The alligator is missing many teeth, while other teeth in its mouth were broken or infected.
Harrison said the alligator is just under 7 feet long, but should be more like 10 feet long. He said it showed other signs of malnourishment and lack of vitamin D from being kept in a basement for 15 years without sunlight.
"When we brought him out in to the sun, he actually just closed his eyes for a long time. It was really sad," he said.
The alligator, now being allowed out in the sun in Columbus, will be moved to a refuge in Florida this week, where he'll get special care, and be kept in a swampy, outdoor area, Harrison said, adding that an alligator's average life span is about 75 years old in captivity.
"He's going to be an alligator the best he can be," he said.