Updated

Zookeepers are searching for a red panda that has gone missing from its enclosure in Washington.

National Zoo spokeswoman Pamela Baker-Masson says animal keepers discovered the male named Rusty was missing Monday morning. They began searching the zoo at 8 a.m.

Unlike giant pandas, red pandas are not members of the bear family. Red pandas are slightly bigger than a domestic cat and look similar to a raccoon. They are listed as vulnerable in the wild.

Red pandas are highly territorial, so Baker-Masson says it's unlikely that Rusty traveled far. He is likely hiding high in a tree branch to hide in the tree canopy.

"Everybody continues to look for him," Baker-Masson said. "As the day heats up, he will likely sleep and hide."

Animal keepers last saw him Sunday evening about 6 p.m. when he was fed and appeared healthy. They believe he may stay in hiding during the day. They are also looking at the possibility that Rusty is sick or that someone took him.

Rusty arrived at the zoo in April from the zoo in Lincoln, Neb., and was in quarantine for several weeks until he went on exhibit in early June. Rusty is vaccinated and is not aggressive, but he is a wild animal and could bite if he became cornered and scared, Baker-Masson said.

The zoo began sending out messages about his disappearance Monday morning on Twitter in case someone sees him at the zoo.

"Unless he was very motivated, he would not wander far from his habitat," Baker-Masson said. "This red panda is not down on the (National) Mall."