Abandoned newborn Amur tiger triplets are being cared for in an incubator at the Columbus Zoo and Aquarium's Animal Health Center.

Staff at the health center are keeping a special eye on the three male cubs, as they are from a critically endangered species. Zoo officials claim there are fewer than 400 left in the Russian Far East.

Before the birth of the rare cubs, it was hard to believe that their mom, Irisa, would ever conceive.

Irisa is an elderly tiger (10-years-old) and she has one undersized ovary so there were a lot of odds against her, Harry Peachey, curator of Asia Quest at the Columbus Zoo, told Live Science.

Irisa eventually bred with Foli, 11.

When Irisa was nearly in labor she was acting "abnormal" by not going into privacy like most other tigers do when they are about to give birth, Peachey told Live Science.

"She did nurse one cub, but she didn't nurse the other two," Peachey told Live Science. "And she wasn't bringing them toward her. She wasn't doing all the things that we regard as normal maternal behavior."

When zoo officials saw that Irisa wasn't acting like a mother towards her cubs they brought the 2.5-pound tigers to the incubator, where they are being closely cared for by experienced humans.