Officials at Essex County's Turtle Back Zoo briefly shut it down late Sunday morning after staffers noticed Megan, an Amur leopard, did not appear to be in her enclosure.
She was soon found hiding behind a retaining wall in a zoo service building and officials say she was never out among the general public. But as a precaution, the West Orange zoo was put on lockdown and patrons were moved to safe areas.
The zoo was closed for about 45 minutes while staffers sedated the leopard, which has lived there for about four years. It was later taken to an animal hospital for evaluation.
No injuries were reported in the incident.
