The impact of fragrance on cats' litter preference is unclear. In one study, scented litter was a risk factor for elimination
problems,8 but in another study, scented litter was not associated with elimination problems.9 Nevertheless, if cats with housesoiling problems are being offered scented litter, advise owners to try offering nonscented
Both the aroma and intensity of a fragrance may be a factor in a cat's response to it. Little published information on scent
preferences in cats is available, but a 2007 pilot study with seven cats showed that cats preferred (by exhibiting increased
engagement behaviors [e.g. sniffing]) cedar and fish odors and showed avoidance behaviors to citrus and floral scents.10
A follow-up study with 18 cats and a modified scent palate that included bleach, cedar, citrus, fish, and floral scents showed
that cats preferred bleach and fish scents to the other offered scents.11 These fragrances were not presented in the context of litter or elimination, and in that context, the results may be different.
I hope that future research will elucidate a litter fragrance that is pleasing to both owners and cats.
Cats may consider a heavily soiled box aversive, perhaps because of the strong malodor associated with excrement. While daily
scooping and discarding of solid waste are strongly advised, additional techniques to control urine and fecal odor are desirable.
Activated carbon has been incorporated into some litters in an attempt to reduce fecal odor. While people can readily appreciate
the effectiveness of activated carbon in odor reduction, a study was conducted to see if cats preferred litter with activated
carbon to litter without activated carbon. The results showed that cats preferentially used the litter with the activated
carbon,12 suggesting that it may help in preventing and treating litter box problems.
Another study was performed comparing two litter odor-control additives, activated carbon and sodium bicarbonate.13 These odor-control additives are used in two top-selling national litter brands. About 32 cats (the number of cats varied
because of adoptions) housed in four colony rooms at a shelter were given access in each room to two litter boxes and two
base litters that were identical except for the odor-control additives (Figure 1). Excrement was collected from the boxes each morning after four consecutive 12-hour overnight test periods. The amount of
excrement was analyzed by using both parametric (analysis of variance [ANOVA]) and nonparametric (Friedman) tests, using a
randomized block design. The cats showed significant (P < 0.05) increased usage of the litter box with the activated carbon additive, suggesting that the cats preferred activated
carbon to sodium bicarbonate as an odor-control additive.
Figure 1. Litter boxes prepared for the odor-control study comparing activated carbon vs. sodium bicarbonate additives. The
litter boxes were identical except for the litter odor-control additives. The litter boxes were rotated every 12 hours to
remove location preference.
A similarly designed study involving about 32 cats housed in four rooms and using two commercially available products, Fresh
Step Scoopable (The Clorox Company) with activated carbon and Arm & Hammer Super Scoop (Church & Dwight) with sodium bicarbonate,
was conducted (Figure 2). Unlike the previous study in which the base litter was identical, these two commercial products not only had different
odor-controlling agents but also had different fragrances and fillers. More excrement was deposited in the litter box containing
Fresh Step Scoopable litter, and the difference was statistically significant (P = 0.031), suggesting that the cats preferred this litter product (Neilson J, Portland, Ore: Unpublished data, 2008).
Figure 2. Litter boxes prepared for the Fresh Step Scoopable vs. Arm & Hammer Super Scoop study (one pair of boxes was not
included in the study). The boxes were identical except for litter.
It has been hypothesized that one cause of feline toileting problems is litter box aversion due to small box size. Some experts
recommend that litter boxes should be 1 ½ times the cat's body length; however, to my knowledge, no evidence supports this
claim aside from anecdotal reports and common sense. Consequently, I conducted a study to identify if cats had a preference
for a certain box size when all other variables were equal.14 To determine litter box size preference, 32 cats housed in four colony rooms in a shelter were given access in each room
to three commercially purchased plastic litter boxes equal in every parameter except size (Figure 3). The boxes were small (14-x-10-x-3.5-in), medium (18-x-15-x-5-in), and large (22-x-16-x-6.5-in) in size. The same commercial
clumping clay litter was used in all boxes. The study was conducted over 21 hours. Excrement deposited in the boxes was collected
every two hours during the daytime and in the morning, and the excrement was then counted, weighed, and recorded. Again, the
data for each room were analyzed by using parametric (ANOVA) and nonparametric (Friedman) tests. Although statistical significance
was not achieved, the trend was that the cats preferred the large boxes to the medium and small boxes based on the number
of deposits and total weight of excrement.
Figure 3. Small, medium, and large litter boxes in the colony room for the litter box size preference study. The litter was
identical in all boxes, and the boxes were rotated throughout the course of the study to remove location preference.