Most enrichment advice asks you to buy something, install something, or change your daily routine. Vertical space asks for almost none of that. In many homes the shelving already exists and is simply full of other things.
The evidence behind it is stronger than most enrichment advice gets. This is not a preference or a nice-to-have. Veterinary guidance treats it as a baseline requirement, and controlled studies have measured what happens to cat behaviour when height appears and when it disappears again.
The Guidelines Do Not Call It Optional
The reference document here is the Feline Environmental Needs Guidelines, developed jointly by the American Association of Feline Practitioners and the International Society of Feline Medicine. It organises feline environmental welfare around five pillars.
The framing is deliberate and worth noting for its bluntness. Addressing environmental needs is described as essential, not optional, for optimum wellbeing of the cat, and the recommendations apply to all pet cats regardless of lifestyle.
Elevated space sits inside that framework as a named resource. Environmental resources include food, water, toileting areas, rest and sleep areas, and elevated areas or perches. Access to an elevated area increases the cat’s vertical space and allows it to monitor its environment.
The perch is listed alongside food and water. That is the position the guidelines take.
There is also a reason owners miss the need entirely. Cats often do not express overt signs of stress and anxiety, yet they do experience it, and it is frequently caused by their needs not being met inadvertently, because of a lack of understanding of what those needs are.
What Happened When Researchers Added a Shelf and Then Took It Away
The most useful study here did something clever. It measured behaviour before, during, and after the furniture appeared.
Researchers at the Waltham Centre for Pet Nutrition worked with 29 cats housed across four social rooms, collecting video footage for two days at baseline, four days with novel shelved furniture present, and two days after its removal. The furniture itself was unremarkable: a subdivided bookcase with backing applied to half of each side, so some cubbies faced one direction and the rest faced the other.
Two findings matter.
Aggression dropped at the tense moment of the day. Agonistic behaviours occurred significantly less following the morning feed during the test phase compared to baseline. Post-feeding is when competition peaks in a group, and that is precisely where the shelving made a difference.
Removing it made things worse than before it arrived. On removal of the shelving, agonistic behaviour increased above baseline at the afternoon pre-feed point, possibly indicating aggression from frustration or a rebound effect.
That second result is the one people skip past. Taking away vertical space did not simply return the cats to their starting condition. It left them worse off than if it had never been introduced.
The cats also used it heavily. Given the ratio of new shelving to existing shelving, a statistically significant proportion of cats were found on the new structure during the test phase. The conclusion drawn was direct: exploiting unused vertical space through the addition of stand-alone shelving should be considered a valuable resource that increases useable space and reduces agonistic interaction.
Why Height Specifically, and Not Just More Floor
A separate study on communally housed cats separated the two variables and found that elevation was doing its own work. In a test with vertical enrichment, cats showed increased length of stay in refuges at a height of 0.5m compared with those at ground level, though entry frequency was higher for the ground-level refuges.
Cats went into the ground-level boxes more often. They stayed in the elevated ones. Those are different behaviours serving different purposes, and only the second one is rest.
The underlying reason is not sentimental. Cats occupy an unusual position as both predator and prey, which makes an elevated vantage point a way of observing without being exposed. Research on domestic cats in home environments found they spend significant time on elevated surfaces, particularly when stressed or in multi-pet households, with the conclusion that vertical space functions as a coping mechanism allowing retreat and a regained sense of control.
For multi-cat homes, height also does something floor space cannot. It creates separation without requiring more square metres. Two cats on different levels of the same room are not competing for the same territory.
What This Means in an Ordinary House
The Waltham study used a bookcase. That is the practical takeaway most people miss while shopping for cat furniture.
- Clear a shelf you already own. A bookshelf with one row emptied is functionally the same intervention that produced those results
- Add grip. A non-slip mat or folded towel turns a slippery surface into a usable resting spot
- Stop fighting the wardrobe top. The high surfaces cats already gravitate towards are vertical territory you have been discouraging
- Vary the heights. Low perches suit older or arthritic cats, while confident cats will take the highest option available
- Give each cat its own. In a multi-cat home, one perch creates a contested resource rather than solving one
One design detail from the guidelines is worth carrying over to the home. For multiple cats, safe spaces with more than one entryway matter, so that one cat cannot trap another. A perch with a single approach route can become a place a cat advice gets cornered rather than a place it feels safe.
Where the Evidence Is Thinner
Honesty about the limits matters here, because a lot of cat enrichment advice is repeated far more confidently than the research supports.
A systematic review of indoor cat welfare found real problems across the field. Across studies there was little evidence of rigour or systematically controlled approaches, and the common methods, cat stress scores and ethograms, were not consistently standardised, which substantially reduced the ability to compare findings between studies.
The same review flagged a translation problem. Measures were often assessed using single parameters in controlled environments, which is applicable to shelters, catteries and laboratories, but does not necessarily translate to dynamic and variable household environments.
So the Waltham cats were laboratory-housed, not pets in a living room. That is a genuine caveat.
What survives the scrutiny is that vertical space is among the better-supported interventions available. The review’s major findings included the benefits of enrichment such as hiding boxes and vertical resting spaces, as often recommended by veterinarians and feline charities, while noting that other commonly given advice, such as feeding enrichment for psychological welfare, appears scientifically untested even if not disputed.
Vertical space made the list of things that held up. Several popular recommendations did not.
The Practical Position
If you have one cat and no perch, clear a shelf this week and watch where the cat goes. If you have two or more, count the elevated spots and make sure the number is at least equal to the number of cats.
The intervention costs nothing in most homes, sits inside veterinary guidelines as a named requirement rather than a suggestion, and has controlled data showing behavioural improvement when it appears.
And there is one instruction the removal phasne of that study makes clear. Once you have given a cat height, leave it there.