A rare leucism mutation is the cause of the unique joey's white coloring.

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Visitors to Animal Adventure Park who are looking forward to seeing the kangaroos are in for a special treat.

In a Friday Facebook post — with a caption beginning, "Our Jaws Are on the Floor!" — the Harpursville, New York-based zoo revealed that one of their red kangaroos, Rosie, had given birth to a rare, all-white joey (her first baby born at the park) a few months ago.

"At the age of approximately 4-5 months, we do our first full 'pull,' removing the baby from mom's pouch for a full inspection and medical review, and then return the joey to mom's pouch for her to raise," the zoo explained of how the baby's surprising coloring was discovered.

"Today's inspection revealed an extremely rare, what we are currently considering, leucistic male joey," the post continued.

Photos in the post show the adorable marsupial being cradled by handlers and held up in front of a full-grown red kangaroo: his dad, Boomer.

The park went on to explain that the joey's coloring is caused by a rare "lack of color pigmentation," and that his black eyes are what make him leucistic as opposed to "your normally anticipated red-eyed albino mutation."

"We are not aware of any leucistic red kangaroo in the United States, proving just how rare this occurrence is!" the caption continued. "That said, we are now working with professionals in the zoological community to see just how unique of a blessing this little one is!"

In the post, the park said that the joey's coloration was "a surprise to us all," and was caused by the genetic combination between his parents, Rosie and Boomer.

They also revealed that they waited until now to inspect the joey fully, as "red kangaroos are born the size of your thumbnail and do much of their development in mom's pouch, outside of the womb."

"What a remarkable day!" the caption on the discovery concluded.

This story originally appeared on People.com.