RELATION OF SEASONAL ACTIVITY PATTERNS OF VALLEY POCKET GOPHERS TO TEMPERATURE, RAINFALL, AND FOOD AVAILABILITY

We analyzed trapping success, reproductive status, surface-heap deposition, surface-access tunneling, and clearing of experimentally plugged tunnels to determine the relation of activity of Thomomys bottae to air temperature, rainfall, and food availability in a mima-mound and vernal-pool habitat in San Diego, California. All activities varied seasonally. Trapping success and clearing of plugged tunnels, reflecting use and maintenance of tunnels, were negatively correlated with air temperature for the preceding week and time since rainfall of greater-than-or-equal-to 2.5 mm. Surface heaps, an indicator of expansion of the main tunnel system, were weakly correlated with the same variables. Production of surface-access tunnels did not correlate with either temperature or rainfall, but peaked late spring-early summer at the end of the growing season. Expansion of the main tunnel system is favored by moist soil and cool temperatures, but probably is triggered by growth of herbaceous food plants and recrudescence of sexual activity, whereas digging of surface-access tunnels is related directly to availability of harvestable aboveground foods.