Those that have welcomed pet rats into their home know how much fun these little critters can be. Full of personality, they thrive in groups and love to explore their surroundings. But compared to more common pets like cats and dogs, rats pass urine on a very regular basis. For some owners this can give concerns about mess or hygiene. Sometimes it can be hard to know if it indicates a health concern, especially to those new to rat ownership. So, understanding what is normal can be a key step to monitoring the health of your rodent companions.

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Why does my rat pee everywhere?

Like many mammals, rats have a keen sense of smell and rely on odours to communicate with each other and interpret their environment. Urine is full of chemicals and pheromones that create an animal’s scent. Every time your rat urinates, it releases a unique odour that tells other animals who made it, what sex they are, and whether they are fertile or not.

Given that rats are social creatures and best kept in groups, each rat within that community will urinate regularly as part of their social communication. By passing small, regular spots of urine, rats will mark objects, their housing, and even their food to indicate ownership or to mark something as safe. This may even include you as their owner.

Rats also urinate on each other depending on their status in the group

Males are more likely to mark than females. Castrating males may decrease the behaviour; but both sexes (entire and neutered) and all age groups will mark to some degree. If you have fertile rats, this marking behaviour may vary with intensity in line with the female’s heat.

Additionally, like many foraging species, rats urinate to create odour trails as they move around their home turf and explore further afield. This allows them to retrace their steps and relocate their favourite places.

With these reasons in mind, it can be difficult to toilet train a rat. They may learn to pass faeces in a litter tray but will likely continue to pass urine elsewhere. So-called ‘pee rocks’ placed in desirable spots may be a useful training aid though.

What is a normal volume?

Pee marking differs from urination in volume and frequency. As rats have many reasons to pee mark, they don’t tend to hold urine in their bladder for long periods, meaning most of the urine that you see your rat produce will be spots, dribbles, or small patches. Rats produce between 13-23 millilitres of urine in a 24-hour period, but you are unlikely to ever be able to measure this as it is much less common to find a full bladder evacuation.

Larger volume urinations can occur however, and don’t necessarily mean your rat is sick. But it may mean they are stressed or agitated. A freshly woken rat may pass a bigger volume of urine than one that’s been awake for hours, but you are most likely to see a bigger volume passed when you take your rat to the vets, or it is handled by somebody unfamiliar, or put into a transportation box. Stressful and unfamiliar situations are a common cause of temporary abnormal urination.

When to be concerned

One of the biggest challenges of monitoring rats in a social group is being able to see who is producing what. Being familiar with each rat’s normal can be the best way to monitor their health over time. With a new rat or large group, this may not be so easy, so there are a few things to bear in mind.

Like us, the colour of your rat’s urine can change across the day. The most common colour will be a variant of yellow. Some fruits and rat treats contain dyes that can taint urine meaning you may notice a change in colour after feeding your rat certain foods. If you see a colour change with no explainable reason, especially if it appears pink or red, then a trip to the vet clinic would be best.

Volume and frequency changes may indicate a problem. Producing more or less urine than normal, going longer between urinating, or visibly struggling with passing urine, are all concerning symptoms. If you see any of these, your vet should examine both your rat and their urine to determine what is wrong.

Causes of abnormal urination

Like other animals, rats can lose organ function as they age. Diabetes is rare in rats, but chronic kidney decline can occur from 1 year old and is progressive with continued ageing. Known as chronic progressive nephropathy, or ‘old rat nephropathy’, it is more common in males than females. Rats fed a diet too high in proteins are at an elevated risk.

As the kidneys cannot adequately do their job of concentrating urine, it becomes more dilute. This may be seen as a change in urine volume, but symptoms also commonly include weight loss and reduced appetite.

Kidney function can also be compromised by bacterial infections

These infections can trigger inflammation in the kidneys, called nephritis. Pyelonephritis is an acute form of nephritis that occurs due to bacteria in the lower urinary tract (the bladder and urethra) travelling into the kidneys. The inflammation can cause discolouration of the urine, especially blood tinging, and may cause it to look gritty.

A few diseases of the bladder can make urination difficult, and this may make your rat appear to be peeing less than usual. A parasite infection known as bladder threadworms can occur without symptoms, however the threadworms can act as a physical plug limiting the passing of urine. If this occurs, your rat may appear subdued or uncomfortable, or you may see it try to urinate with little or no success.

Other causes of urinary output blockage include bladder stones which can form in abnormal urine

Although uncommon, the risk of formation is highest in older rats, and males are more prone than females. Male rats also naturally have a higher level of protein in their urine and in rare cases, this can create a protein plug that can block the bladder outflow. Cancerous growths are another rare cause of problems passing urine.

A complication of abnormal urination is the development of urine scald, a skin condition that results from the burn of alkaline urine sitting on the skin for too long. This is a particular risk with increased volume of urine or if your rat is less active or overweight. It is a good idea to get your rats used to regular handling so that you can check their underside frequently.

At the end of the day…

There are many reasons why your healthy rat will appear to urinate a lot, but if you aren’t sure, or if you notice something unusual, then your vet can assess your rat’s health, and its urine health. Urinary tract conditions could be serious for your rat so the sooner help is sought, the better chance that you and your veterinary team can manage it.

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