Materials and Methods

Forty cats were studied; 20 did not have elimination behavior problems (nonproblem group), and 20 did have elimination behavior problems (problem group). Consenting owners and their cats were recruited in this study through referrals from local veterinarians, flyers on the campus bulletin boards, and newspaper advertisements.

For inclusion in the study, household cats had to be at least 1 year old and not more than 12 years old, clinically normal, and kept entirely indoors; there had to be only 1 cat in each household. Cats were considered clinically normal on the basis of results of physical examination, CBC, serum biochemical analyses, and urinalysis. For purposes of the study, cats that eliminated outside the litter box at least some of the time were defined as having elimination behavior problems.

In all households, a camcorder was positioned outside the litter box to record the sequence of behavior of each cat prior to and during elimination and the behavior exhibited afterwards. In households with a cat that had elimination behavior problems, a second (and if necessary, third) camcorder was used to record the pattern of behavior at areas outside the box in which the cat eliminated. The camcorder recorded continuously for 72 hours starting between the hours of 6:00 PM and 8:00 PM. The tapes were replaced once daily.

Durations of elimination-associated behaviors were recorded from the videotapes. These behaviors included covering (raking substrate over waste in litter box by use of the forelimb feet), digging (use of the forelimb feet to rake away substrate to form a shallow hole; may consist of a sequence of left and right or right and left foot movements), pawing (cat rubs feet over materials or objects other than the litter), and sniffing (nose held within 3 cm of object). Other factors that were also recorded included type of litter box (hooded vs not hooded), sex and age of cat, type of litter (clumping vs nonclumping; scented vs unscented), whether cat was declawed, whether cat was neutered, number of litter boxes in household, frequency of litter box cleaning, number of years the cat was owned, and the type of elimination behavior problem. The study focused on inappropriate urination on horizontal surfaces and defecation.

Four 100-minute samples were taken of each cat's use of space in the house. Every minute, the cat's location in the house was recorded on a map. One sample was recorded during each of the following time periods: 7:00 AM to 10:00 AM, 10:00 AM to 1:00 PM, 1:00 PM to 4:00 PM, and 4:00 PM to 7:00 PM. These data were used to determine the cat's home range and core area within the house.

Statistical analysis—Because the home range of each cat differed, the adaptive kernel method was used to calculate home ranges for each individual. This nonparametric method was chosen because the home ranges for each cat varied in distribution parameters. By use of the adaptive kernel method, all data points were plotted on a grid structure overlaid on the home range of each subject. The home range for each cat was calculated from a complete utilization distribution, which provided the relative frequency of the cat's locations over all observation periods.²³ Home ranges obtained through use of the adaptive kernel method also provided a density estimate. The density estimate indicated the amount of time the cat spent in each area of the home range.^24,25 The datum points were also used to determine the smallest area that accounted for 75% of the cat's area of activity; this was defined as the core area, which was the center of activity and the area of greatest utilization.²⁶ The noncore area was the peripheral area that was less commonly used but was still part of the total home range.

To assess the location hypothesis, χ² tests were used to determine whether there was a difference in litter box location between cats in the problem and nonproblem groups, whether the nonproblem group had litter boxes located disproportionately more within the core area than the noncore area, and whether the problem group had litter boxes located disproportionately more within the noncore area than the core area.

To assess the core area hypothesis, the area in which 10% of the cat's activity took place (ie, accounted to 10% of the datum points) was identified and defined as the central core area. The geographic center of the central core area was determined, and the distance from the geographic center to the litter box was measured. A Pearson correlation was used to test for the presence of an inverse correlation between the time each cat spent digging, sniffing, covering, or pawing during elimination and the distance of the litter box from the central core area.

To assess the elimination behavior hypothesis, a 1-tailed t test was used to test whether cats in the problem group would dig and cover less than cats in the nonproblem group.

Several variables were evaluated by use of a χ² test to ensure that there was no significant difference in the distribution of variables other than those of focus between the nonproblem and problem groups. The variables included sex, age, neuter status, declaw status, and duration of ownership of cat; type of litter box; type of litter; number of litter boxes; and frequency of litter box cleaning. Overall, 10 c2 tests were performed and a Bonferroni correction was used for the P value. Thus, a significant effect was defined at a value of P < 0.005.

