Seasonal influences on burrowing activity of a subterranean rodent, Thomomys bottae

While many animals respond to seasonal variation in their environment, animals such as pocket gophers Thomomys bottae that live below ground might seem to be buffered against such variation. In some areas, however, the patterns of burrowing activity by pocket gophers are tied to the seasons, one factor of which is rainfall. Variation in activity patterns may result from the ease of digging in moist soil or increased food availability during the wet season. Previous simulation modelling work suggests that food availability influences burrowing patterns, while soil conditions do not. Thus, field experiments were used to investigate how soil conditions and food availability influence seasonal burrowing activity. Results indicate that an increase in soil moisture initiates activity. After this initial increase in activity, mound production declines and reaches a steady rate, which can be supported by vegetation availability, in agreement with previous model results. Our findings support the idea that moist soil promotes a burst of digging activity, potentially for burrow maintenance when soil becomes easily workable, and the eventual growth of vegetation provides the food necessary to support continued activity.