Clay, silica, or wood pellets: what a field study reveals about cats' real litter preferences
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
Choosing a litter often comes down to comparing marketing claims: odour control, absorption, biodegradability. A study published in 2018 by Villeneuve-Beugnet and Beugnet in the Journal of Veterinary Behavior approached the question differently, by directly observing which substrate cats choose when nothing else differs (see the study). Our other care guidance is gathered in the cat care and grooming section.
Contents · 6 sections
The protocol: three identical boxes, one variable
In a first phase, 18 cats had access for four weeks to three strictly identical, uncovered litter boxes placed side by side: one with clay granules, one with silica microgranules, and one with wood pellets. No other variable changed — same box size, same relative placement, same cleaning frequency. In a second phase, 12 cats were followed for two further weeks to compare clay and silica specifically, this time using the same granule texture for both materials.
Wood clearly ruled out, clay and silica tied overall
Across all uses combined (urination and defecation together), cats showed a significant preference for clay and for silica over wood pellets, with no significant difference between the first two. A litter marketed for its light weight or plant-based origin is therefore not automatically the one the cat itself prefers: comfort underfoot appears to matter more than the raw material.
The finer finding: a preference that depends on the act
The second phase adds a nuance the overall averages had hidden: for defecating specifically, cats showed a significant inclination toward clay over silica, whereas that was not the case for urinating. A cat may therefore accept silica for one act and avoid it for the other, which explains certain partial-avoidance behaviours — a cat that urinates in the box but does its solid business elsewhere, for instance.
What this means in practice
Two practical implications follow. First, a cat that avoids its silica box is not necessarily being difficult: the grain may simply suit one particular act less well. Second, in multi-cat households, offering two different textures in two separate boxes, rather than one type everywhere, lets each cat express its own preference without it being overridden by another's — a principle that adds to our guidance on how many litter boxes to provide and where. The type of box matters just as much as the material inside it: our article on covered versus open litter boxes covers a different preference study, this time about the container rather than the contents.
The study's limits
Sample sizes remain modest (18 then 12 cats), and the study tests neither scented clumping litters nor the increasingly common material blends on the market. It measures a behavioural preference, not an effect on urinary health or on odour control as perceived by the owner.
Frequently asked questions
Should plant-based litters be avoided altogether?
No: the study compares only three specific materials and measures a usage preference, not harm. A plant-based litter that a given cat readily accepts remains a legitimate choice.
What if my cat urinates in the box but does its business elsewhere?
This study suggests that switching substrate, toward clay in particular, may be enough to resolve this kind of partial avoidance before looking into other causes. Find all our guides on the cat hub.
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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.
