Kavanau, J. L., Rischer, C. E. 1968. Program clocks in small mammals. Science 161, 1256-1259.
Given access to an activity wheel, small mammals spend almost all their active time running it. ... If the instantaneous speed and direction of running are recorded every seconds on a moving chart, the activity patterns obtained rival sonographs of bird songs in their richness of individuals and species detail.
Year
1968