The general consensus in southern California seems to be that desert tortoises should not be allowed to hibernate during their first winter. However, I feel that if you choose to hibernate your hatchlings in their first year they can survive and prosper.
In September 1980 I had three hatchlings emerge from a clutch of 6 eggs. Val was measured on 9/18 and weighed 19.5g. Naomi and Tori were weighed on 9/21 and were 25.4 g and 24.8 g respectively. Through the middle of September to the end of October all three ate and gained weight. On 10/27 Val weighed 24.1 g, Naomi weighed 30.8 g and Tori weighed 29.6 g. All three had been kept in a terrarium in a shop area separated from the house and removed from any central heating system. Sometime in November the temperature dropped and all three tortoises became inactive. Val was in a cement pipe and did not emerge after this cold spell. I decided to leave Val in the shop for the winter, and moved Naomi and Tori into the house and into a glass terrarium with a hot rock.
Each tortoise was weighed once a month. As might be expected, Val dropped in weight by about 1 g each month. Both Naomi and Tori averaged around 30 g during this period. By February of 1981 the temperature increased enough to bring Val out of hibernation; on 1/27 Val weighed 20.7 g and increased to 24.5 g on 2/27. In this month Val regained the weight lost during the hibernation period. Naomi and Tori did not do as well. Naomi weighed slightly less on 2/27 (30.2 g) than back in October; Tori weighed slightly more (30.3 g on 2/27).
Unfortunately, both Naomi and Tori were found dead on their hot rocks shortly after this last measurement. My guess is that the brief cold spell may have stimulated all three tortoises to become inactive, and diminished their appetite. Val was able to survive this period by hibernating. However, Naomi and Tori remained fully active, but with a reduced appetite.