From the Orlando Sentinel.... Disney's Animal Kingdom is working on a tiny mystery. Lilly, a western lowland gorilla born at the theme park last year, is very small. She weighs just 10 pounds, less than half of what a gorilla her age should weigh. Disney's Animal Programs team hasn't determined the source of her underdevelopment. There's no sign of another case like hers, so team members are giving Lilly the kind of occupational therapy typically reserved for human children who are developmentally challenged. Lilly was born to first-time mother Kashata in February after a normal pregnancy, said Barb Weber, primate zoological manager. Trainers noticed the new mom was helping her offspring much longer than expected. Kashata "always kept a hand supporting Lilly," Weber said. "It actually continued for months where a couple of days would be normal." Lilly also had difficulty gripping objects â€” a necessity for gorillas in order to grab, climb and feed themselves â€” and nursing. "Sometimes Lilly looked like she didn't have the strength or was just too tired to latch on to the nipple, so Kashata would position herself to make it very easy for Lilly," Weber said. Routine medical tests were done at Animal Kingdom, followed by consultations with outside experts and specialists â€” both veterinary and human doctors. Lilly even went on a field trip to Florida Hospital Celebration, where she had an MRI and saw pediatric neurologists, radiologists and other medical professionals. "The great news is we haven't found anything that was really scary," said Dr. Mark Stetter, director of animal health for Disney's Animal Programs. "But at the same time, we have checked off many, many, many, many things," including vitamin D deficiency; water on the brain; hypothyroid issues; heart disorder; brain and liver abnormalities; dwarfism; and Down syndrome. The emphasis switched from diagnosis to improving Lilly's quality of life. In June, Marzena Batignani, a licensed occupational therapist who usually works with children suffering from autism, cerebral palsy and spina bifida, began weekly sessions with the young gorilla at Animal Kingdom. Batignani met a lackadaisical Lilly, who had trouble eating. "She had a very hard time controlling the food in her mouth because her tongue would push it out," she said. Batignani and the Disney team started rubbing an electric toothbrush across Lilly's jaws, face, neck and upper arms. The vibration is "very awakening and alerting" to the body's systems that organize the brain and the body, Batignani said. The mouth is a key area for development, Batignani said. "It takes items in, and it disseminates a lot of information," she said. "It will stimulate the brain to start focusing on both the items in the mouth and bring focus to things in their environment." Disney caretakers hold therapy sessions twice a day with Lilly. They use toys and food to encourage her to multitask and develop strength in her lagging left side. "She's doing much, much more. â€¦ What we're trying to get her to do is hold something, then grab something else at the same time," Batignani said. Sometimes Lilly is mellow during the sessions, content to sit and eat walnuts. Other days, she climbs up the side of their backstage enclosure, using her improved grip to reach for rewards, all under the eye of mother Kashata. "She will make her climb when she thinks it's necessary and take her down when she thinks it's dangerous," Batignani said. "She's the best therapist that Lilly could have asked for." It may be hard to find a gorilla with similar circumstances because there are only 10 to 15 births per year in the United States, said Kristen Lukas, chair of the Gorilla Species Survival Plan of the Association of Zoos and Aquariums. About 350 gorillas are living in 52 North American zoos accredited by the zoo association. Kashata, Lilly and Lilly's father, Gino, are among the nine gorillas living at Animal Kingdom. Disney officials are encouraged by Lilly's progress. She can be seen by Animal Kingdom guests along its Pangani Forest Exploration Trail. "I think we were in a much heightened stage of concern and worry six months ago," said Stetter, Disney's director of animal health. "We're probably less now, but she's still not right. â€¦ We're still concerned." The lack of answers makes Lilly's minders unwilling to put a label on her condition. "You can't compare her to others. We know something is unusual with her, not necessarily bad, but unusual," said Batignani, the therapist. "What we look at is, 'Is Lilly in January different from Lilly in September?' If we can say yes, then no matter what, we've done a great job."