VIDEO: Six Flags' Lion, Tiger Cubs Mark First Birthdays

JACKSON, NJ — A year ago, they were a pair of fuzzy, cuddly balls of fur. Now, Nadya and Zuri are full-grown big cats, and Six Flags Great Adventure is celebrating the cubs' first birthday by releasing a new video of the pair.

Siberian tiger cub Nadya and African lion cub Zuri have been raised as “sisters,” despite being species that would typically never cross paths in the wild, safari officials said. Both species are endangered.

“Last year, the animal care team experienced a very unusual situation," said Dr. Ken Keiffer, a Six Flags veterinarian. "Within a week, an African lion and a Siberian tiger gave birth with a single female cub in each litter. These first-time mothers were unable to care for their newborns, so our team stepped in, feeding them up to six times a day and caring for them around the clock."

Each cub weighed about 3 pounds at birth, safari staff said. Now, the two weigh 150 pounds each. Nadya, the first tiger born at the safari in 13 years, is expected to reach a weight of about 400 pounds, staff said. Zuri is expected to reach 280 pounds.

"To help their socialization skills, we brought these two cubs together and formed one litter,” Keiffer said.

The cats continue to play, eat and snuggle together. During their birthday celebration, they took turns devouring their custom meat cakes and exploring the presents safari caretakers wrapped with pink paper.

The safari staff no longer physically interacts with the cats due to their strength and natural predatory behaviors, but video of the cats' "birthday party" shows the bond between them remains. The cats can be seen spending time at the fence near their caretakers, and the cubs loudly greeted their team of surrogate mothers.

Six Flags put together a video of the cubs; you can view it below:

Guests can see the cubs on Safari Off Road Adventure in the Tigris Asiana section when the park opens April.

Video and photo of the cubs via Six Flags Great Adventure