Do Rats Have Bladders? What About Gallbladders?

It’s a common myth that rats don’t have bladders, albeit a strange one.

In fact, rats absolutely do have bladders and they’re much the same as ours. They have good bladder control and process urine in their bodies like we do, via their kidneys.

However strange the myth may be, it may have some background in truth.

Why people may question if rats have bladders comes down to the myth that they don’t, possibly spread because of the fact that rats don’t have gallbladders, or because they often dribble their urine.

Why Do Rats Dribble Urine? Do Rats Have Bladder Control?

Rats do dribble urine, but they do so purposefully and in specific situations and locations. They use urine as a scent marker, marking their territory, specific items they like or want, and they even mark each other (or their people!) to help to identify them.

Rats have good bladder control, and are particular about when and where they urinate. While some rats are more prone to “dribbling” than others, a healthy rat will use urine as an important marker for many different reasons, even those who are litter trained.

Rats dribble urine because they’re scent marking. This marking is used for lots of reasons, including: 

• Marking other rats they want as potential mates
• Marking territory
• Marking particular objects or areas as their own
• General scenting to bring together their environment or cage mates as a group

Both male and female rats will scent mark each other. This is usually done to identify each other as cage mates, or in the case of males and females, to mark potential sexual mates.

Rats learn an incredible amount of information from this urine marking, and while potential mate marking is usually done most frequently when rats are in heat (for females, this is every 4-5 days), other urine marking is done to convey this information to each other.

Rats can learn the age of another cage mate through this urine marking, hormonal information, reproductive information, social status and probably more that we haven’t even discovered yet. They also like to mark items or cage furniture for this reason too, although there is some debate on whether urine marking is territorial.

Rat owners may wonder why their rat pees on them when they handle their furry friend. Their rats are just marking their big, human cage mate as one of their own and part of their group, much the same way as they would their rat companions. It’s an honour! 

There generally isn’t much difference between male and female rats when it comes to how much they mark. However, a female rat will use urine to mark considerably more often than her male counterparts when she’s in estrus, or heat. 

Male rats will mark in increasing amounts until they reach sexual maturity, however this can be greatly reduced if they’re neutered.

Rats can also suffer from diseases of their bladders, a common problem being uroliths, or bladder stones, which can cause bloody urine and discomfort.

Do Rats Have Gallbladders?

Rats don’t have gallbladders, and this is likely where the rumour about their bladders started. Although interestingly, their smaller mouse cousins do have a gallbladder.

The gallbladder in the human body stores bile, a substance made by the liver that is then concentrated in the bile ducts and stored in the gallbladder. For humans, this means bile is at hand ready to be used for digestion in larger quantities when a big meal is eaten.

For rats, because they eat regularly and in smaller amounts, their livers can produce enough concentrated bile at the required amount on demand to get rid of the need for a gallbladder entirely.