What puts a cat off the litter box: not the smell, what is in the way
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
We clean a litter box mostly with smell in mind: deodorisers, scented litters, covered boxes. One study separated the two variables — what smells and what gets in the way — and the result shifts the priority. Our maintenance guidance is gathered in the cat care and grooming section.
Contents · 4 sections
Odour on one side, deposit on the other
Ellis, McGowan and Martin published in 2017, in Behavioural Processes, a study on the appeal of a previously used litter box in multi-cat households (see the study). The protocol offered cats boxes manipulated in several ways: clean litter, genuinely soiled litter, litter carrying the odour of urine or faeces with nothing visible in it, and litter containing odourless fake deposits — urine simulated with a saline solution, faeces simulated with unflavoured gelatin.
Three findings stand out. Cats do prefer clean litter to soiled litter. But the presence of urine and/or faecal odour had no effect on their choice, and the identity of the cat who had used the box before had none either. It was the odourless fake deposits that shifted preference — with a nuance: faux faeces were somewhat preferred over faux urine, so this is not a blanket rejection of anything left behind.
What the study does not say
The authors read their result as a "physical or visual" appraisal of the box. That is an interpretation, not a tested variable: no lighting or vision manipulation was carried out, and the tactile hypothesis — the cat hits the obstacle while digging — remains open. Nor does the study cover real households; it uses a reconstructed setup. And it says nothing about house-soiling of medical or anxiety-related origin. Worth knowing, finally: the three authors worked for a pet food and litter manufacturer, which does not invalidate the protocol but should be stated.
Three practical consequences
- Remove the deposits rather than mask the smell: that is the action this study supports. Our article on scented cat litter already argued the same way, but for a different reason — fragrance bothers the cat; here, it simply fails to attract him.
- No need to replace the entire litter daily if scooping is done properly: what counts is the deposit being there, not the box's residual odour.
- More boxes still helps, for a mechanical rather than an olfactory reason: more clean surface available at any moment. See our guide to how many litter boxes and where to put them.
Frequently asked questions
Is one box per cat still needed if other cats' odour has no effect?
Yes, but not for the reason usually given. The study rules out the idea that a cat refuses "the other cat's" box; it does not undermine the value of always having clean surface available, nor the management of access conflicts.
Are odour-neutralising litters useless?
For the cat, the study finds no effect. For the human living in the room, that is a different and perfectly legitimate question.
My cat urinates next to the box — does this apply?
No. Elimination outside the box has many causes, medical ones first, and this study tested only healthy cats in a free choice. A consultation remains the first step. Find all our guides on the cat hub.
In our shop, for this use: Litter scoop with stand and bag roll in the handle (€20.90) · the whole shop
For the gear, at Le Félin (same family, zero commission): Arbre à chat avec litière (from €201.99)
This guide is part of Planète Pets’s Cats universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.
