COLUMBUS (WCMH) — The Columbus Zoo says two cheetah cubs born through in vitro fertilization are continuing to grow and do well.

The cubs are the first-ever born through in vitro fertilization.

According to the Columbus Zoo and Aquarium, the cheetahs are now being reared by the zoo’s animal care team after checkups indicated the female cub was not gaining enough weight.

“The Columbus Zoo team has extensive experience in hand rearing cheetahs that require intervention, including the cubs’ mother, Izzy, and her litter mates. The cheetah cubs are currently being fed every four hours around the clock,” the zoo said in a Facebook post.

Both cheetahs need to be reared by the care team, since a mother cheetah’s milk will dry up when only caring for one cub.

The male cub weighs 2.2 pounds and his eyes and ears are open. The female cub weighs 1.7 pounds and her eyes and ears are just starting to open. The zoo says the cubs are crawling and interacting with each other.

The zoo says the cubs’ mother, Izzy, is allowing the care team to express milk from her. Samples of her milk will be contributed to the Smithsonian’s National Zoo and Conservation Biology Institute milk repository.

“With more than 15,000 samples of milks from over 150 species, it is the most extensive collection of exotic animal milk in the United States. Information gathered from milk samples contributes data for developing formulas for newborn animals that are unable to feed from their mother,” the zoo said.