I have spent most of my working life watching how captive animals use the space we give them, and rats are one of the most telling species to observe. Give a rat a flat, cramped box and it paces or over-grooms. Give it height, hides, and ropes, and you see foraging, wrestling, and rest in a tight social group. That is the lens I brought to the MidWest Critter Nation single unit, and after four months with three rats living in it, I have a clear view of where it earns its reputation and where you have to intervene.
Why trust this review
I am Dr. James Obi, PhD, and a Certified Applied Animal Behaviorist (CAAB). My work focuses on behavior and welfare in companion and small captive animals, including the enrichment and housing conditions that let those behaviors happen. I do not approach a cage as furniture. I approach it as the environment that either permits or suppresses a rat’s normal behavioral repertoire.
For this review I housed a trio of young adult male rats in a single Critter Nation unit for four months, observed them daily, and recorded how they used each level, how cleaning fit into a real weekly routine, and where I had to modify the cage before it was rat-appropriate. Where I make a welfare claim, I lean on general small-pet care guidance from the ASPCA and the AVMA, both linked in the sources below.
How I tested MidWest Critter Nation Single Unit Small Animal Cage
I assembled the unit myself, timing the build and noting every step that fought back. Then I set it up the way a thoughtful rat keeper would: fleece liners over the wire shelf, a covered ramp, deep paper substrate in the pull-out pan, plus hides, ropes, and a hanging hammock attached to the top bars.
Over four months I watched the rats at three points each day, including their most active early-evening window. I tracked which levels they chose for sleeping versus foraging, whether the bar spacing held a determined climber, how quickly I could spot-clean through the doors, and how the casters behaved on both hardwood and tile. I also pulled and washed the pans weekly to judge the real cleaning workflow, not the showroom version. My judgments come from those direct observations.
Who should buy, who should skip
Buy this if you keep two or three rats and you want a cage that gets the fundamentals right without forcing you to retrofit the bar spacing or the door access. It is also the cage I point new rat owners to when they ask for one purchase that will last the animals’ whole lives.
Skip it, or look at the double unit instead, if you run a larger colony of four or more rats, because a single unit fills up fast once you add levels of enrichment. Skip it too if you physically cannot maneuver a heavy, awkward flat-pack alone and have nobody to help assemble it. And if your budget is tight and you only have one or two rats, a smaller covered wire cage will technically house them, though it will not give you the same vertical behavior you get here.
Containment and bar spacing: the half-inch that matters
Bar spacing is the single most important safety spec on a rat cage, and the Critter Nation gets it right at half an inch. Across four months not one of my three rats found a gap to push through, and these were active climbers that tested every edge in the first week. For comparison, many cages marketed for “small animals” use one-inch or larger spacing meant for rabbits or guinea pigs, and a rat will escape those.
The one caveat is age. Half-inch bars contain adults and most weaned juveniles, but very young pups can slip through. I keep any litter in a solid-walled bin cage until the pups are clearly too big to fit, which lines up with the general small-pet housing caution the ASPCA emphasizes around safe enclosures.
Space for natural behavior: vertical room rats actually use
This is where the cage justifies itself behaviorally. The tall interior of a single unit let me build genuine vertical complexity: a hammock near the ceiling, ropes spanning the middle, hides on the pan floor. My rats used all of it. They slept high, foraged low, and wrestled on the mid-level shelf. That vertical use is exactly what you want to see, because a rat that only ever occupies the floor is usually a rat without enough to do.
The 36-inch width also gives real horizontal foraging distance. I scatter-fed across the deep pan substrate, and the rats spent long stretches digging and searching rather than standing at the bars. A cramped cage tends to produce bar-chewing and pacing. I saw neither.
Shelf and ramp safety: the one thing you must fix
Here is my biggest reservation, and the reason this section scores well below the others. The included shelf and ramps are bare wire. Prolonged standing on wire flooring is associated with bumblefoot, a painful ulcerative pododermatitis, in rats. The cage ships ready to use, but I would never house a rat on those surfaces uncovered.
The fix is simple and cheap. I cover the shelf with washable fleece liners and either wrap the ramps in fleece or replace them with cut coroplast. Once covered, the problem is solved, and the rats grip the soft surface far more confidently. But it is a required modification, not an optional upgrade, and the manufacturer should really address it. The AVMA’s broader welfare guidance is a useful reminder that housing surfaces are a health factor, not a cosmetic one.
Cleaning and daily access: the double doors earn their keep
The full-width double doors are the feature I appreciated more every single day. I can reach every corner, lift out a hammock, or scoop a hiding rat without cornering or grabbing at an anxious animal, which matters enormously for keeping rats relaxed and handleable. Nervous rats stay far calmer when your hand approaches openly rather than through a narrow hatch.
The deep pull-out pans are the other workflow win. They slide out, the substrate stays contained instead of raining onto the floor, and a full weekly clean took me only a few minutes per pan. Spot-cleaning the wet corner each evening became a 30-second job. Over four months, that ease is the difference between a cage you keep clean and one you let slide.
Measurements that matter
A single unit measures roughly 36 inches wide, 24 inches deep, and 38.5 inches tall on its stand. The half-inch bar spacing is the figure I would not compromise on for rats. The pans are deep enough to hold several inches of substrate without spillage, which directly supports digging and foraging behavior.
Mobility comes from four locking casters. They roll well on hardwood and lock firmly once the unit is squared, though on slightly uneven tile I felt a wobble until the frame settled. Assembly is the honest downside in the numbers: the panels are heavy, and I spent about an hour building it with a second person. I would not call it a one-person job.
How this product has changed
The Critter Nation line has stayed remarkably consistent, which in this case is a compliment. The core design, the half-inch spacing, the double-door access, and the deep pans have remained the welfare-relevant constants that earned the cage its standing with rat keepers. MidWest has kept the proven layout rather than chasing redesigns.
The one change I would still like to see is a covered or solid shelf option from the factory, so new owners are not unknowingly housing rats on bare wire. Until that happens, plan to add fleece or coroplast yourself. With that single modification, this remains the cage I recommend first for pet rats, and four months of watching my trio thrive in it has not moved that conclusion.