The Energy Cost of Burrowing by the Pocket Gopher Thomomys bottae

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Abstract
Thomomys bottae maintain body temperature ( ) at 36 ± 0.3 C at ambient temperatures ( ) between 5 and 25 C. At greater than 25 C increases with . Rate of oxygen consumption at below 25 C is described by the equation: (cm³/g·h) = 2.52-0.062 . Minimum resting oxygen consumption is 0.84 ± 0.16 cm³/g·h and occurs at between 28 and 30 C. Oxygen consumption during burrowing was measured in four different soil types and a cost-of-burrowing model developed to fit these data. The model can be used to estimate the energy devoted to burrowing by free-living pocket gophers. Energy cost of burrowing varies with soil density and cohesiveness, burrow size, and burrow structure. Depending on soil type, burrowing can require 360-3,400 times as much energy as moving the same distance across the surface. The high energy cost of burrowing suggests that energy conservation may be particularly important to fossorial animals. The low basal metabolic rates and thermal conductance can be viewed as adaptations to conserve energy rather than adaptations to heat stress. The cost-of-burrowing model should be generally applicable to other fossorial rodents.