Fig. 1. Schematic of burrowing apparatus with distance measurements. Distance from the starting end of the tube was recorded to the nearest tenth of a centimeter at the commencement of burrowing (S) and when the gopher reached the end of the tube or stopped burrowing consistently (T). The total distance burrowed (D) was then calculated as D=T–S. In cases where the gopher did not push all of the sand out of the tube and into the chamber, the amount of the tube that was filled with sand (F) was also recorded to the nearest tenth of a centimeter.