>> the biggest danger is if he ate inappropriate food. >> reporter: bamboo or treats prepared by his keepers. for the moment, rusty has no visible signs of injury or illness. we pressed a zoo spokeswoman on another key question. how in the world do you lose a red panda, how did it happen? >> we don't know right now, complete honesty, we do not know. that habitat has housed red pandas several years. no one has escaped before. the habitat is constructed to keep red pandas in and people out. >> reporter: a possible clue, red pandas are called natural climbers, tree dwellers. could rusty have used a tree to climb out of the exhibit behind me? the team came here after he escaped and found no obvious route out, but they are not ruling it out as a possibility and one possibility could be here, the electric fence, there is a tree up there on one side of the electric fence that kind of hangs over. that could have been one of the escape routes. zoo zo officials say they'll