Authorities in West Orange closed the Turtle Back Zoo to visitors before it opened for the day.
Police scoured the zoo after officials feared that Megan, an Amur leopard, may have escaped.
It turns out Megan was just hiding behind a retaining wall inside its enclosure.
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.
