[The locomotor activity of the squirrel (Sciurus vulgaris)]

The locomotor activity of Sciurus vulgaris has been observed in the field and in caged animals.Onset and cessation of activity (data from the cage only): Activity starts before sunrise and correlation with sunrise is very high (0.838≤r≤0.990). Cessation of activity normally lies before sunset, during summer late in the afternoon, in winter often already before noon. It is scatterd to a greater extent than onset of activity, correlation with sunset being 0.535≤r ≤0.798.Daily pattern: It is a bigeminus, although widely subject to seasonal variations. The afternoon peak is lacking from November till February, begins to form in March and reaches as much as 33.5% of total activity in September. The pause occurring at noon is most distinct during summer and vanishes gradually during the autumn months. Data from the field and from the cage show essentially the same pattern.Annual pattern: In the cage, activity is least during winter, increases gradually to a maximum in September followed by a sharp decrease to the winter minimum. The curve derived from the field observations shows a bimodal shape with a first peak in April and a second, more distinct one in September. A combination of the two groups of data shows three phases: December to May with irregular variations, May to September showing a conspicuous increase to maximal activity, September to December with sharp decrease to the winter minimum.