ST. LOUIS —  Five rare tiger cubs have been born at the Saint Louis Zoo.

The zoo says the critically endangered Amur (ah-MOOR') tigers were born April 28 and are in an off-display indoor den.

The zoo says the first-time mother, Kalista, is busy nursing and caring for her babies.

The normal litter size is two or three cubs. The five weigh 4.5 to 7 pounds each.

The species used to be called Siberian tigers. They are at risk because of habitat loss, human encroachment and poaching.

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