Fig. 5. The distribution of voluntary running speeds in deer mice tested at different ambient temperatures (T_a), expressed as time spent (A) and distance traveled (B) at different speeds. Data are 1 min averages, with different points from each animal separated by at least 3 min (see text). The same 32 animals were tested at each T_a, although some individuals ran very little at particular T_a and the number of data points varied among individuals. Downward-pointing arrows (in A) indicate the mean running speed for each T_a, calculated as (cumulative distance/cumulative run) time in 24 h (Table 4). The bin size was 0.068 km h^-1 (1 r.p.m. of wheel rotation). For clarity, speeds under 0.068 km h^-1 are not shown.