We quantified movements, spacing, and activity of Sonoran Mud Turtles (Kinosternon sonoriense) in interrupted mountain streams of southern Arizona over an 18-year period using capture–recapture sampling and radiotelemetry. Movement and activity patterns of turtles depended on water availability and varied by their sex and size. Although considered almost entirely aquatic in Arizona, mud turtles estivated terrestrially during periods of extreme drought. After the onset of summer rains, turtles increased the frequency with which they moved between pools and to nesting sites. Movements (average distance moved [AvD] ± SE) of all turtles were shorter during drought years (males = 26 ± 1.3 m, females = 19 ± 1.3 m) than non-drought years (males = 153 ± 1.2 m; females = 41 ± 1.2 m). Adult male turtles made longer movements (93 ± 1.2) and had longer home-range lengths (206 ± 1.2 m) than did adult females (AvD = 38 ± 1.2; home range = 40 ± 1.2 m). Younger adult females (carapace length [CL] 100–118 mm) made longer movements (52 ± 1.2 m) and had longer home ranges (80 ± 1.9 m) than did older females (>118 CL mm; AvD = 38 ± 1.2 m; home range = 26 ± 2.2 m). Males made movements >500 m more frequently (8%) than females (2%) and moved as far as 7.2 km as measured along drainage bottoms. Large turtles used pools exclusively, only rarely sharing pools with other large individuals of the same sex. Degradation and losses of interior wetlands in the southwestern U.S. have reduced the potential for long-distance movements of turtles among disjunct, remnant populations, which has consequences for conservation of turtles and other aquatic species in the region.