African lions and leopards are not what you'd call friends. In fact, lions have a habit of killing leopards.

So it was quite surprising when a five-year-old lioness was seen nursing a weeks-old leopard cub recently in Tanzania's Ngorongoro Conservation Area.

“It’s unprecedented,” says Luke Hunter, president and chief conservation officer for Panthera, a global wild cat nonprofit. “We never see this in the wild.”

View Images It's possible the maternal instincts of the lioness kicked in and overrode the usual instinct to kill a leopard cub. Photograph by Joop van der Linde, Ndutu Lodge

It’s unclear exactly how the lion and the leopard came into contact, or where the leopard’s true mother might be, but for now, Hunter says it seems as though the lioness’s aggressive instincts have taken a back seat to her maternal ones. (See "A Lioness Killing a Leopard Cub Floored These Filmmakers.")

You see, this female lion, known as Nosikitok, also has a few cubs of her own hidden in the bush. What’s more, the lion cubs are almost the same age as the leopard cub, according to KopeLion, the Tanzanian conservation nonprofit that has been tracking Nosikitok by radio-collar.

While the arrangement is unusual, Hunter says there’s nothing physiologically that should prevent the lion from raising the leopard. Both species produce similar milk and undergo comparable nursing periods. But these are not the only factors to consider.

“This is all speculation, and I’m hoping for the best,” says Hunter, “but I think the challenges to this little fellow surviving are really immense.”

Surviving the Gauntlet

While it’s not impossible, if the leopard cub were to survive, here’s what would have to happen.

Behind the Scenes: Death of a Leopard Cub See how Nat Geo WILD's Savage Kingdom filmmakers caught a lionness killing a leopard cub on camera.

First, Hunter says the lioness would have to bring the cub back to her litter. Right now, the only photos we have show the lioness nursing the leopard out in the open. But eventually, she will return to her den where several other hungry mouths await.

Even if the other cubs don’t put up too much of a fuss and the lioness continues to nurse the leopard, the denning period is no cake walk.

Thanks to other threats such as hyenas and wildfires, Hunter says the mortality rate for a lion litter in their first year averages is about 50 percent. (See" 14 Incredible Photos of African Predators in Action.")

View Images It's unknown what happened to the leopard cub's mother. Photograph by Joop van der Linde, Ndutu Lodge

“So the odds are against this poor little thing even if it becomes part of her litter, just because the litter itself might not survive the den period,” he says.

Next, the leopard kitten would need to be welcomed into the lion pride. Female lions go off on their own to give birth, but then return to the group when the cubs are around six to eight weeks of age.

At this point, it’s pretty likely that the rest of the lions—possessing neither the lionesses maternal hormones nor whatever connection she may have developed while nursing the cub—would kill the leopard on sight.

Against the Odds

And even if that doesn't happen, the story comes to a similar end. In a normal situation, a leopard would remain with its mother until 12 to 14 months, however some orphans have been known to survive on their own at seven to eight months.

If the leopard survives long enough to be brought back to the pride, it will be just two months old—still much too young to survive on its own.

“Lion females are incredibly devoted and diligent mothers,” says Hunter.

But even with the best adoptive mother in the world, it might require a bit of a miracle for this story to end on a note as adorable as it began.