All data analyses were performed by use of statistics programs,^a,b with a significant effect defined at a value of P < 0.05. Intraobserver reliability was calculated on the basis of 10 randomly selected samples.

Results

Complete videotape data sets were collected for most cats. Some short segments were missing because the owners turned the tape off for privacy. When this happened, data collected were adjusted to a 12-hour equivalent. Results of analyses to determine whether variables other than those of primary focus were affecting data indicated that there were no significant differences in those variables between the nonproblem and problem groups (Table 1).

Assessment of the location hypothesis—In 37 of 40 households, the litter box was located in an area of the house that was not part of the cat's core area. Litter box location was not significantly different (χ² = 73.0; P > 0.05) between nonproblem and problem groups. The nonproblem group had litter boxes located disproportionately more in the noncore area than was expected (χ² = 139.26; P < 0.05). Similarly, the problem group had litter boxes located disproportionately more in the noncore area than the core area (χ² = 52.267; P < 0.05).

Assessment of the core area hypothesis—There was an inverse correlation (P < 0.05) between sniffing and the distance of the litter box from the central core area (Figure 1); the closer the litter box was to the central core area, the more the cat sniffed (r = −0.318; P = 0.038). There was no significant correlation between distance of the litter box from the central core area and the amount of time spent digging (r = −0.146; P = 0.184), covering (r = −0.132; P = 0.208), or pawing (r = 0.067; P = 0.340) within the litter box.

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Inverse correlation of the distance of the litter box from the central core area and duration of sniffing after elimination by cats with and without elimination behavior problems (20 cats/group).

Citation: American Journal of Veterinary Research 67, 9; 10.2460/ajvr.67.9.1500

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Assessment of the elimination behavior hypothesis—Mean ± SE time spent digging was 12.4 ± 9.1 seconds for cats in the nonproblem group and 4.0 ± 3.8 seconds for cats in the problem group. Cats in the problem group spent significantly (t = 3.793; P = 0.002) less time digging in the litter box than did the control cats. Cats in the nonproblem group spent 15.7 ± 11.1 seconds covering after elimination, whereas cats in the problem group spent 9.8 ± 10.7 seconds covering. However, there was no significant (t = 1.709; P = 0.192) difference in the times that the 2 groups of cats spent covering in the litter box.

The mean number of occasions that cats eliminated per day was 5 for cats in the nonproblem group and 3 for the cats in the problem group. In the nonproblem and problem groups, mean time spent pawing after elimination in the litter box was 6.4 ± 7.8 seconds and 6.5 ± 11.3 seconds, respectively, and mean time spent sniffing after elimination in the litter box was 21.1 ± 8.9 seconds and 15.3 ± 11.7 seconds, respectively. Because there were no significant differences in duration of 3 of the behaviors (covering, pawing, and sniffing) between problem and nonproblem groups, the data from all 40 cats were pooled. Overall, mean time spent covering after elimination in the litter box was 12.8 ± 11.8 seconds, mean time spent pawing after elimination in the litter box was 6.5 ± 1.5 seconds, and mean time spent sniffing after elimination in the litter box was 18.2 ± 1.7 seconds. The intraobserver reliability, which was averaged over frequency, was 83% for sniffing, 100% for digging, 88% for covering, and 86.6% for pawing behaviors.

Discussion

Various factors may contribute to inappropriate elimination behavior problems in cats.^4–6,9 The study of this report was performed to assess whether inappropriate elimination behavior in cats may be caused by the inappropriate location of the litter box in the household. It was expected that the location of the litter box would differ between cats that always used the litter box and cats that engaged in inappropriate elimination. However, results indicated that litter box location did not differ between cats with or without elimination behavior problems. This finding may suggest that the location of the litter box did not contribute to the cause of inappropriate elimination in the cats in the problem group. In 37 of 40 households in the present study, the litter box was located in an area of the house that was not part of the cat's core area. The litter box was unknowingly placed outside the core area by the owners. Therefore, the cats in our study usually did eliminate outside their core area.

