Washington (CNN) -- Rusty the runaway red panda is home and "doing great," according to Washington's National Zoo, but the question remains -- how did he escape?
Rusty, who is not even a year old, still has everyone stumped. The zoo exhibit has housed red pandas for several years without any problems, and Rusty's companion, 5-year-old Shama,remained in the zoo habitat when Rusty disappeared.
The habitat is designed, as a zoo official explained, to keep the red pandas in and humans out.
So how did Rusty find himself more than half a mile from the zoo in a residential area this past Monday?
Experts have evaluated the habitat and still have yet to determine a plausible route for Rusty's escape.
Pamela Baker-Masson, director of communications at National Zoo, said that zoo officials have "started the assessment of the enclosure, and it is likely we will have some short-term immediate actions and some long-terms actions."
The problem is, they aren't sure yet what those actions should be. Since red pandas are naturally arboreal animals, and spend much of their time in trees, the first step has been to assess the trees near the exhibit.
Since Monday, many of the trees around the red panda habitat have been trimmed but zoo staff still haven't located any branches that appear long enough for Rusty to have climbed out of his exhibit.
Since being captured and returned to the zoo, Rusty has been in the veterinary hospital undergoing health evaluations. Zoo veterinarians plan to keep him there through the end of the week but say he is eating and drinking normally and will be ready to return to his exhibit soon.
And he'll stay there -- as long as they can find a way to keep this escape artist from making another run for it.