Clumping vs. nonclumping. nonscented vs. scented. Activated carbon vs. sodium bicarbonate. With so many choices, it may be difficult for cat owners to know what to use. This behaviourist highlights recent research on cats' litter and litter box preferences, so you can give clients evidence-based recommendations.

While cats are the most popular pet in the United States, their most common behavioural problem for which owners seek assistance, house soiling, is unpopular with their owners. In fact, house soiling can lead to a cat's outdoor banishment, relinquishment, or euthanasia.

Studies support this regrettable outcome, with behavioural problems - primarily house soiling - being a leading cause of cats' relinquishment to shelters. In one study, more than 23% of cats relinquished to a shelter had daily or weekly house soiling incidents. A recent study found that the most common problem identified after the adoption of a cat from a shelter was house soiling, with 9% of the cats in the study exhibiting this behaviour within three months of adoption. The study also identified house soiling as a risk factor for returning the adopted cat to the shelter.

There are three main causes of house soiling in cats: underlying medical problems (e.g. feline lower urinary tract disease [FLUTD]), urine marking (communication), and toileting issues (e.g. litter box aversions, preferences for other sites or substrates). These diagnoses are not mutually exclusive; for example, a cat with FLUTD may develop a litter box aversion. Evaluating a thorough history and the results of a physical examination and diagnostic tests can direct the diagnosis and subsequent treatment.

In addition, toileting problems can stem from a variety of causes. Many toileting issues are secondary to issues with the litter or litter box. But a toileting problem can also stem from factors that are unrelated to the litter or litter box, such as intercat aggression. For example, a cat that is frightened of other cats in the home may feel vulnerable accessing or using the litter box and may ultimately select an inappropriate toileting site. So again, it is always critical to get a comprehensive history to correctly identify the motivation for the problematic behaviour.

This article focuses on new research related to litter and litter boxes that may be helpful in preventing and treating toileting problems. By getting the latest scoop on litter, you will be better prepared to prevent and resolve litter- and litter-box-related toileting problems in your feline patients.

Historical Considerations

Litter preferences probably originated with the domestic cat's evolutionary predecessor, Felis silvestris lybica, the African wildcat. A desert-dwelling creature, the African wildcat used the desert sand as its toilet, establishing a substrate preference that has apparently persisted throughout the domestication process.

With the transition of cats into our homes and the need to provide an adequate indoor toileting option, commercial litters were developed. As different options appeared on the market, preference tests for various litter types were conducted on cats. A study in the early 1990's identified cats' strong preference for finely granular sandlike material, widely known as clumping or scoopable litter, compared with large-granule litter, such as litter made of plain clay or recycled paper products. As new litters have entered the market, such as silica (crystal) litters, a preference for clumping litter has continued to prevail in comparative studies.

Litter Today

The litter market offers a wide variety of litters, including litters made of wheat, corn, paper, silica, and plain or clumping clay. Within each of these litter categories are several brands or varieties with different additives.

For example, the basic component of clumping clay litter is sodium bentonite, clay made from volcanic ash. Multiple ingredients may be added to the sodium bentonite base, including fragrances, fillers, bacterial growth inhibitors, and absorption additives, to create a unique litter product. In general, the best litter products have a substrate that cats like the feel of, provide superior odour control, and have minimal dust.

Litter Fragrance

The impact of fragrance on cats' litter preference is unclear. In one study, scented litter was a risk factor for elimination problems, but in another study, scented litter was not associated with elimination problems. Nevertheless, if cats with house soiling problems are being offered scented litter, advise owners to try offering non-scented litter.

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 behaviours [e.g. sniffing]) cedar and fish odours and showed avoidance behaviours to citrus and floral scents.

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. 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.

Odour Control

Cats may consider a heavily soiled box aversive, perhaps because of the strong malodour associated with excrement. While daily scooping and discarding of solid waste are strongly advised, additional techniques to control urine and faecal odour are desirable.

Activated carbon has been incorporated into some litters in an attempt to reduce faecal odour. While people can readily appreciate the effectiveness of activated carbon in odour 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, suggesting that it may help in preventing and treating litter box problems.

Box Size

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.  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.

Overall Recommendations

It is in everyone's best interest to identify a litter and litter box environment pleasing to cats. Research and product development will continue to advance and identify superior litter products, but it is important for practitioners to provide evidence-based advice to cat owners regarding litter and litter boxes so toileting problems are minimized.

When providing that advice, remember that cats prefer clumping litters and litters with activated carbon. If a fragranced litter is going to be used, data suggest cats prefer a cedar scent to other scents. I caution owners against purchasing citrus-scented litters, which are becoming more prevalent in the marketplace. Finally, based on the trends noted in the box size study, I recommend that practitioners advise owners to purchase large or jumbo-sized litter boxes for their cats or even consider purchasing large plastic storage boxes to use as litter boxes.

Of course, it is important to remember that you may encounter cats with unique preferences. The best way to identify an individual cat's set of toileting preferences is to offer a variety of litter choices and box styles and retain the litter and litter boxes that the cat preferentially uses. It is also wise to remind clients that no odour-controlling litter ingredients can substitute for daily litter box scooping and regular box washing.

Source: By Jacqueline C. Neilson, DVM, DACVB Mar 1, 2009 VETERINARY MEDICINE