In the Bolivian Chaco, the tortoise Chelonoidis carbonaria is an important reptile for indigenous people for subsistence purposes and in traditional medicine. This article describes research on seasonal activity, daily activity, and burrow use for the species at two long-term research camps in the Kaa-Iya del Gran Chaco National Park. The principal research method is the use of internal and external temperature dataloggers in 15 individuals over a two-year period. Tortoises reduce their activity in the dry season, and are not active when air temperatures are below 20^°C or above 37°C, though they can be active outside burrows at any time of year. Body temperature varies from 4°C in winter (monthly average of minimum daily temperatures) to 38°C in summer (monthly average of maximum daily temperatures). The instantaneous difference between body and environmental temperature could be as great as -23°C or 12^°C, but the monthly average was between -2°C and 4°C. Tortoises rely principally on shelters including fallen trees, dense bromeliad ground cover, and leaf mulch; but also use armadillo burrows and rock crevices. They use multiple shelters / burrows over time, occasionally sharing shelters with other individuals. Burrow use is important both in cold periods as well as in hot and dry periods. The dataloggers provided extremely detailed data on body and environmental temperature, but the implantation caused problems in several individuals and the procedure may need modifications.