Vegetables like cauliflower, brussel sprouts, cabbage, kale, and broccoli should also be offered in small amounts or avoided because these contain iodine binders that can cause thyroid problems. In addition to a varied diet, box turtles should receive calcium and vitamin supplementation once a week for adults and three times a week for juveniles. Calcium and vitamin supplements are available at reptile stores. Natural Hibernation Box turtle subspecies that originate from areas with cold winters should be allowed to hibernate as they would in the wild. There is anecdotal evidence that natural hibernation is essential for the well-being and longevity of box turtles.
Most box turtles sold in pet stores are wild caught adults and have a strong hibernation instinct.
Many wild caught adult box turtles will stop eating in the late fall, even if they are kept warm. Box turtles that are ready to hibernate refuse food and spend the majority of their time buried, unmoving, in the substrate of the enclosure. If housed outside, a box turtle that is ready to hibernate will find an appropriate site and remain there, usually buried at least half way in the ground. Outdoor box turtles must be watched carefully when they choose their hibernation site, make sure that the area they have chosen is safe from children, pets, flooding and freezing. Make careful note of the chosen site, it is easy to loose a buried box turtle in a large yard.