The core area, as defined in the present study, may have included too much or too little of each cat's area of activity to accurately evaluate the importance of location. More research is needed to successfully identify a core area, which would include a latrine area. Further studies will be required to determine whether cats avoided spending time near the litter box (therefore, the litter box was not in the core area) or whether owners placed the litter box in areas that were not likely to be part of the cat's core area for reasons unrelated to elimination behavior.

There may be other motivating factors that contribute to a cat's litter box usage. One factor that may have an important effect on where a cat chooses to eliminate is the location of food and water; this aspect was not a focus of our study. A cat may prefer to have a latrine area closer to where it feeds, and this may be more important than having a latrine area closer to where it spends 75% of its time.

Data obtained from observing feral cats have suggested that cats behave differently before and after elimination depending upon the area in which they were eliminating. Liberg¹⁶ and Panaman¹² reported that cats covered after elimination within the core area. When cats eliminated in areas outside the core area (noncore areas), they did not cover after elimination as frequently as they did after elimination in the core area. The results of the present study indicated that the time spent digging, covering, or pawing in the litter box was not greater when the litter box was located closer to the central core area; however, cats did engage in sniffing more frequently when the litter box was closer to the center of the core area. It has been determined that cats usually sniff places where feces are buried.¹⁹ Our data suggest that odors may be more relevant to cats in the central portion of their core area.

In 1 survey,²⁰ many owners reported that their cats with inappropriate elimination problems did not dig prior to elimination in a litter box. The results of the present study support that finding, indicating that cats with inappropriate elimination problems do not spend as much time digging prior to elimination as do cats without inappropriate elimination problems. Because cats that always used the litter box spent more time digging in the substrate, failure to use the litter box appears to be substantially affected by variables that are likely to affect digging, such as substrate preference or aversion.

No difference in the time spent covering after elimination in the litter box between the problem and non-problem groups was detected. We had expected to find a difference in this behavior between the 2 groups. One reason that a difference was not detected may be that the litter boxes in both groups in our study were frequently located in the cats' noncore areas. Previous investigations^12,16 have revealed that cats did not cover after eliminating outside the core area, but did cover when they were within the core area. Another explanation of why different results were obtained in the present study is that different definitions of core area may have been used in both previous investigations.^12,16 In those studies, the core area was not specifically defined as the smallest area that accounted for 75% of the cat's area of activity. Another factor that may have affected the results was that all the cats in our study were kept entirely indoors, whereas the cats in the previous investigations were free-ranging cats living on farms.^12,16 Therefore, 2 main factors (cats being housed indoors and owners choice of litter box location) may have affected the behaviors of the household cats included in the present study enough to produce results that differed from the results obtained for free-ranging cats.

In the study of this report, there was an even distribution of cats with intact claws and declawed cats in both the problem and nonproblem groups. There are no data from our study that support the idea that declawed cats have elimination behavior problems more frequently than cats that were not declawed.

Results of the present study have several implications for the treatment of inappropriate elimination behavior problems in cats. The finding that cats with such problems spent significantly less time digging in the litter box indicated that factors other than litter box location, such as litter aversion, substrate preference, box size, and frequency of litter box cleaning, may contribute to their preference to eliminate outside of the litter box.^4–6,9 This study has delineated the digging times of cats with and without elimination behavior problems, but future studies should be performed to assess whether a cat's actual digging times can be used as a means to test for litter preference or aversion. Veterinarians can also ask clients to obtain digging time measurements of their cats with elimination behavior problems to better assess the relevance of this problem in their particular cat's case. The owners can then be instructed to obtain a substrate that their cats prefer to dig in or make other modifications in litter and litter box management.

For the households in the present study, the location of the litter box in the core or noncore areas, as defined, was not related to the presence or absence of elimination behavior problems. This finding does not provide conclusive evidence that litter box location does not affect where a cat chooses to eliminate. The study parameters may have differed from parameters set by previous researchers in this field; therefore, different results were obtained. It is impossible to determine whether this is the case because previous researchers did not report explicit definitions of core and noncore areas. Further studies that take into account the location of food and water and the exact distance of the litter box from the cat's central core area are needed to determine whether litter box location has an effect on a cat's usage of the litter box. However, it is hoped that information obtained from our study might be used to reduce the incidence of inappropriate elimination and the likelihood that cats will be relinquished to an animal shelter or euthanized because of inappropriate elimination behavior.