ATLANTA (AP) — The only panda born at a U.S. zoo so far this year was placed in an incubator on Monday for closer monitoring by zookeepers after visitors flocked to watch mother and child on a live video feed at Zoo Atlanta.

Zoo officials said in a release they wanted to more closely watch the tiny, hairless cub — which is the size of a stick of butter — based on the behavior of the cub and its mother, Lun Lun, in the zoo's birthing den.

The panda cub, the gender of which hasn't yet been determined, was born Saturday, just a week before the second birthday of Mei Lan, the zoo's first panda cub.

Three other U.S. zoos house pandas, which are endangered: San Diego, Memphis and Washington, D.C.