Bart was an Alaskan Kodiak bear born on January 19, 1977 at the Baltimore Zoo. When Bart was five weeks old and weighed five pounds (2 kg), he was sold to Doug and Lynne Seus, who worked as animal trainers for films. The Seuses trained Bart using a reward and praise system. While still a cub, he appeared in the TV series The Life and Times of Grizzly Adams playing Adams' companion bear, Ben, as a cub.

After reaching adulthood, he made his film debut in the film Windwalker (released 1981). He grew to 9' 7.5" (2.90 m) tall and weighed 1,500 pounds (680 kg) throughout his life as an adult.