Response of Mice to Domestic Cat Urine

J. Graef

 

 

Abstract. Individual adult mice (Mus musculus) were exposed in an arena to the odors of cat urine and plain litter, which were placed in a cup in the corners of the arena. Both male and female mice were tested against male and female cat urine. We predicted that the adult mice would prefer the corner where the plain litter was versus the corner where the cat urine was placed. Adult mice showed no preference to where the urine was located or seemed to have no preference at all to either one of the scents. Most of the adult mice actually chose to dump the cups with the scents in them and actually performed digging and grooming behaviors.

 

Keywords: cat urine, location of scent, Mus musculus, scent preferences.

 

Introduction

Chemical cues called pheromones are used by members of several animal species to communicate among themselves (Mucignat-Caretta & Caretta 1999). In mammals, olfaction is now considered as one of the most important means of communication (Brown 1985). In rodents, it is well known that chemical signals play a role in social interactions, territorial exclusion, and mate selection. An animal can also use odors to distinguish between members of its own species and a related species as well as a predator (Christophe & Baudoin, 1998). In this study, I had examined the role of scent recognition and if an adult mouse would prefer to avoid the scent of a predator by avoiding the location the scent was in. The predatorís scent was that of cat urine.

Methods

Subjects

Eight mice (Mus musculus) were randomly chosen. Exact age of the mice was unknown at the time testing was performed however approximated age was considered that these mice were adults due to observance of body size. Each mouse was housed separately in a small cage containing wood shaving, a paper towel, a cardboard tube and a metal lid with a water bottle and pellet food.

Equipment

The arena into which mice were introduced and observed consisted of cardboard with the dimensions of: 65 cm (length) x 60 cm (width) x 25 cm (deep). The bottom of the arena was covered with 3 plastic sheets cut to the size of the arena. Each corner was labeled 1, 2, 3, and 4 according to the diagram below. Theses numbers were corresponding to where the samples were placed during the experiment, since they were rotated clockwise throughout the experiment starting at corner number 1. Samples were rotated since I randomly picked mice and I didnít want them to habituate to where the scent location was.



Samples

Fresh urine samples were collected from 3 adult cats that shared 2 litter boxes containing clumping litter. Two of the cats were males who were neutered and the other was a female who was spayed. Because I didnít know which cat had just urinated in which box, I would collect the urine samples from the 2 boxes and combined them in a bag. Samples were collected two weeks before testing so I had enough samples. Samples, once collected were maintained in a freezer until ready to be used. Plain clumping litter was collected from a fresh bag of Catís Pride Scoopable Litter bought 1 week before testing began and was stored in a plastic ziploc bag at room temperature. When testing began, samples were placed in 3 oz. Dixie cups cut to be 10 cm high. As stated above cups containing the samples were rotated clockwise during experiment. I had decided to put the samples in opposite corners starting with number 1. So for the first mouse, plain litter was in corner # 1 and urine sample was in corner # 3. As the experiment proceeded, samples were rotated clockwise so the next mouse had the plain litter sample in corner # 2 and the urine sample in corner # 4. This type of clockwise rotation continued throughout the experiment. Each type of sample was weighed out, so that amount of sample was constant for each mouse tested. Weights were not exact but most were between 13.0 to 13.25 grams. As stated above, clumped urine was combined into one bag and was a bit harder to weigh since litter was in wet clumps due to the urine. Plain litter was easier to weigh since it had a consistency of sand and was easy to scoop out.

Procedure

The experiment itself was done on Sunday, March 18th, 2000 between the hours of 11 am and 3 p.m. with all testing done inside the arena. Eight mice were randomly picked one at a time and then placed inside the arena while behavior was observed for a time frame of 15 minutes. This gave the mice time to acclimate themselves to the arena. And hopefully was enough time for behaviors to be seen. Behaviors that we had been documenting had to do with which corner the samples were placed in and as to how often each sample was approached by the mice. A chart was made and a tick mark was placed in either a column of: clumped urine, litter or other (which had to do to the two corners without a sample in it). If a mouse approached a sample and then walked forward and then moved backed up back to the sample, it was considered a preferred choice and was marked in the particular sample column. For example, if the mouse was at the urine sample and took a few steps forward and then backed up back to the cup containing the urine sample, a tick mark was placed in the urine sample column. If a mouse was not at the cup samples, and was in a corner that didnít contain a sample, a tick mark was placed in the other column. Throughout the experiment, as stated earlier, samples were rotated clockwise. After the 15 minutes of observance, each plastic sheet was cleaned due to urination and defecation issues as well as randomly picking mice led to having males and females being in the arena and I had not wanted scents of different sex to come into play as well. Samples had to be replaced often throughout the experiment. This was due to the mice that were dumping the samples over and were digging in the samples. Other mice had tried to sit inside the cups and upon getting out, dumped them. All testing performed and all behaviors observed were performed by one person.

