The Dancing Mouse: A Study in Animal Behavior

by Robert Mearns Yerkes

TABLE 4

AVERAGE NUMBER OF WHIRLS TO THE RIGHT AND TO THE LEFT FOR THE SIX INTERVALS OF TABLES 2 AND 3, WITH A CHARACTERIZATION OF THE ANIMALS AS RIGHT WHIRLERS, LEFT WHIRLERS, OR MIXED WHIRLERS.

AVERAGE NO. AVERAGE NO. MALES AGE OF WHIRLS OF WHIRLS CHARACTERIZATION

2 12 mo. 136.7 3.3 Right whirler
30 2 mo. 109.7 2.5 Right whirler
34 2 mo. 4.3 96.5 Left whirler
36 2 mo. 197.5 23.5 Right whirler
152 6 mo. 6.8 137.0 Left whirler
156 1 mo. 73.2 12.8 Right whirler
210 3 mo. 78.7 62.0 Mixed whirler
220 4 mo. 74.3 40.2 Mixed whirler
410 3 mo. 10.3 139.0 Left whirler
420 3 mo. 12.2 241.3 Left whirler

Average 70.4 75.8 4 Right whirlers 4 Left whirlers 2 Mixed whirlers

FEMALES

29 2 mo. 23.7 53.2 Left whirler 33 2 mo. 362.7 2.7 Right whirler 35 2 mo. 208.5 19.2 Left whirler 151 6 mo. 5.0 140.0 Right whirler 157 1 mo. 47.0 51.2 Left whirler 211 3 mo. 109.7 61.5 Right whirler 215 3 mo. 57.8 234.5 Mixed whirler 225 4 mo. 103.2 56.3 Mixed whirler 415 3 mo. 216.7 3.5 Left whirler 425 3 mo. 17.0 225.2 Left whirler

Average 115.1 84.7 3 Right whirlers 4 Left whirlers 3 Mixed whirlers

The tendency of the dancer's activity to increase in amount toward evening, which the results of Tables 2, 3, and 4 exhibit, demands further consideration. Haacke (7 p. 337) and Kishi (21 p. 458) agree that the dancing is most vigorous in the evening; but Alexander and Kreidl (i p. 544) assert, on the contrary, that the whirling of the individuals which they observed bore no definite relation to the time of day and apparently was not influenced in intensity thereby. Since the results of my own observations contradict many of the statements made by the latter authors, I suspect that they may not have watched their animals long enough to discover the truth. The systematic records which I have kept indicate that the mice remain quietly in their nests during the greater part of the day, unless they are disturbed or come out to obtain food. Toward dusk they emerge and dance with varying intensity for several hours. I have seldom discovered one of them outside the nest between midnight and daylight. The period of greatest activity is between 5 and 10 o'clock P.M.

Zoth states that he has observed the adult dancer whirl 79 times without an instant's interruption, and I have counted as many as 110 whirls. It seems rather absurd to say that an animal which can do this is weak. Evidently the dancer is exceptionally strong in certain respects, although it may be weak in others. Such general statements as are usually made fail to do justice to the facts.

The supposition that light determines the periodicity of dancing is not borne out by my observations, for I have found that the animals continue to dance most vigorously toward evening, even when they are kept in a room which is constantly illuminated. In all probability the periodicity of activity is an expression of the habits of the mouse race rather than of the immediate influence of any environmental condition. At some time in the history of the dancer light probably did have an influence upon the period of activity; but at present, as a result of the persistence of a well-established racial tendency, the periodicity of dancing depends to a greater extent upon internal than upon external conditions. During its hours of quiescence it is possible to arouse the dancer and cause it to whirl more or less vigorously by stimulating it strongly with intense light, a weak electric current, or by placing two individuals which are strangers to one another in the same cage; but the dancing thus induced is seldom as rapid, varied, or as long-continued as that which is characteristic of the evening hours.

One of the most interesting results of this study of the direction of turning, from the observer's point of view, is the demonstration of the fact that the truth concerning even so simple a matter as this can be discovered only by long and careful observation. The casual observer of the dancer gets an impression that it turns to the left more often than to the right; he verifies his observation a few times and then asserts with confidence that such is the truth about turning. That such a method of getting knowledge of the behavior of the animal is worse than valueless is clear in the light of the results of the systematic observations which have just been reported. But, however important the progress which we may have made by means of systematic observation of the phenomenon of turning, it must not for one moment be supposed that the whole truth has been discovered. Continued observation will undoubtedly reveal other important facts concerning circling, whirling, and the periodicity of dancing, not to mention the inheritance of peculiarities of dancing and the significance of the various forms of activity.