Why is there such a difference in what is recommended for housing space?? There is a big difference between what pet people and breeders say is best for mice in terms of space. The recommendations are intended for all circumstances, not just those categories. Pet people often think breeders are not giving mice what they need. Breeders often think pet people are not giving mice what they need. The truth is, both sides are doing what they think is best for their animals, but are coming from very different viewpoints. There are several reasons for this disconnect in perspectives, and I think those reasons are important to understand when making decisions on how to house your mice.
General advice from pet resources
A vast majority of pet resources give a much larger habitat size as their recommendation than what a vast majority of breeders recommend. The reasoning given tends to come down to one of two things. First is emotion. What would you rather live in, a closet or a mansion? Well, despite your answer (I’m weird and a closet where someone feeds me, cleans up after me, makes sure I’m healthy and entertained, etc. sounds pretty darn good to me) a mouse has very different needs than a human. What you would like is not the same as what a mouse would like. Mice are tiny prey animals and their comfort requirements are totally different from people. What makes a person feel sad, trapped, or depressed will make a mouse feel comfortable, safe, and secure. The second is using other animals as a comparison. From dogs to hamsters, there are a lot of animals that prefer large spaces. Hamsters run for miles and miles each night, and don’t do well in small spaces. There is scientific research that shows how much better hamsters do with more space than less. Wouldn’t that mean another rodent like a mouse also would like more space? When you look at the natural behavior of their wild counterparts, hamsters and mice are really not great comparisons. Hamsters love running all over the place and have huge territories. House mice, on the other hand, stay in very small nests and come out only to find food and resources. They stay mainly in tight spaces even when they leave their nests. House mice, the species we use in the mouse fancy, run through walls, along cluttered shelves, etc. to stay mostly hidden.
You can see this natural behavior come forward when either animal manages to get out of their habitat. I’ve seen so many videos of hamsters running all over the house collecting items to bring back to their nest. They just run all over the place. When mice get out, they are almost always found not only in the same room as their habitat, but wedged into some sort of tight space as close as they can get to their home. They just don’t travel if they don’t have to. They will absolutely exercise and run around their own space, but it’s not nearly the same.
General advice from breeders
The reason most breeders use smaller spaces to breed is that mice breed better that way. It happens to be beneficial to us also, but if they didn't breed well, we wouldn't do it. The reason I mention this is because rate of reproduction is one of the things research often uses to indicate levels of stress. Mice don't breed well if they are stressed, and they don't breed well in large spaces. Even if you can't see how stressed they are, there are ways to measure it. Breeders see the difference first hand between behavior in larger spaces vs. behavior in smaller spaces. Frequently new breeders will go on forums asking why they aren’t getting the litters they were expecting, or why their moms are not taking care of their babies. One of the most common solutions I’ve seen to these problems is to move the mice to a smaller habitat. That comfort for the mice gives better results.
There are also many breeders that pour through all the scientific research they can find. The research simply does not support the use of large habitats. Other than very tiny spaces, mice show little to no benefit in increasing habitat size. With no notable benefit, and the visible detriment seen during breeding, using smaller habitats makes sense.
Breeder recommendations are generally between lab sizes and pet sizes. 50 square inches per mouse is a very common starting number, because it’s not too big for small mice and not too small for big mice. This is not to say a single buck should live in a tiny 50 sq in place, though. Bump up that space for a small number of mice (100-150 sq in per is great for 1 or 2) and bump down the space for a large number (500 sq in would be 10 mice, but you can very comfortably fit 12-15).
Does this mean pet people are wrong?
There are breeders that intentionally or by happenstance breed mice that do just as well or possibly even better in the larger spaces that pet sources recommend. If a breeder uses larger spaces, only the mice that are least stressed in that area will breed. The line will continue self-selecting for mice that breed in larger spaces and will result in a line that can thrive in these conditions. If you, as a breeder or pet owner, want to use these larger habitats it is good to ask about habitat sizes used during breeding. I don’t feel the need to breed this tolerance into my mice. As a result, I have had people who opted not to listen to my housing advice end up unhappy. My mice will show signs of stress if they are in over sized and under populated housing conditions. There have been times when the mice are either more timid or showing warnings of aggression, and a simple housing change made a world of difference to their temperament.
Basically, pet people aren’t necessarily wrong, but in most cases they aren’t doing what is best for the mice. It is all done with the best of intentions, and it is entirely possible to meet in the middle of those two philosophies. As long as there is enough clutter (which is more than most people think!!!), the mice will likely be fine. However, if mice are showing stress, think of reducing space rather than increasing space, or add some more mice to give a bigger social support structure!
Scientific research
This one talks about the importance of at least enough space for separation of potty area from sleeping area and such. This is one of the reasons why we do not recommend lab minimums.
These two absolutely show they don't need tiny spaces. I am not saying they need tiny spaces. I'm just saying bigger is NOT better. These support that bigger is not better for mice.
This one talks about the importance of enrichment. No matter what size space you have, enrichment is very much needed. They don't like open spaces and they need stuff to do.
Combining all the factors of the research I have posted, and not finding any research that actually shows bigger is better (PLEASE add to the research if you have stuff, even if it counters what I am saying! I want to learn and will change if I see a reason to!!!) I say do not go too large, and make sure you have plenty of clutter. If you want to give them extra space because you want to keep adding things, I have seen a lot of people have a separate play area that they can decorate with different forms of enrichment. It allows mice to not be in a really big enclosure, but also allows owners to see them explore and be entertaining.
With all of this to think about, I hope you are able to come up with a plan that works well for you and your mice!