Results

Even though specific behaviors were documented, all types of behaviors were observed during the experiment. Many mice performed regular mouse behavior such as grooming, digging and running around the arena. Some even played and chewed on the paper cups that contained the samples. As stated above, mice found the cups to be quite enjoyable in terms of play behavior by climbing in them, tipping over and falling out. The following shows the observances of the sample preference results as well as a graph showing our error bars. The results also show the mean, standard deviation, standard error and t-test results. Our P-value of 0.125 showed that the mice had no preference to the scents of either one of the samples.

Table 1. Tick marks of observed Behavior

mouse number

urine scent

plain litter scent

other

mm 6 (dk. brown, Fe)

3

2

9

mm 1 (brown, M)

10

15

25

mm 7 (brown, Fe)

9

20

29

mm 8 ((gray, M)

8

4

9

mm 9 (black, M)

10

11

24

mm 2 (blk/white, Fe)

8

13

19

mm 10 (blk/white, M)

17

19

35

mm 4 (blk/white, Fe)

13

11

23

mean

9.75

11.875

std dev

1.50260191

std. Error

0.53125

t-test

0.125091615

Since the other column included preferences that I was not looking for, it was not included in the above graph. As you can see from the data above, no matter what the sample was, mice had no preference to the corner in which samples were presented. This can be statistically seen by looking at our P-value, which was 0.125.

Discussion

The results refute the stated hypothesis and provide support that mice have no preference to location of a sample. These similarities can be seen in the data presented as well as in the graph above. Statically we can see that the P-value is 0.125, which shows that there is no significant difference to where the sample was placed. There are several possible reasons for this refuted hypothesis.

One reason possibly had to do with the behavior of male mice. The behavior of male mice is influenced by chemical cues contained in urine from other males, which are usually avoided. Adult males spend less time investigating the urine of intact males than that of castrated males (Mucignant-Caretta & Caretta 1999). Since our samples of urine contained urine from two castrated males and a castrated female, the males in this experiment didnít have a preference to the scent. They seemed to spend more time investigating both samples. This type of behavior was seen by the mice dumping the samples and digging in them or trying to sit in them. They were not affected at all by the scent.

This leads me to another reason why the hypothesis was refuted. It has been found that in laboratory mice (Mus musculus), at least four volatiles in adult male urine have been associated with social dominance: 2-sec-butly-4, 5-dihydrothiazole (thiazole), 3,4-dehydro-exo-brevicomin (brevicomin) and alpha and beta faresenes (Humphries et al. 1999). Since most of the mice urinated or defecated near the samples, I am assuming that they did not smell the volatiles that were contained in the samples used so they seemed to show their social dominance by marking the territory as theirs. Iím not quite sure if this is a reasonable possibility but it seems to be a possibility open to more discussion and research since mice use scent as a form of marking territory according to Christophe & Baudoin (1998).

Another last possible reason that I assume could have refuted this hypothesis is due to where the mice used in this experiment came from. Since these mice were from a pet store, Iím assuming that they never had contact with the outside world. How would they know that a catís urine should be avoided and if smelled is a clue that a predator is around? These mice have probably never been exposed to such a scent before and possibly havenít had the experiences that outdoor mice would have. Mice that are born and raised in the outdoors would have had experiences that would have shown them what predator scents are to be avoided.

 

 

 

 

 

 

 

 

 

 

 

 

References

Brown, R.E. 1985). The rodents II: suborder Myomorpha. In: Social Odours in Mammals. Vol. 1 (Ed. by R.E. Brown & D.W. MacDonald), pp.345-457. Oxford: Clarendon Press.

Christophe, N. & Baudoin, C. (1998). Olfactory preferences in two strains of wild mice, Mus musculus and Mus musculus domesticus, and their hybrids. Animal Behaviour, 56 (2) pp.365-369.

Humphries, R.E., Robertson, H.L., Beynont, R.J., Hurst, J.L. (1999). Unravelling the chemical basis of competitive scent marking in house mice. Animal Behaviour, 58 (6) pp.1177-1190.

Mucignat-Caretta, C. & Caretta, A. (1999). Urinary chemical cues affect light avoidance behavior in male laboratory mice, Mus musculus. Animal Behaviour, 57 (4) pp.765-769.