make fantastic pets. Having confident friends for them to watch also helps, as they can see that there is nothing to worry about.

If a rat is fearful due to bullying by cage mates, signs may include looking run down, consistently having bites and scratches, and staying away from the main group. You can attempt to rectify this through reintroductions and splitting the group. The aggressor may require neutering.

Confident Handling

The way that we handle our rats can have a huge influence on their behaviour. If they are the naughty sort, they may push boundaries with nervous handling. If they are the shy sort, they may become fearful. It is very easy to say "just handle the rats confidently", but another thing entirely to do it. Building confidence takes time, but what can you do to foster that in the meantime?

Fake it 'til you make it! Think about what you would like to do and go in with a sense of calm certainty. Scooping them up can help if you're worried about them moving away. Avoid snatching them quickly and making indecisive attempts at handling.
Be calm! Rats can often sense when we are frantic or in a rush, and this in turn can make them feel on edge. If you find yourself starting to get worked up, take a moment to take some slow breaths and recentre. Consider whether you need to interact with them in a simpler way, such as sitting at the cage door instead of trying to play or offering your arm instead of your hand.
Don't look at who you're handling! You may have a rat that you have become nervous of for some reason, be that because of nibbling or because they have been skittish. Consider whether you have been treating them differently since, and whether the way you handle them compared to the others (eg. being more cautious) may be feeding into their response. If you can pick up one rat confidently but not another, channel that feeling of confidence.
Take things slow! You can use a desensitisation approach to build a bond. This way you can become more confident with smaller steps such as stroking them and putting your hand around them. Plus they can grow in their confidence too as they'll have lots of little positive interactions with you and not be phased by faffing.
Practice! If you are able to, practice handling with other rats before bringing home your own. If you are obtaining your rats from a rescue or breeder, they will be able to give you pointers. It is a good idea to pick your rats up and put them into the carrier when you bring them home so that you've already handled them once before they come home and it doesn't feel like as much of a big deal.

When Might A Rat Require Neutering?

Rats, like humans and other species, can have "teenage" phases. This is when they come out of kittenhood and their hormones start kicking in. They begin to test boundaries within their group and this can lead to periods of unrest. It is easy to label this behaviour as hormonal aggression and warranting a neuter, however it is worth examining what behaviours are being seen and, if relatively mild, seeing if the behaviour becomes a sustained pattern. Most rats who have a teenage phase will test boundaries, be swatted back into their place by their group, and life goes on. Some rats keep trying for a short while, and then calm down. Some rats improve once their group dynamic is changed (reintros, splitting the group, or introducing into a different group). But some rats take things too far with behaviours such as bullying members of their group, or responding to interaction in an out-of-proportion, aggressive manner. It is worth considering neutering for this final group of rats. Neutering removes the hormones at play and can lead to a happier rat.

Rats can also become aggressive out of fear, usually in response to a negative experience. These rats require time and patience to work past their issues. Calm and assertive rats can often help by de-escalating situations/not feeding into stand-off-ish behaviour, and showing the fearful rat that there is nothing to worry about. Neutering can be effective, though is not a cure-all.

Repeated exposure to unfamiliar rats and competition are the most common scenarios posited by Albert et al (1992) that are likely to be experienced by pet homes. If you would like to have a larger group, consider where you are sourcing them from and the rats' relatedness. Related rats tend to think alike and get on better. Also consider the availability of high-value items and whether the rats are becoming territorial over them.

The two main options for neutering are surgical castration, where the testes are removed, and chemical castration using an implant (suprelorin is the most commonly used one currently). Surgical castration is often cheaper, means that the rat can live in a mixed sex group without reproducing, and is permanent. The implant is more expensive, doesn't make it safe to cohabit with the opposite sex, and wears off after time. Some rats also experience a surge in hormones after the implant. The implant is a good idea for rats who have health issues as they don't have to go under full sedation for it, but otherwise I would recommend surgical neutering for the reasons provided above.

It is worth noting that while hormones regulate behaviour, not all aggressive behaviours are purely hormonal in nature. Undesirable rat behaviour is frequently labelled as aggressive and needing a neuter online, but, as with everything relating to behaviour, the wider context matters. Rats have thoughts and feelings and can pick up on our emotions and nerves. Rats, as mentioned above, can have teenage phases. Rats will put other rats in their place if warranted. They're not going to join hands and sing kumbaya all of the time, especially if they're in a large mixed-personality and/or -age group, or if introductions are being done in a sub-optimal way. They're allowed to have emotions and have intricate group dynamics; their intelligence is one of the things that makes rats so amazing as pets.

If you are finding that all/a lot of your rats are requiring neuters or that a neuter is being recommended as a first port of call, take some time to evaluate what behaviours you're seeing by trying to use words other than “aggressive”. Some examples of other adjectives could be “defensive”, “anxious”, “confused”, or “tense”. Also consider the trigger for these behaviours. Consider whether any of your actions/goals could have been a factor and whether you could change your approach. Consider the impact of these behaviours on the group (injuries, loss of condition, everyone being on edge and/or temporary tension).

I am not anti-neuter, nor do I seek to minimise aggressive behaviour or be prescriptive in any way. But I do want to encourage owners to try to better understand their rats’ behaviour, their own behaviour and how they respond to issues, and to address the sometimes underlying causes of rat behavioural issues or general unrest in the group. Neutering shouldn't always be our first go to "quick fix" as it means we lose our appreciation for the nuance that comes with rat behaviour, and it may mean missing important behavioural triggers and not addressing the root cause.

Medical Treatment & Behavioural Euthanasia

If the rat has a sudden change in temperament with no other obvious external factors, it is worth investigating the possibility of a health issue. Note down any other potential symptoms of illness and have the rat examined by a vet. As an example, there have been cases where a rat has suddenly become aggressive to people and/or cagemates and it turned out the rat had cysts on their ovaries. The rat returned to normal after a spay.

While it is a heart-wrenching and difficult topic, behavioural euthanasia is important to be aware of when working with a rat with particularly bad behavioural issues. We euthanise animals for medical reasons, and deep-rooted behavioural issues that cannot be improved upon is as much of a medical issue as a pituitary tumour or similar. It impacts the rat's quality of life to the point where they cannot have a fulfilling life. If the rat is aggressive and destructive with no hope of improvement, it is highly likely that something is deeply wrong neurologically or the trauma they may have been through was too much. The humane path is freeing them of that suffering. Thankfully, behavioural euthanasia is very rare as other interventions such as neutering or proper introductions tend to resolve the issue. If your rat is showing minor misbehaviours such as nipping, do not worry yourself by immediately putting behavioural euthanasia on the table. It tends to be considered for rats where neutering doesn't work (even after giving ample time for hormones to settle), where highly aggressive behaviour is shown with no real reason or trigger, and the rat is visibly unhappy whenever anything minor happens (eg walking past the cage).